‘w-a “3!inle Michigan State University This is to certify that the dissertation entitled SYNTHESIS OF EXTENDED TRIPTYCENES(IPTYCENES) AND LINEAR POLYCYCLIC ARENES presented by J ihmei Luo has been accepted towards fulfillment of the requirements for Ph. D. degree in CHEMISTRY #W #5 Major professor Dme Oct.30,1986 MCI/i“... Ah“; 4 - r‘ lrL . . . . 0.12771 MSU LIBRARIES “ RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if Soofi is returned after the date stamped below. r-u SW18 0' EXTENDED Truman: amen”) AND LINEAR POLICYCLIC AIINZS Jihnei [no A DISSERTATION submitted to Inchigan State University in partial mtillnent ot the require-ant for the degree of NCTOR OP PHIIOSOPH! Department of Chemistry 1986 '42s“. 37mg ABSTRACT SYNTHESIS OF EXTENDED TRIPTYCENES (IPTYCENES) AND LINEAR POLHCYCLIC ARENES Jihnei Luo Triptycene is the first member of a large series of compounds for which we have coined the general term "iptycene". The prefix (tri, pent,_ etc.) indicates the number of separated arene planes. A general synthetic approach to the iptycene framework and the synthesis of some specific iptycenes are described. Four useful iptycene synthons can be derived from 1,2,4,5-tetrabromobenzene 31. Treatment of 31 with either one or two equivalents of n-BuLi and furan gives 6,7- dibromo-l,4-dihydronaphtha1ene-1,4-epoxide 38 or 1,4:5,8- diepoxy-1,4,5,8-tetrahydroanthracene 40. Metal-catalyzed deoxygenation of 38 gives 2,3-dibromonaphthalene 49, which is then treated with one equivalent of n-BuLi and furan to give 1,4-dihydroanthracene-1,4-epoxide 50. The utility of the above five synthons and of 1,4-dihydronaphthalene-1,4- epoxide 7, and 11,12-dimethy1ene-9,lO-dihydro-9,lo-ethano- anthracene 52 is demonstrated in four new, much improved Jihmei Luo syntheses of 5,14[1',2'Jbenzeno-S,14-dihydropentacene 20, itself a useful iptycene synthon. The versatility of 20 as a synthon for higher iptycenes is illustrated with syntheses of six pentiptycenes, two heptiptycenes and two noniptycenes. In the second part of this thesis, the synthesis of linear polycyclic epoxyarenes by cycloaddition of benzo- cyclobutene to the epoxides 7,38,40 and 50 was investigated. Dehydration followed by dehydrogenation of the corresponding adducts affords a convenient way to prepare linear acenes (i.e. tetracene, 2,3-dibromotetracene and pentacene) in good yields. Cycloaddition of 5,14-dihydropentacene 128 with so or 38, followed by dehydration and dehydrogenation, gives the potential synthon 7,16[1',2']benzeno-7,16-dihydro- heptacene 109 or 6,15[1',2']benzeno-2,3-dibromo-6,15- dihydrohexacene 143. The dual functionalities present in these molecules should permit their use as precursors of complex iptycenes or polyiptycenes. A synthetic equivalent of furano[3,4-f]benzo[c]furan 133 is described in the third part of this thesis. Cycloaddition ,of 40 and tetraphenylcyclopentadienone 153 gives bis-adducts 160 in high yield. Thermal decomposition of 160 in the presence of a dienophile (i.e. DMAD, TCNE, naphthaquinone, 1,4-anthraquinone and 7) provides a novel route to linear polycyclic epoxyarenes in good yields. With Love, to Thungmei ACKNOWLEDGEMENTS I wish to express my sincere appreciation to Professor Harold Hart for his enthusiasm, encouragement and guidance throughout the course of this study. In addition, I would like to thank Professor E. G. LeGoff, who served as my second reader, and the other members of my Guidance Committee, Professor G. E. Leroi and Professor T. J. Pinnavaia. ‘ Appreciation is extended to Michigan State University, the National Science Foundation, and the National Institutes of Health for financial support in the form of teaching and research assistantships, and the SOHIO company for a summer term fellowship. Many thanks go to my family, parents-in-law, and friends for their love and support over the past few years. Last and most, I thank my wife, Thungmei, for her endless love, support, and encouragement during these years. TABLE OF CONTENTS Chapter . page LIST OF TABLE 0 O O O O O O O O O O O O O O O O O I a 0 X LIST OF FIGURES O O O O O O O O O O O O O O O O O O O O Xi APPENDICES. . . . . . . . . . . . . . . . . . . . . . . xii INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . 1 RESULTS AND DISCUSSION. . . . . . . . . . . . . . . . . 14 Part I. Synthesis of Extended Triptycenes (Iptycenes). . . . . . . . . . . . . . . . . 14 A. Useful Synthons. . . .'. . . . . . . . . . . 14 B. Exo Selectivity in Endoxide Cyclo- additions. . . . . . . . . . . . . . . . . . 20 C. An Improved Synthesis of [3(b,b)b.1.1]- Triptycene (20). . . . . . . . . . . . . . . 21 Method A. . . . . . . . . . . . . . . . . . 23 Method B. . . . . . . . . . . . . . . . . . 24' Method C. . . . . . . . . . . . . . . . . . 25 Method D. . . . . . . . . . . . . . . . . . 26 D. Cycloadditions of [3(b,b)b.1.1]Triptycene (20) with TCNE, DMAD and MA. . . . . . . . . 27 E. Synthesis of a Series of [nb.1.1b.1.1]- Pentiptycenes via 20. . . . . . . . . . . . 29 1. [1.1.1b.1.1]Pentiptycene (24). . . . . . 29 2. [2b.1.1b.1.1]Pentiptycene (76). . . . . . 31 3. 5,16[1',2']:7,14[1",2"]Dibenzeno-10,11- dibromo-5,7,14,16-tetrahydrohexacene (78). . . . . . . . . . . . . . . . . . . 33 iv Chapter page 4. [3(b,b)b.1.1b.1.1]Pentiptycene (81). . . . 34 5. 7,12[1',2']Benzeno-15,16-dimethylene- 5,14-ethano-5,7,12,14-tetrahydro- pentacene (83). . . . . . . . . . . . . . 35 6. 5,18[1',2']:7,16[1",2"]Dibenzeno-11,12- dibromo-5,7,16,18-tetrahydroheptacene (86). . . . . . . . . . . . . . . . . . . 38 7. Dimethyl 5,14[1',2']:7,12[1",2"]diben- zeno-5,7,12,14-tetrahydropentacene-2,3- dicarboxylate (88). . . . . . . . . . . . 39 F. Synthesis of [1.1.3(b,b)b.1.1b.1.1]- Heptiptycene (90). . . . . . . . . . . . . . 40 b.103(b’b)be 101b01011- G. Synthesis of [1.1.1 Noniptycene (98 and 103). . . . . . . . . . 44 H. Synthesis of [4(b,b,b)b.1.1]Triptycene (108). . . . . . . . . . . . . . . . . . . . 49 I. Conclusions. . . . . . . . . . . . . . . . . 50 Part II. Synthesis of Linear Acenes and Polyiptycene Precursors. . . . . . . . . . 52 A. Attemped Synthesis of [3(b,b)b.1.3(b,b)b]- Triptycene and [3(b,b)b.3(b,b)b.3(b,b)b]- Triptycene via a Heptacene Equivalent. . . . 52 B. Synthesis of Tetracenes (15 and 127) and Pentacene (10). . . . . . . . . . . . . . . 58 C. Isobenzofuran Intermediates Observed from the Mass Spectra of Epoxyarenes. . . . . . . 66 V Chapter page D. Synthesis of [3(b,b)b.l.3(b,b)b]Triptycene (109) via 5,14-Dihydropentacene. . . . . . . 68 E. Synthesis of 6,15[1',2']Benzeno-2,3- dibromo-6,15-dihydrohexacene (143) via 5,14-Dihydropentacene. . . . . . . . . . . 72 F. Conclusions. . . . . . . . . . . . . . . . . 75 Part III. Synthesis and Reactions of a Furano- [3,4-f]benzo[c]furan Equivalent. . . . . 76 A. Synthesis of Furano[3,4-f]benzo[c]furan Equivalent (160). . . . . . . . . . . . . . 79 B. Trapping Various Dienophiles with Furano- [3,4-f]benzo[c]furan Equivalent. . . . . . . 80 C. Mechanism for the Generation of Isobenzo- furan or Furano[3,4-f]benzo[c]furan from 160a. . . . . . . . . . . . . . . . . . . . 85 D. Suggestions for Further Studies. . . . . . . 87 EXPERIMENTAL 1. General Procedure. . . . . . . . . . . . . . . 90 2. 1,2,4,5-Tetrabromobenzene (31). . . . . . . . . 9o 3. 6,7-Dibromo-1,4-dihydronaphthalene-1,4- epoxide (38). . . . . . . . . . . . . . . . . . 91 4. 2,3-Dibromonaphthalene (49). . . . . . . . . . 91 5. 1,3-Dibromonaphthalene (55). . . . . . . . . . 92 6. 1,4-Dihydroanthracene-1,4-epoxide (50). . . . . 92 7. 11,lZ-Dimethylene-9,10-dihydro-9,10- ethanoanthracene (52). . . . . . . . . . . . . 93 vi Chapter 10. 11. 12. 13. 14. is. 16. 17. 18. 19. page 1,4:5,8-Diepoxy-1,4,5,8-tetrahydro- ranthracene (40). . . . . . . . . . . . . . . . 94 5,14[1',2']Benzeno-5,14-dihydropentacene (20). . . . . . . . . . . . . . . . . . . . . . 94 Diels-Alder adduct of 20 with tetracyano- ethylene (69). . . . . . . . . . . . . . . . . 99 Dials-Alder adduct of 20 with dimethyl acetylenedicarboxylate (70). . . . . . . . . . 99 Diels-Alder adduct of 20 with maleic anhydride (71). . . . . . . . . . . . . . . . . 100 5,14[l',2']:7,12[1",2"]Dibenzeno—5,7,12,14- tetrahydropentacene (24). . . . . . . . . . . . 100 5,16[1',2']:7,14[1",2"]Dibenzeno-5,7,14,16- tetrahydrohexacene (76). . . . . . . . . . . . 101 5,16[1',2']:7,14[l",2"]Dibenzeno-10,ll- dibromo-5,7,14,16-tetrahydrohexacene (78). . . 102 5,18[1',2']:7,16[1",2"]Dibenzeno-5,7,16,18- tetrahydroheptacene (81). . . . . . . . . . . . 103 7,12[1',2']Benzeno-15,16-dimethy1ene-5,14- ethano-5,7,12,14-tetrahydropentacene (83). . . 104 5,18[1',2']:7,16(1",2"]Dibenzeno-11,12- dibromo-5,7,16,18-tetrahydroheptacene (86). . . 106 Dimethyl 5,14[1',2']:7,12[1",2"]dibenzeno- 5,7,12,14-tetrahydropentacene-2,3- dicarboxylate (88). . . . . . . . . . . . . . . 107 vh Chapter 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. page 5,22[1',2']:7,20[1",2"]:11,16[1'",2'"]- Tribenzeno-5,7,11,16,20,22-hexahydro- nonacene (90). . . . . . . . . . . . . . . . . 108 Diels-Alder adduct of 90 with DMAD (91). . . . 109 Syn-5,26[1',2']:7,24[l",2"]:11,20[l ,2 1: 13,18[1"",2"")tetrabenzeno-5,7,11,13,18,- 20,24,26-octahydroundecacene (98). . . . . ._. 109 Anti-5,26[1',2']:7,24[1",2"]:11,20[l ,2 1: 13,18[1"",2""1tetrabenzeno-5,7,11,13,18, 111 20,24,26-octahydroundecacene (103). . . 5,16[1',2'JBenzeno-S,16-dihydrohexacene (108). . . . . . . . . . . . . . . . . . . . . 112 Bis-cycloadducts of 40 and 114 (116). . . . . . 113 Dehydration of 1168 (112 and 113). . . . . . . 114 Attemped cycloaddition of 50 with 112. . . . . 116 Bis-cycloadducts of 40a and 119 (120). . . . . 116 Tetracene (15). . . . . . . . . . . . . . . . . 117 2,3-Dibromotetracene (127). . . . . . . . . . . 118 Pentacene (10). . . . . . . . . . . . . . . . . 119 7,16[1',2']Benzeno-7,16-dihydroheptacene (109). . . . . . . . . . . . . . . . . . . . . 120 Benzyne adduct of 109 (27). . . . . . . . . . . 121 6,15[1',2']Benzeno-2,3-dibromo-6,15- dihydrohexacene (143). . . . . . . . . . . . . 122 Benzyne adduct of 143 (78). . . . . . . . . . . 123 vfii Chapter 36. 37. 38. 39. 40. 41. 42. 43. 44. page Photodimer of [3(b,b)b.1.1]triptycene (139). . . . . . . . . . . . . . . . . . . . . 124 Bis-cycloadducts of 40 and 153 (160). . . . . . 124 Reaction of 160a with DMAD (162). . . . . . . . 125 Reaction of 160a with TCNE (163). . . . . . . . 126 Reaction of 160a with naphthaquinone (164). . . . . . . . . . . . . . . . . . . . . 126 Reaction of 160a with 1,4-anthraquinone (165). . . . . . . . . . . . . . . . . . . . . 126 Reaction of 160a with 1,4-dihydro- naphthalene-1,4—epoxide (166). . . . . . . . . 127 5,18:9,14-Heptacenediquinone (161). . . . . . . 127 6,21:10,17-Nonacenediquinone (171). . . . . . . 128 BIBLIOGRAPHY O O O O O O O O O O O O O O O O O O O O O O 147 LIST OF TABLES page Synthons Useful as Aryne or Di-aryne Equivalent. . . 16 1H NMR Spectra of [nb.1.1b.1.1]Pentiptycene. . . . . 36 Isobenzofuran Intermediates Observed in the Mass Spectra of Epoxyarenes. . . . . . . . . . . . . . . . 67 1. 10. 11. 12. 13. LIST OF FIGURES page Various iptycenes. . . . . . . . . . . . . . . . . 5 Synthesis of [1.1.1b.1.1b.1.1]heptiptycene 27 via 2,376,7-anthradiyne equivalent 40. . . . . . . 9 Synthesis of [3(b,b)b.1.1]triptycene 20 via 2,3;6,7-naphthadiyne equivalent 38. . . . . . . . . 10 General construction of the iptycene framework. . . 14 Synthesis of various synthons from 1,2,4,5- tetrabromobenzene 31. . . . . . . . . . . . . . . . 17 Exo and endo adducts of 7-oxabicyclo[2.2.1]hepta- 2,5-dienes 48 with anthracene. . . . . . . . . . . 20 Schematic syntheses of [3(b,b)b.1.1]triptycene 20 via various synthons. . . . . . . . . . . . . . 22 Schematic syntheses of [nb.1.lb.1.1]pent- iptycenes via [3(b,b)b.1.1]triptycene 20. . . . . . 30 Synthesis of [2b.1.1b .1.1]pentiptycene 76. . . . . 31 Synthesis of tetracenes (15,127) via epoxides (7,38) and benzocyclobutene 114. . . . . . . . . . 59 Generation and trapping of isobenzofuran intermediate 129. . . . . . . . . . . . . . . . . . 77 Trapping various dienophiles with furano[3,4-f]- benzo[c]furan equivalent 160a. . . . . . . . . . . 81 Possible mechanisms for the generation of isobenzofuran or furano[3,4-f]benzo[c]furan 133 intermediate from 160a. . . . . . . . . . . . . . . 86 xi 10. APPENDICES 250 MHz 1H NMR of 5,14[1',2']Benzeno-5,14- dihydropentacene (20). . . . . . . . . . . . 250 MHz 1H NMR of 5,16[1',2']Benzeno-5,16- dihydrohexacene (108). . . . . . . . . . . . 250 MHz 1H NMR of 5,14[1',2'];7,12[1n,2u]- Dibenzeno-5,7,12,14-tetrahydropentacene (24). 250 MHz 1H NMR of 5,l6[l',2']:7,14[1",2"]- Dibenzeno-5,7,14,16-tetrahydrohexacene (76). 250 MHz 1H NMR of 5,16[1',2']:7,14[1".2"]- Dibenzeno-lo,11-dibromo-5,7,14,16-tetrahydro- hexacene (78). . . . . . . . . . . . . . . . 250 MHz 1H NMR of Adducts 79 and so. . . . . 250 MHz 1H NMR of 5,18[1',2']:7,16[1",2"]- Dibenzeno-5,7,16,18-tetrahydroheptacene (81). 250 MHz 1H NMR of 7,12[1',2']Benzeno-15,16- dimethylene-S,14-ethano-5,7,12,14-tetrahydro- pentacene (83). . . . . . . . . . . . . . . 250 MHz 1H NMR of 5,18[1',2']:7,l6[1",2"]- Dibenzeno-ll,12-dibromo-5,7,16,18-tetrahydro- heptacene (86). . . . . . . . . . . . . . . 250 MHz 1H NMR of Dimethyl 5,14[1',2']: 7,12[l",2"]dibenzeno-5,7,12,14-tetrahydro- pentacene-2,3-dicarboxylate (88). . . . . . xfi page 129 130 131 132 133 134 135 136 137 138 11. 12. 13. 14. 15. 16. 17. 18. page 250 MHz 1H NMR of 5,22[1',2']:7,20[1",2"]: 11,16[lm,2"jTribenzeno-5,7,11,16,20,22- hexahydrononacene (90). . . . . . . . . . . . . . . 139 250 MHZ 1H NMR of DMAD adduct of 90 (91). . . . . . 140 250 MHz 1H NMR of Adducts 96 and 97. . . . . . . . . 141 250 MHz 1H NMR of Syn-5,26[1',2']:7,24[1",2"]: 11,20[1"22"U:13,18[1"",2""]tetrabenzeno- 5,7,11,13,18,20,24,26-octahydroundecacene (98). . . 142 250 MHz 1H NMR of Adducts 101 and 102. . . . . . .,. 143 250 MHz 1H NMR of Anti-5,26[1',2']:7,24[l",2"]: 11,20[1"22"fi:13,18[1"",2""]tetrabenzeno- 5,7,11,13,18,20,24,26-octahydroundecacene (103). . . 144 250 MHz 1H NMR of 7,16[1',2']Benzeno-7,l6- dihydroheptacene (109). . . . . . . . . . . . . . . 145 250 MHz 1H NMR of 6,15[l',2']Benzeno-2,3- dibromo-6,15-dihydrohexacene (143). . . . . . . . . 146 xfii INTRODUCTION A. Triptycene. Triptycene 11 was first synthesized in 1942 by P. D. Bartlett2 for the purpose of testing certain concepts in physical-organic chemistry. The trivial name is derived from the triptych of antiquity, a book with three leaves hinged on a common axis. The Bartlett synthesis, which started from 1,4-benzoquinone 2 and anthracene, was lengthy (7 steps) and gave 1 in only a modest overall yield (<20%). 7 steps ((20%) o ‘ a ‘2, M“ [6:91» mi)... ‘4,- , 1 step (61%) Some years later, a one-step synthesis from benzyne 4 (generated from the Grignard reagent of o-bromofluorobenzene 3) and anthracene 5 was developed by Wittig3, and really opened the door to triptycene chemistry. With the development of various benzyne precursors, it was found that 1 2 the most convenient way to generate benzyne for the preparation of triptycene is to decompose o-benzenediazonium carboxylate 6 (obtained by diazotising anthranilic acid) by heating in an aprotic solvent.4 This methodology made triptycene readily available for many interesting investigations. Numerous triptycenes are now known.5 Their rigid framework has attracted the attention of many research workers. In recent years, triptycenes have been used in 6 mechanistic studies and to study intramolecular charge transfer,7 restricted rotation about single bond (atropisomerism),8 and correlated bond rotations (gearing).9 A few triptycene analogues containing naphthalene, anthracene and other fused-rings have also been synthsized. In 1960, Wittiglo discovered that the furan adduct of benzyne, 1,4-dihydronaphthalene-1,4-epoxide 7 , was an effective dienophile. The double bond of 7 added to the ~x lene ’ @@@ 3{90%) 35?.(9 (9(4ch @0909 W 1333‘” 10 g"' :IkCRC) 3 middle ring of anthracene or pentacene to give adducts 8 or 11, respectively. The oxygen bridges were removed separately by acetic anhydride or hydrochloric acid in acetic anhydride to produce [2b.1.1]triptycene 9 or [2b.2b.2b]triptycene 12 (the derivation of the trivial names will be described; vide infra). In these two-step sequences, 7 acts as the synthetic equivalent of 2,3- naphthyne 13 in cycloadditions to acenes. This concept is important to us since we will apply this idea to the synthesis of extended triptycenes throughout the course of [00'] Other fused-ring triptycenes were used by Misumi11 to this study. 1 test the concept of transannular 1r- r interactions by examining their spectral properties. The syntheses were generally extensions of the Wittig concept, i.e. cycloaddition reactions of arynes and acenes. Althouugh the @ 5 ‘9 (11%) $06 9 ‘ 5 AKOO); @3 (24%) (35%) egg ‘6 «a...» we ”° 18 19 i 15 .AHK}<3§. ii} ”2915' (2 %) 0 9 90 2190 cycloadditions were successful, the yields were rather low. Morever, the aryne precursors (14 and 18) are not readily available (especially 18, which was prepared in five steps from toluene12 or obtained in a low yield, multi-step route from phthalic anhydride13 ). Compound 20 was attractive to us, since it may serve as a building block in the synthesis of extended triptycenes. We shall describe in this thesis several much better routes to 20. We can summarize these literature results by noting that the basic construction of the triptycene framework is generally through aryne (i.e. 4, 13, 19) addition to an acene(i.e. anthracene, tetracene, pentacene). B. Extended Triptycenes (Iptycenes). Despite this substantial history,5 the considerable potential for extending the rigid triptycene framework to larger interesting and useful compounds has only recently 14 been realized. Triptycene 1 is the parent of a large 5 series of compounds for which Hart has coined the general term " iptycene ".14a The name " iptycene " emphasizes the relationship between these compounds and the parent structure triptycene. A prefix indicates the number of separated arene planes; thus 1, 9 and 20 are triptycenes (three planes); 22, 24, 25 and 26 are pentiptycenes (five planes): 23 and 27 are heptiptycenes (seven planes). Figure 1. Various iptycenes. 6 There are three descriptors that need to be added to these names to precisely define the structures. The use of two of these descriptors is illustrated in the following names: for 22, [1.1.1a.1.1]pentiptycene; 24, [1.1.1b.1.1]- pentiptycene; ' 23, [1.1.1a'c.1.1.1.1]heptiptycene: 27, [1.1.1”.14b .1.1]heptiptycene; 9, [2b.1.1]triptycene. The 1's indicate that each ring is benzenoid, and this number would be replaced by 2 if naphthalenoid or 3 if anthracenoid or phenanthrenoid, etc. The superscriptors refer to the bond (a, b, or c) to which the sp3 carbons are attached. A third descriptor, to indicate points of ring fusion, may 3130 be necessary. It consists again of a bond (a, b, or c) and is placed in parentheses. For examples: for 25, [1.1.2(b)b.1.1]pentiptycene: 26, [1.1.3(b,b)b.1.1]- pentiptycene; 20, [3(b,b)b.1.1]triptycene. Just as with triptycenes, cycloaddition reactions will also be important in the construction of extended triptycenes (iptycenes). This methodology has been applied to the synthesis of several iptycenes using aryne or di- aryne equivalents. The pentiptycene 24 was first prepared by Russian workers by the reaction of triptycyne equivalent 28 with anthracene, in low yield (10%).15 The @ a 6 g F __M_g. ms 4 9‘ @a. 060 @’@‘© (10%) 23 24 7 required o-bromofluorotriptycene 28 was synthesized from anthracene in four steps, so that the overall yield of 24 from a readily available starting material was only 1.2% (5 steps). The di-t-butyl derivative 30 was synthesized from di- aryne precursor 29 but in only a 2% yield.16 .. em. 9 @ .. @oo * ’coo’ ? ~ 6 (9 (2%) 29 - so An improved method of generating di-aryne equivalents has been developed in recent years by Hart and coworkers.17 They described the use of tetrahaloarenes as di-aryne equivalents. When treated with two equivalents of an organolithium reagent in the presence of certain dienes, bis-cycloadducts were readily formed. For example, a simple one-step synthesis of 2414a in a much improved yield was executed using tetrabromobenzene 31 as a 1,4-benzadiyne equivalent. The yield in this reaction was 94% based on the consumed anthracene, but only 26% based on the tetrabromobenzene. 3‘ (9%) Br 3' BuLi Toluene R.T. Q (9 ar‘er > @’@‘© . Q 0 CH3 6 8' BuLi , Toluene, ~23'c ’ CH, CH. Br CH, 0. a; (14%) @ Br 3, BuLi ,. Toluene gage, Eh’l::,I::| 3, I:’<>(JI 34 (60%) Similarly, pentiptycenes 33 and 35 were synthesized via di-aryne equivalents 32 and 34, respectively.14a 1,2,4,5-Tetrabromobenzene 31 is an especially useful synthon, since it serves not only as the synthetic equivalent of 1,4-benzadiyne 36 and 4,5-dibromobenzyne 37, but also as the precursor of synthetic equivalents of 2,3;6,7-naphthadiyne 39 and 2,3;6,7-anthradiyne 41. Hart and coworkers demonstrated the use of this concept with syntheses of the novel iptycene 27 and the useful synthon 20 (vide infra). ”El" &' 3' 31 fig] [Z©' ] 37 II 9 Treatment of 31 with either one or two equivalents of n-butyllithium and furan gave epoxide 38 or bis-epoxide 40. 5 ECU] 1eq.BuuL.iI 31 + QLJ? -—-' [Jose 8! a!” 38 2eq.BufilF flfli‘liifln 40 41 Since the double bonds in 38 and 40 are effective dienophiles, these aryne equivalents can be used to build fused-ring iptycenes, such as 26 (Fig. 2) and 20 (Fig. 3). Cycloaddition of 40 with anthracene gave bis-adduct 42, which on dehydration produced pentiptycene 26. Thus, 40 is a synthetic equivalent of 2,336,7-anthradiyne 41. The. central anthracene moiety in 26 added benzyne to give the novel U-shape heptiptycene 27.14b a + ""°"° > ‘COOOG'Q (80%) 40 5 G? » .» HCI.AW _@__..@ 0 (41% Q ( 51%) 26 Figure 2. Synthesis of [1.1.1b.1.1b.1.1]heptiptycene 27 via 2,3:6,7-anthradiyne equivalent 40. 10 Similarly, 38 is a 2,336,7-naphthadiyne equivalent. Reaction of 38 with anthracene produced an adduct 43 which on dehydration gave 44. Treatment of 44 with one equivalent of n-butyllithium and furan gave an adduct 45 which was then deoxygenated with low-valent titanium to give [3(b,b)b.1.1]- 18 triptycene 20. This synthesis of 20 gives a much better yield than the literature method.11a Since compound 20 will serve as an important building block in the synthesis of higher iptycenes, we shall also describe later three other methods for its synthesis (see Results and Discussion part). c9 :1? + ’22:: e» gen-6.. HCI , A620 BuLi 9 Q g ( 57%) -——’BBr 93.9 (70%) wag-.6 45 TiCI. , Zn , THF , g (81%) @359 9 Figure 3. Synthesis of [3(b, b) b.1. 1]triptycene 20 via 2, 3; 6,‘Pnaphthadiyne equivalent 38. So far we have briefly described the history from triptycene to extended triptycenes (iptycenes). The basic 11 concepts are summarized as follows:(a) cycloaddtion of an aryne (i.e. 4, 13) to an acene (i.e. anthracene, tetracene, pentacene) directly constructs the triptycene framework. (b) di-aryne equivalents (i.e. 31, 38, 40) can be used to build up iptycenes quickly. The main part of this thesis will discuss the application of these concepts to the synthesis of higher iptycenes. C. Reasons for The Synthesis of Iptycenes. As we have pointed out, triptycene can be considered as the first member of a large series of compounds, namely "iptycenes". For example, fusion of a single 9,10-anthradiyl moiety 46 to triptycene 1 at an a or b bond can give pentiptycene 22 or 24, respectively. Fusion of two 9,10-anthradiy1 moieties at b and b' will give heptiptycene 27, etc. Elaboration of 1 with one to six 9,10-anthradiy1 moieties leads to 24 possible different iptycenes.19 Only a 19'20 and the remainder few of these iptycenes are known, provide a synthetic challenge. Although this thesis does not deal with these particular iptycenes, the general synthetic strategies for attaining such compounds will be discussed. 12 Besides the synthetic challenge, iptycenes possess a number of interesting properties which make their synthesis worthwhile. One of these properties is high melting points and high thermal stability. For instance, the melting points of triphenylmethane, triptycene 1, pentiptycene 24, and heptiptycene 27 increase from 94'to 256'to 483 to >525'. The factors which lead to these unusually high melting points are not obvious. It is important to examine their x- ray structures, particular the packing patterns.21 Polyiptycenes, like polyphenyls, could be potentially useful heat-resistant materials.22 Another interesting feature of these iptycenes is their molecular cavities, which could be useful in forming host-guest compounds. As previously mentioned, heptiptycene 27 has a U-shape cavity with two parallel arene rings, as shown in an end-on view. The cavity may be used to trap metal ions or small organic molecules. (51 meg 27(end-on view) There are many other interesting structural features of iptycenes besides high melting points, high thermal stability, and possibilities as hosts in molecular 13 complexes. For example, spectral properties involving ring- ring interactions,11 novel organometallic complexes, novel photochemistry and unusual semi-conductor design. This thesis will deal mainly with the synthesis of parent iptycenes. First, the synthesis of some useful synthons, including both dienophiles and dienes will be described. Then, it will be shown how these synthons can be applied to .improved syntheses of 20, itself a useful iptycene synthon, and to higher iptycenes. Like 20, [3(b,b)b.1.3(b,b)b]triptycene 109 and [3(b,b)b.3(b,b)b.3(b,b)b]triptycene 110 are both potential synthons for the synthesis of higher iptycenes‘ or polyiptycenes. We shall discuss the attemped synthesis of these synthons via heptacene equivalents in the second part of this thesis. The synthesis of linear acenes (i.e. tetracene and pentacene, which are difficult to obtain by literature methods) via cycloaddition of epoxides (7, 38, 50) and benzocyclobutene will be presented, to demonstrate the versatility of these epoxides. In addition, the use of 5,14-dihydropentacene as a diene in cycloadditions with epoxides 50 and 38, which leads to the synthesis of potential synthons 109 and [3(b,b)b.1.2b]triptycene 143, will also be described. Finally, we shall describe the bis-cycloadduct of epoxide 40 and tetraphenylcyclopentadienone 153, which is a useful synthetic equivalent of furano[3,4-f]benzo[c]furan 133. .Its synthesis and application to the preparation of linear polycyclic arenes will be presented. 14 RESULTS AND DISCUSSION A. USeful Synthons. Triptycenes are usually prepared by aryne addition to an anthracene. Cycloaddition will also be important to build up higher iptycenes. A general approach to the construction of iptycenes is shown in Fig. 4. ” + 03 BuLi —>- {. (“1.3) {n + “} 514-1» ,, + at Aflfli» g (ea-5) } {@@@ 9,2 Figure 4. General construction of the iptycene framework. 15 First, an aryne generated from a 1,2-dibromoarene and trapped with an anthracene moiety will give directly the iptycene framework (eq.1). Second, aryne addition to a his— methylene moiety, followed by dehydrogenation will then give one additional fused ring in the resulting iptycene system (eq.2). Third, a furan adduct can be generated as in eq.3 and used as an aryne equivalent (epoxide) which, on reaction with an anthracene moiety followed by dehydration gives another route to fused-ring iptycenes (eq.4). Finally, cycloaddition between this aryne equivalent and a bis- methylene moiety, followed by dehydration and dehydrogenation, provides another method for constructing the iptycene backbone, now with three fused rings (eq.5). Rather than tackle each particular iptycene as a unique synthetic challenge, it is useful to have available a number of building blocks which can be employed in various. sequences to construct certain ring systems. Some synthons that we have found useful are listed in Table 1. They are either aryne or di-aryne equivalents. Dienes such as anthracene 5, [3(b,b)b.1.1]triptycene 20, and the bis- methylene compound 52 are also needed as building blocks. @ ow 6,, 5 20 52 16 Table 1. Synthons Useful as Aryne or Di-aryne Equivalents. :13}: :6: :37: 2'»— w :u no w on 17 24 which is useful as the 1,2,4,5-Tetrabromobenzene 31, synthetic equivalent of either 4,5-dibromobenzyne 37 or 1,4- benzadiyne 36, is readily prepared in good yield by bromination of commercially available 1,4-dibromobenzene. Various synthons can be derived from 31 (Fig. 5). Treatment 3" 3' 190. BuLi. Q > 3" Br Br toluene a ‘23‘C Br 31 38(709‘) TiCI.,2n. B'.1N.BuLi. (f) THF Br toluene.RT a 49 (85%) 50 (81%) Sr 8' zeq.BuLi. 0 > ”a“ Br Br toluene. -23‘c (ul(syn & anti; 3‘ 70%) Figure 5. Synthesis of various synthons from 1,2,4,5- tetrabromobenzene 31. of 31 with either one or two equivalents of n-butyllithium 14b'18 These reactions as and furan gives synthon 38 or 40. described in the literature, were generally carried out at -23°C. At this temperature most of the tetrabromobenzene precipitated; consequently only small scale reactions could be carried out or else large volumes of solvent were necessary. After some trials, we have developed optimum 18 conditions for these reactions using a minimum amount of solvent so that the reactions can be scaled up to produce ten grams of product(see Experimental Part for details). 2,3-Dibromonaphthalene 49 is a useful 2,3-naphthyne 25 The equivalent. It has been prepared by several methods. best of these involved bromination of the commercially available naphthalene-hexachlorocyclopentadiene bis-Diels- Alder adduct 53 followed by pyrolysis of the bromination product at 220°C.25d The overall yield for the two steps was 46%. However, we found that the pyrolysis step occasionally involved rearrangement of 49 to its isomer 1,3-dibromo- naphthalene 55. The evidence came from the 1 H NMR spectrum, which showed two one-proton singlets at 5 8.13 and 7.94 for the halogenated ring protons, and two two-proton doublets of doublets (AA'BB') at 6 7.73 and 7.50 for the non- halogenated ring protons. The expected product 49 showed, on the other hand, a two-proton singlet at 6 8.15 and two two-proton doublets of doublets at S 7.48 and 7.68 as required by its symmetry. 19 We describe here an alternate route to 49 involving 29 the metal-catalyzed deoxygenation of 38 with TiCl4 and zinc, which proceeds in excellent yield (86%). The 2,3-anthryne equivalent 50 is readily prepared from 49. The literature method25a used phenyllithium, whereas we used n-butyllithium instead with equal effect but a simpler purification. Simple recrystallization gave the desired product in high purity without column chromatography. Butadiene 52, with a 9,10—anthradiyl unit fused to the 2,3 positions, is a useful diene for iptycene synthesis. 26 The literature syntheses of 52 require four steps from 27 anthracene, except for one which requires only two steps. However, the latter did not report experimental details. We describe here the use of 1,4-dichloro-2-butene28’31 56 as a dienophile in the cycloaddition with anthracene. The mixture of cis and trans cycloadducts was dehydrochlorinated 26b using potassium t-butoxide in DMSO. The overall yield for the two steps was 85%. ”ft + CICHrC H=CH-CH2CI _> 5 56 0 KOt-Bu omso CICH 6 ’ > cncuz 5” (cis & trans; 96$) 52 (39%) 20 As we have described above, the basic synthons are now readily available. We shall discuss later how these synthons can be applied to the synthesis of higher iptycenes. B. Exo Selectivity in Endoxide Cycloadditions. In this study, 7-oxabicyclo[2.2.1]hepta-2,5-dienes of the type 48 have been used frequently as dienophiles in cycloadditions with an anthracene moiety, to construct the iptycene framework (see Fig. 4; eq.4). The cycloadduct may have two possible configurations, exo 59 or endo 60. The ab 1:; o~1 n2 60 (endo) Figure 6. Exo and endo adducts of 7-oxabicyclo[2.2.1]- hepta-2,5-dienes 48 with anthracene. endo adduct is thought to be the kinetic product. However, the severe steric crowding and 1r-w-repulsion makes this addition mode highly unfavorable. The thermodynamically favored exo adduct is thus the only product formed. The two isomers can be readily distinguished by their proton NMR 21 30 In the exo isomer, the dihedral angle between Ha spectra. and Hb or Rb and Hc is close to 90° , so that the bridge methine protons Ha and HC show no coupling with the Hb protons.l Thus we should be able to see three "singlet" aliphatic protons in the exo isomer's spectrum. In the endo isomer, the dihedral angle is about 65°, and Jab or ch should be about 4-5 Hz. Exo selectivity is prevalent throughout this study. None of the endo isomer has been found. This selectivity will not be mentioned in most synthetic sequences, but in some cases it is important in assigning structures. C. An Improved Synthesis of [3(b,b)b.1.1]Triptycene (20). Triptycene 20 was previously synthesized by the route shown below.11a The overall yield was only 8.4% from 18 12,13 which itself is difficult to obtain. (24%) A! (0-0), A (39%) 20 18 Since 20 is potentially a very useful synthon for iptycenes, through cycloadditions to the anthracene moiety, we sought a good short route to it. Four methods will be presented, because they illustrate different uses for the various synthons (Fig. 4) and also because two intermediates (44 and 45) in the longest synthesis (route a) can 22 themselves be useful synthons. The syntheses of 20 are schematically outlined in Fig. 7. Route: 3. —————-> b -------- > . 0 ‘ d - ------- D» Figure 7. Schematic syntheses of [3(b,b)b.l.l]triptycene 20 via various synthons. 23 Method A : The first good synthesis of 20 was developed by Hart and Meador18 from 38, using di-aryne equivalent methodology (Fig. 3). Treatment of 38 with anthracene in refluxing xylene gave a single exo adduct 43 in 96% yield. Meador used hydrochloric acid and acetic anhydride as the dehydrating reagent to remove the oxygen bridge, but it was found that this reaction was frequently not reproducible. After several different conditions were tried, we found that perchloric acid in ethanol was an effective dehydrating reagent, giving 44 in 65% yield. HClOnEtOH» 6‘ (65%) 3 99 Q ‘3 44 The last ring was added by cycloaddition of the correspounding aryne to furan followed by deoxygenation of the resulting adduct 45 with low valent titanium. The overall (yield of 20 in four steps from 38 was 35%. In this way multi-gram amounts of 20 can be obtained quite readily after reaction condition for each step in the sequence were optimized. Although this route to 20 is somewhat long, two potentially- useful iptycene synthons 44 and 45 are generated. Their use in the synthesis of higher iptycenes will be demonstrated later (vide infra). 24 Method B : This route uses 2,3-naphthyne equivalent 49 as the synthon.19'31 Treatment of 2,3-dibromonaphthalene 49 with one equivalent of n-butyllithium at room temperature generates 2,3-naphthyne 13, which is trapped with diene 52 in situ (application of Fig. 4: eq.2). The dihydroadduct 62 was then dehydrogenated using 10% Pd/C in refluxing xylene to give 20. The overall yield for the two-step sequence was 78%. at” + Bu Li . Toluene 8r R31 (80%) 49 @ ‘ Pd/c , xylene > 20 (98%) of)“ The structure of the intermediate 62 was confirmed by its spectra. The 1H NMR spectrum showed a two—proton singlet at 6 4.92 for the bridgehead protons and a four- proton singlet at 6 3.82 for the allylic protons. Also present was a two-proton singlet at 5 7.58 for the uncoupled naphthalene protons, and a two-proton doublet of doublets at 5 7.70 for the coupled naphthalene protons, as well as a doublet of doublets at 6 6.96(4H) and a multiplet at 5 7.34 (6H) for the remaining aryl protons. The mass spectrum had . a molecular ion peak at m/g 356. 25 Method C : This route starts with the three-ring precursor 50, a 2,3-anthryne equivalent (application of Fig. 4; eq.4). Cycloaddition of 50 to anthracene in refluxing xylene gave exo adduct 63 in 93% yield. Acid dehydration using hydrochloric acid and acetic anhydride gave 20 in 67% yield. The overall yield for the two-step sequence was 62%. 96“ + 666 €53?" 5o 5 HC' , A620 (67%) The structure of adduct 63 was confirmed by its_ 1H NMR spectrum showed a two-proton singlet at spectra. The 6 2.36 for the endo protons, a two-proton singlet at 8 5.08 for the bridgehead protons adjacent to the oxygen , and a two-proton singlet at 5 4.49 for the remaining bridgehead protons. The aromatic region contained a naphthalene moiety which appeared as follows : 6 7.72(dd,2H), 7.52(s,2H), 7.40 (dd,2H). In addition, there were four two-proton doublets of doublets at 6 7.02, 7.17, 7.24 and 7.33 for the remaining 13C NMR spectrum of 63 showed only aryl protons. The fourteeen peaks (three aliphatic carbons at 6 47.52, 49.21, 81.23 and eleven aromatic carbons) as required by symmetry. The mass spectrum showed a molecular ion peak at m/e 372. 26 Method D : This route starts from another 2,3- naphthyne equivalent, 7, which was readily available from 33 the reaction of benzyne with furan. Cycloaddition of 7 to 52 gave adduct 64 in 89% yield. The Stereochemistry of 64 was not determined, but probably was exo. The 1H NMR HCl . Aug. Ho g Pd/C : mm" , (56%) gaia @ Hch spectrum of 64 showed two two-proton singlets at 6 4.78 and 4.92 for the bridgehead protons, and three sets of two- proton doublets of doublets at 6 1.87, 2.20 and 2.82 (ch=14 Hz; Jab=7 Hz; Jac=5 Hz) for the Ha' Hb and Hc protons. The remaining aryl protons appeared as a four-proton multiplet at 6 6.85-6.91 and an eight-proton multiplet at 6 7.05-7.23. 13C NMR spectrum had thirteen peaks (four aliphatic The carbons at 6 30.47, 42.01, 55.77, 84.98 and nine aromatic carbons) as required by symmetry. The mass spectrum showed a molecular ion peak at m/g 374. I The dehydration of 64 with acid (56%) was accompanied by double-bond isomerization to give vinylnaphthalene 65, as 27 indicated by loss of the symmetry expected in the 1H NMR spectrum. For example, the spectrum contained a triplet at 5 2.32 for the allylic protons (Ha) and two doublets of doublets at 6 2.72 and 2.96 for the benzylic protons (Hb and HG). Also, the bridgehead protons appeared as two singlets at 6 4.32 and 4.87, and there was a vinyl proton (Hd) at 6 6.55. The remianing aromatic proton signals were also consistent with a structure in which the double bond had moved into conjunction with the naphthalene moiety. The mass spectrum had a molecular ion peak at m/e 356. Compound 65 was dehydrogenated to 20 in 95% yield by refluxing with 10% Pd/C in mesitylene for 3 days. The overall yield for the three-step sequence from 7 and 52 was 47% (application of Fig. 4; eq.5). All four methods presented here are improvements over the literature method.11a The particular choice will depend on which synthons are available, and whether or not additional functionality (for example, bridgehead substituents) are desired in the final product. D. Cycloadditions of [3(b,b)b.1.1]Triptycene (20) with.TCNE (66), DMAD (67) and 1m (68). The possible use of 20 as a synthon for higher iptycenes was first tested with simple dienophiles such as tetracyanoethylene (TCNE, 66), dimethyl acetylene- dicarboxylate (DMAD, 67), and maleic anhydride (MA, 68). All three reactions gave a cycloadduct quite readily in high yields. 28 NC) CN cm, N. < CN (98%) as 20 + CH3COz-CEC-COZCH3 3%» 67‘ a (96%) 68 The structures of the cycloadducts (69, 70, and 71) were confirmed by their spectra. The most characteristic feature of their 1H NMR spectrum is the disappearance of protons due to the anthracene moiety and the formation of additional bridgehead protons. Two sets of bridgehead protons and the uncoupled benzenoid protons of the central ring are the most obvious features of the spectra. For example, singlet peaks appear at 6 5.69, 5.75 and 7.82 for 69; at 6 5.31, 5.35 and 7.42 for 70, and at 6 4.71, 5.40 and 7.39 for 71. The reactivity of the anthracene moiety in 20 toward dienophiles in the Diels-Alder reaction is somewhat retarded compared with that of anthracene itself, probably due to additional steric crowding caused by the 9,10-anthradiyl moiety. 29 E. Synthesis of a series of [nb.1.1b .1.1]Pentiptycenes via [3(b,b)b.1.l]Triptycene. With diene 20 now readily available by several good methods (vide supra), it was possible to use this synthon with the various dienophiles shown in Table 1 to synthesize a series of pentiptycenes, as briefly outlined in Fig. 8. 1. Improved Synthesis of [1.1.1b.1.1]Pentiptycene (5,14[1',2']:7,12[1',2']-Dibenzeno—5,7,12,14-tetrahydro— pentacene) (24) . The first example in Fig. 8 demonstrated here was an improved synthesis of 24. The previous one-step synthesis of 24 from 31, anthracene and n-butyllithium proceeded in 94% yield based on the consumed anthracene. In fact, however, the practical yield is only 26% based on 31.14a There are some technical difficulties with this method, and also a substantial amount of anthracene remains which must be separated from the desire 24 by chromatography and/or sublimation. Hence, a better route seemed desirable. Since we can now make 20 readily by good methods, 24 can be prepared in one step from the reaction of 20 with benzyne (via benzenediazonium-Z-carboxylate hydrochloride). The yield was 65%.19 Q @I g Q ‘ ’ 0%.} @679 (65%) G) 24 o \ 0 ("’9 0‘ 31% 5333.29 9"9 8 as 9 a” @ Figure 8. Schematic syntheses of [nb.1.1b.1.1]- pentiptycenes via [3(b,b)b.1.1]triptycene 20. 31 2. [2b.1.1b .1.1]Pentiptycene (5,16[1',2']:7,14[1',2']- Dibenzeno-5,7,14,16-tetrahydrohexacene)(76) The availablity of synthons epoxide 48 (i.e. 7, 38, 50) and 20 allowed us to construct pentiptycenes with an "outer" fused-ring moiety (see general approach in Fig. 4, eq.4). Cycloaddition of 7 and 20 in refluxing xylene for 2 days gave exo adduct 72 in 91% yield. Four possible isomers may be formed ( two exo and two endo ; Fig. 9 ) in this xylene (91%) endo-74 ' endo- 75 ,2 He: , Ac20_’ \9.’ (53%) b Figure 9. Synthesis of [2b.1.1 .1.1]pentiptycene 76. 32 reaction. However, only one isomer was actually observed. Structures 74 and 75 can be ruled out easily by looking at the severe steric crowding and lack of observed coupling between the endo protons and the bridgehead protons (see discussion in exo selectivity). The stereochemistry of the adduct was not determined, but probably was 72, which is less crowded than 73. The 1 H NMR of 72 showed four two-proton singlets at 6 1.97, 4.22, 4.80, and 5.30 for the bridgehead protons, and a two-proton singlet at 5 7.25 for the uncoupled benzenoid ring protons. The remaining aryl protons appeared as six sets of two-proton and one set of four-proton doublets of doublets at 5 6.88, 6.92, 6.97, 7.18, 7.24, 7.33 and 7.06. 13C NMR spectrum gave seventeen peaks (two peaks were The missing due to quarternary carbons or _overlapped signals) with four aliphatic carbons at 6 47.25, 48.85,. 53.97, and 81.13. The mass spectrum showed a molecular ion peak at m/g 498. Adduct 72 was dehydrated using hydrochloric acid and acetic anhydride to give the desired pentiptycene 76 in 53% yield. The structure of 76 was assigned from its spectra. The 1 H NMR spectrum consisted of two two-proton singlets at 8 5.31 and 5.41 for the bridgehead protons. The aromatic protons appeared as two two-proton singlets at 6 7.48 and 7.68 for the uncoupled benzenoid ring and naphthalene ring protons, a two-proton doublet of doublets at 6 7.63 for the coupled naphthalene peri protons, and two sets of multiplets at 6 6.83-6.95 and 7.25-7.34 for the remaining aryl protons. 33 The 13C NMR spectrum had nineteen peaks (two aliphatic carbons at 6 53.59 and 53.96 as well as seventeen aromatic carbons), as required by the symmetry. The mass spectrum showed a molecular ion peak at m/e 480. The overall yield for the two-step synthesis of 76 from the readily available 7 and 20 was 48%. 3. 5,16[1',2']:7,14[1",2"]-Dibenzeno-10,11-dibromo- 5,7,14,16-tetrahydrohexacene (78). The successful synthesis of 76 led the way to other fused-ring pentiptycenes. Thus, by replacement of synthon 7 with 38 in the synthetic scheme (Fig. 9) one can obtain the target compound 78. Reflux of 38 and 20 in xylene for 3 days again yielded only a single isomer, 77, in 89% yield. The adduct was dehydrated using sulfuric acid and acetic acid to give pentiptycene 78 (61%). The overall yield for the two-steps was 54%. :uflene (89%) (61%) 34 The structures of 77 and 78 were confirmed by their spectra, which were similar to those of 72 and 76. The 1H NMR spectrum of a series of pentiptycenes is listed in Table 2. The 13C NMR spectrum of 78 showed seventeen peaks (two peaks were missing due to quarternary carbons or overlapped signals) with two aliphatic carbons at 6 53.39 and 53.90. The mass spectrum showed a strong molecular ion peak at m/e 638. 4. [3(b,b)b.1.1b .1.1]Pentiptycene (5,18[1'.2']:7,16[1',2']- Dibenzeno-5,7,16,18-tetrahydroheptacene)(81) We have described the synthesis of naphthalene fused- ring pentiptycenes, 76 and 78. The anthracene analog can be similarly prepared. Heating 50 and 20 in xylene for 4 days afforded two regioisomeric adducts, 79 and 80, in 91% yield and approximately 59:41 ratio by NMR. 35 The structures of the adducts were assigned based on the 1H NMR spectrum. The major isomer had a spectrum which consisted of four two-proton singlets at 6 2.12, 4.28, 4.93 and 5.31 for the bridgehead protons, and two two-proton singlets at 6 7.25 and 7.43 for the' uncoupled benzene and naphthalene ring protons. The minor isomer contained corresponding peaks at 6 2.29, 4.36, 4.99, 5.35, and 7.33 and 7.45. The remaining aromatic peaks were too complex to assign. The mixture was not separated but dehydrated directly using perchloric acid to give pentiptycene 81 in 41% yield. The structure of 81 was also confirmed by its 1H NMR spectrum. The protons of the anthracene moiety were apparent as two two-proton singlets at 6 8.18 and 7.80 and two two-proton doublets of doublets at 6 7.89 and 7.36. In addition, there were two two-proton singlets at 6 5.33 and 5.44 for the bridgehead protons, a singlet at 6 7.51 for the central benzenoid ring protons, and remaining peaks correspounding to the twelve aryl protons (see Table 2). The mass spectrum showed a molecular ion peak at m/g 530 as the base peak. The UV spectrum possessed a set of bands typical of an anthracene, with the longest wavelength absorption at 374 nm. 5. Synthesis of 7,12[1',2']-Benzeno-15,16-dimethylene-5,14- ethano-5,7,12,14-tetrahydropentacene (83). So far we have successfully demonstrated a general route to the synthesis of fused-ring pentiptycenes by 36 b Table 2. 1H NMR Spectra of [nb.1.1 .1.1]pentiptycenes. positiona remaining aryl compound 1 2 3 4 5 6 protons 24 5.30 5.30 7.43 7.28b 6.92b 88 5.29 5.33 7.40 7.58 6.87-6.92(6H): 7.22-7.33(6H) C 76 5.31 5.41 7.48 7.68 7.63b 6.83-6.9S(6H)C 7.25-7.34(8H) 78 5.34 5.40 7.49 7.50 7.88 6.86-6.99(6H): 7.25-7.35(6H) 81 5.33 5.44 7.51 7.80 8.18 7.89b (6.86,6.91,6.9§)b 7.27-7.38(8H) 86 5.32 5.42 7.49 7.77 8.20 8.06 (6.85,6.91,6.98 7.25,7.29,7.35$b 8. Position 1 to 6 refer a two-proton singlets except for b superscript. b. A two—proton doublet of doublets. c. Multiplet with assigned protons in parentheses. 24(X=H) 78 (X=H) 88(X=CO,CH,) 78 (X=Br) 37 employing the cycloaddition of epoxides (i.e. 7, 38, 50) and synthon 20, followed by dehydration of the resulting adducts (application of Fig. 4; eq.4). Another method to achieve the goal is to fuse the ring by cycloaddition between the epoxide and a bis-methylene compound (see general approach in Fig. 4; eq.5). Synthesis of the necessary bis-methylene moiety from anthracene has been described earlier. Similarly, the higher analogue 83 can be prepared from 20. Reaction of 20 6 o 0 ‘@ Cloth-curmuzcu 4fl+ ”$4 (66%) CICH 1‘SHCJZ:’ (”CH {:5 20 56 82 (cis & trans) K0t-8u.07())so+ 96.6.4@ (83%) 7 <:) I! with 1,4-dich1oro-2-butene (sealed tube, 1950 , 3 days), followed by base-catalyzed elimination gave the bis- methylene compound 83 in 55 % overall yield. The structure of 83 was clear from its 1H NMR spectrum. It showed two- proton singlets at 6 5.20 and 5.34 for the bridgehead protons, and peaks at 6 4.75 and 5.05 for the vinyl protons. The aromatic region contained a two-proton singlet at 6 7.36 for the central benzenoid ring protons and six sets of two- proton doublets of doublets ( 6.89, 6.96, 7.03, 7.22, 7.28, 38 13 7.33) for the remaining aryl protons. The C NMR spectrum gave) sixteen peaks as required by the symmetry. The mass spectrum showed a strong molecular ion peak at m/g 406. The use of diene 83 in cycloadditions to synthesize fused-ring or functionalized pentiptycenes will be discussed below. 6. Synthesis of 5,18[1',2']:7,16[1',2']-Dibenzeno-11,12- dibromo-5,7,16,18-tetrahydroheptacene (86). Heating 83 and 38 in refluxing xylene for 60 h gave adduct 84 in 81 % yield. The stereochemistry of 84 was not determined, but probably was exo. Dehydration of 84 using perchloric acid proceeded with double-bond isomerization (a similar phenomenon has been observed; see the synthesis of 20, method D: vide supra) to give vinyl naphthalene 85 in 57 % yield. Finally, compound 85 was dehydrogenated to dibromoanthracene 86 (94 %) by refluxing with Pd/C in mesitylene for 4 days. 39 The 1H NMR spectrum of 86 showed two two-proton singlets at 6 5.32 and 5.42 for the bridgehead protons. The anthracene moiety was easily apparent as three two-proton singlets at 6 8.20, 8.06 and 7.77. In addition, a two- proton singlet for the uncoupled benzenoid ring protons and six sets of two-proton doublets of doublets for the remaining aryl protons were present (see Table 2). The 13C NMR spectrum of 86 showed sixteen peaks (five peaks were missing due to quarternary carbons or overlapped signals) with two aliphatic carbons at 6 53.47 and 54.03 . The mass spectrum65 showed a molecular ion at m/g 688 as base peak. 7. Synthesis of Dimethyl 5,14[1',2']:7,12[1',2']-dibenzeno- 5,7,12,l4-tetrahydropentacene-2,3-dicarboxylate (88). The diene 83 can also be used to synthesize functionalized pentiptycenes. For example, ring fusion between 83 and 67 gave 88 directly in 87 % yield. The ooze H, :3 4’ g; A’ .> (”ifiyc “II 8 b02C H3 ( 7%) CHJW 67 40 intermediate 87 was automatically dehydrogenated under refluxing xylene conditions. The structure of 88 was confirmed by its spectra. The 1H NMR spectrum (Table 2) showed a six-proton singlet at 6 3.80 for the methyl protons, and two two-proton singlets at 6 5.29 and 5.33 for the bridgehead protons. The aromatic region consisted of two two-proton singlets at 6 7.40 and 7.58 for the uncoupled benzenoid ring protons, as well as two sets of six-proton doublets of doublets for the remaining aryl protons. The 13C NMR spectrum gave only sixteen peaks (three peaks were missing due to either quarternary carbons or overlapped signals) with aliphatic carbons at 6 52.38, 53.53 and 53.88. The mass spectrum showed a strong molecular ion peak at m/e 546. As discussed in this section, one can see clearly the versatility of 20 as a synthon in the synthesis of a series of pentiptycenes (Fig. 8). Among them, compounds 78, 81 and 86 are useful potential synthons for even higher iptycenes. The dibromo moiety in 78 and 86 is an aryne equivalent. The anthracene moiety in 81 and 86, on the other hand, can be utilized as diene. F. Synthesis of [1.1.3(b,b)b.1.1b .1.1]Heptiptycene (5,22[1',2']:7,20[1",2"]:11,16[1"',2"']-Tribezeno- 5,7,11,16,20,22-hexahydrononacene)(90). As we have mentioned earlier, compound 45 might serve as a useful synthon. The double bond in 45 is an 41 effective dienophile. Thus, cycloaddition of 45 and 20, followed by dehydration of the adduct gave heptiptycene 90 in good yield. In this case, mainly one cycloadduct, lHCflCh EtOH (70%) thought to be 89, was formed in 88 % yield. The 1H NMR spectrum of 89 showed five sets of two-proton singlets at 6 1.85, 4.06, 4.75, 5.30 and 5.47 for the bridgehead protons. In addition, there were two-proton singlets at 6 7.67 and 7.30 for the naphthalene moiety, and at,6 7.21 for the uncoupled benzenoid ring protons. The remaining aryl protons appeared as follows : 6 6.86—7.07 (m,12H), 7.32- 7.41(m,8H). Dehydration of the adduct 89 using perchloric acid gave 90 in 70 % yield. The structure of 90 was confirmed by its spectra. The 1H NMR spectrum showed three two-proton singlets at 6 5.31, 5.39 and 5.47 for the bridgehead protons. The anthracene moiety was apparent as three two- proton singlets at 6 8.01, 7.78 and 7.72. In addition, 42 there was a two-proton singlet for the uncoupled benzenoid ring protons, and the remaining aryl protons (twenty) appeared as six sets of two-proton doublets of doublets at 6 6.83, 6.90, 6.94, 7.24, 7.28 and 7.33, and two four-proton multiplets at 6 7.00 and 7.40. The 13 C NMR spectrum gave twenty-one peaks (seven peaks were missing due to either quarternary carbons or overlapped signals) with three aliphatic carbons at 6 53.44, 53.59 and 53.95. The mass spectrum showed a molecular ion at m/g 706 as the base peak. The UV spectrum of 90 possessed a set of bands typical of an anthracene, with the longest wavelength at 371 nm. Cycloaddition of DMAD to the anthracene moiety of 90 gave exclusively one regioisomer. If dienophile approaches ozcn3 43 from face "a" of the anthracene moiety(less hindered), adduct 91 will be obtained. On the other hand, if dienophile attacks from the more hindered face "b" (an additional 9,10-anthradiyl moiety is on this face ), one will get adduct 92. The product is thought to be 91. The‘ unusual upfield chemical shift of the bridgehead and uncoupled benzenoid ring protons support structure 91, even though this structure may be more hindered than 92, which has a zig-zag extended geometry. The 1H NMR spectrum of the adduct showed a six-proton singlet at 6 3.65 for the methyl protons, and three singlets at 6 5.14, 5.18 and 5.20 (ratio 2:4:2) for the bridgehead protons. The aromatic region contained two singlets at 6 7.27 and 7.28 (ratio 4:2) for the uncoupled benzenoid ring protons, and the remaining aryl protons appeared as follows: 6 6.78(dd,4H), 6.85(dd,4H), 6.91(dd,2H), 7.15-7.26(m,10H). The 13 C NMR spectrum gave only twenty-two peaks (nine peaks were missing due to either quarternary carbons or overlapped signals) with five aliphatic carbons at 6 52.20, 52.21, 52.36, 52.81 and '52.82. The mass spectrum showed a molecular ion peak at m/e 848. Note that structure 91 completes five of the six sides in hexagonal cycloiptycene 93 (head-on view). Its enclosed cavity could be useful in forming host-guest compounds. The benzyne adduct of 90, such as 94 or 95 is an attractive synthetic target. However, an attempt to synthesize these compounds was not successful (benzyne generated from benzenediazonium-Z-carboxylate hydrochloride). Further 44 M i investigation on different conditions or with other benzyne precursors seems desirable. b D G. Synthesis of [1.1.1 .1.3(b,b)b.1.1 .1.1]Noniptycene (98 and 103). Bis-epoxide 40, a synthetic equivalent of 2,336,7- anthradiyne is a powerful synthon for constructing higher iptycenes ( see Fig. 2, p.9). Here we illustrate another synthesis of noniptycenes, to show the versatility of epoxide 40. If the reaction scheme in Fig. 2 is extended by replacing anthracene with triptycene 20, noniptycenes 98 and 103 can be readily obtained. (1) Syn-noniptycene (98). Heating syn-40 and two equivalents of 20 in a sealed tube (xylene as solvent) at 180°C for 3 days afforded a mixture of regioisomers 96 and 97 (NMR ratio 1:1) in 70 % yield. The stereochemistry of bis-adducts 96 and 97 was assigned as exo, a thermo- dynamically-controlled product (the endo adducts would be highly hindered sterically). singlets for the bridgehead 1 protons in the H NMR spectrum supported the exo structures (see discussion of exo selectivity, vide supra). 45 S .. Y? 40 A -———> 2 20 (70%) HC|O4 , EtOH (46%) The 1H NMR spectrum of the adducts showed clearly two sets of bridgehead. One set appeared at 6-1.85, 4.19, 4.71, and 5.23 .(area ratio 4:4:4:4). Another set of peaks corresponding to the other isomer appeared as 6 1.99, 4.23, 4.74 and 5.28 (area ratio 4:4:4:4). The remaining aryl peaks were too complicated to assign to individual isomers; they appeared as follows : 6 6.76(s), 6.86-6.94(m), 6.95(s), 7.02-7.08(m), 7.12-7.21(m), 7.23(s), 7.25-7.33(m). The mixture of the adducts was not separated but was dehydrated directly using perchloric acid to give the syn- noniptycene 98 in 46 % yield. The structure of 98 was confirmed by its spectra. The 1H NMR spectrum showed two four-proton singlets at 6 5.290 and 5.361 for the bridgehead protons, and a four-proton singlet at 6 7.449 for the uncoupled benzenoid ring protons. In addition, the anthracene moiety was apparent as singlets at 6 7.946 and 7.688, area ratio 2:4. The remaining aryl peaks appeared as 46 follows : 6 6.802-6.835(dd,4H), 6.878-6.951(m,8H), 7.212- 7.328(m,12H). The 13C NMR spectrum showed fourteen peaks (four peaks were missing due to either quarternary carbons or overlapped signals) with two aliphatic carbons at 6 53.502 and 54.006. The UV spectrum of 98 possesed a set of bands typical of an anthracene, with the longest wavelength absorption at 372 nm. The mass spectrum35 showed a strong molecular ion peak at m/g 882. If benzyne were to add to 98 from the bottom (face a) of the anthracene moiety, one should obtain undecaiptycene 99 (cyclic form). On the other hand, if benzyne approaches a ‘ —’ m . 89 100 from the top face b, then undecaiptycene 100 (zig-zag form) will be obtained. However, attempted cycloaddition of benzyne (generated from benzenediazonium-2-carboxylateV hydrochloride) to the anthracene moiety of 98 was not successful; the reaction gave mainly recovered starting material. 47 (2) Anti-noniptycene (103). The anti-noniptycene 103 was syntheSized in a manner similar to 98, by cycloaddition of anti-40 to two equivalents of 20, followed by dehydration of the mixture of the adducts (101 and 102, NMR ratio 1:1) as shown in the equation: Helo, , EtOl-l 43% The 1H NMR spectrum of the adducts also showed clearly two sets of bridgehead protons. One set appeared at 6 1.78, 4.10, 4.62 and 5.30 (area ratio 4:4:4:4) and the other at 6 2.02, 4.23, 4.73 and 5.26. The remaining aryl peaks were too complicated to assign; they appeared as follows : 6 6.77(s), 6.82-6.93(m), 6.98-7.01(m), 7.06-7.10(m), 7.18(s), 7.19-7.35(m). 48 The mixture of adducts was dehydrated using perchloric acid to give 103 in 43 % yield. The spectra of 103 were very similar to those of 98. The 1H NMR spectrum of 103 showed two four-proton singlets at 6 5.295 and 5.365 for the bridgehead protons, and a four-proton singlet at 6 7.452 for the uncoupled benzenoid ring protons. In addition, the anthracene moiety was apparent as singlets at 6 7.947 and 7.689, area ratio 2:4. The remaining aryl peaks appeared as follows: 6 6.802-6.836(dd,4H), 6.879-6.952 (m,8H), 7.213- 7.331(m,12H). The 13C NMR spectrum showed sixteen peaks (two peaks were missing) with two aliphatic carbons at 6 53.442 and 53.959. The UV spectrum of 103 possessed bands similar to those of 98, with the longest wavelength absorption at 372 nm. The mass spectrum35 gave a strong molecular ion peak at m/e 882. Benzyne addition to the anthracene moiety of compound. 103 should give only one adduct 104. The cycloaddition was 104 attempted (benzyne generated from o-benzenediazonium- carboxylate hydrochloride); however, no adduct was 49 successfully isolated. As we have discussed above, one can see clearly the versatility of bis-epoxide 40 as a powerful synthon for higher iptycenes. In only two steps, reaction of 40 and 20, can readily extend triptycenes(three planes) to noniptycenes(nine planes). We hope that further careful 53 reinvestigation of the benzyne addition to the noniptycenes 98 and 103 will furnish the novel iptycenes 99, 100 and 104. H. Synthesis of [4(b,b,b)b.1.1]Triptycene (108). Triptycenes containing naphthalene or anthracene fused ring have been described earlier. The tetracene anolog 108, however, is not known in the literature. Here we describe its synthesis via three-ring precursor 50 and diene 52. The A 63 5° ’ i2 (89%) ’ @Qafi'69 105 HCLAqO (42%) 107 Pd/C ’ (92%) 50 thermal cycloaddition gave a single adduct 105 (89 %). Dehydration using hydrochloric acid in acetic anhydride afforded a mixture of 106 and its double-bond isomer 107 (42 %), which were then dehydrogenated to give the desired tetracene 108. The structure of 108 was confirmed by its spectra. The 1 H NMR spectrum contained a two-proton singlet at 6 5.53 for the bridgehead protons, and two four-proton doublets of doublets at 6 7.07 and 7.46 for the benzenoid ring protons. In addition, the tetracene moiety appeared as follows : 6 8.56(s,2H), 8.46(s,2H), 7.45(dd,2H), 7.86(s,2H), 7.35 (dd,2H). The 13C NMR spectrum showed twelve peaks (one peak was missing) with the aliphatic carbons at 6 53.52. The mass spectrum had a molecular ion peak at m/e 404. The UV spectrum of 108 possessed a set of bands typical of a tetracene, with longest wavelength absorption at 469 nm. I. Conclusions. Iptycenes form a very large class of compounds with rigid well-defined geometries based on elaboration of its simplest member, triptycene. The compounds have novel structures for studying various phenomena in chemistry, such as charge transfer, restricted rotation, thermal stability, host-guest phenomena, factors which contribute to high melting points and many others. In this part of the thesis, we have described a general approach to the iptycene framework ( Fig. 4 ) via seven important synthons (7, 31, 38, 40, 49, 50, 52) and 51 illustrated their utility in improved syntheses of 20 (four routes). We have also demonstrated the versatility of 20 as a synthon in the preparation of some higher iptycenes, including pentiptycenes 24, 76, 78, 81, 86 and 88, heptiptycenes 27 and 89, and noniptycenes 98 and 103. The syntheses we have discussed were limited mainly to the unsubstituted carbocyclic framework, but further elaboration, including heterocycles, functional substituents, etc., is clearly possible. The door to iptycene chemistry has been opened. We anticipate that there will be many delights as we explore its domain. 52 Part II. s 's of 'n r Acen s d l i t cene BIQEBIEngL As mentioned earlier, iptycnes are usually prepared via addition of an aryne or aryne equivalent to an acene (i.e. anthracene, tetracene and pentacene). We have demonstrated the utility of synthon 20 in the synthesis of higher iptycenes in part I. Compound 20 contains an anthracene unit in the triptycene framework as a building block. One can imagine that a triptycene with two anthracene moieties (109) or even three anthracene moieties (110) would be a very useful synthon for the synthesis of complex iptycenes or polyiptycenes. A. Attempted Synthesis of [3(b,b)b.1.3(b,b)b]Triptycene (109) and [3(b,b)b.3(b,b)b.3(b,b)b]Triptycene (110) via Heptacene Equivalents 112 and 121. Compounds 109 and 110 can be viewed respectively as cycloadducts of benzyne or 2,3-anthryne to the middle ring of heptacene 111. However, these direct routes have several problems associated with them. First, heptacene is reported to be a very unstable species.36 Second, heptacene has several possible reactive sites for cycloaddition. Although addition to the middle ring might be preferred, 53 cycloaddition to the other rings, particularly the other 'internal' rings, could also be quite facile. Thus, cycloadditions of a dienophile to heptacene could give quite a complicated mixture. As an alternative to heptacene, we chose 5,9,14,18-tetrahydroheptacene 112 as a "heptacene 8008008 oeoooeo Cycloadditions to 112 should occur only at the central anthracene moiety, and dehydrogenation of the resulting dihydroanthracene moieties in the cycloadducts should give the desired products. The seven linearly fused rings needed for 112 were constructed by addition of two equivalents of o-xylylene 115 to the anthracene bis-epoxide 40. Thermal, 37 ring opening of benzocyclobutene 114 generated the 3 reactive diene o-xylylene, 8 which then added to dienophile 40 to give the bisadduct 116 in high yield. @151 “ 7 {<5} W .6 5» 0000639 118 S Ht HD (99 . .. .3”... 4» 0008000 118 a 54 Thus, heating 40 (syn or anti) and two equivalents of 114 in a sealed tube (toluene as solvent) at 190°for 24 h gave bisadduct 116 in 84 or 87 % yield, respectively. The stereochemistry of 116 was not determined unequivocally, but was probably exo (see discussion in part I). For example, the 1H NMR spectrum of syn-bisadduct 1163 had a four-proton singlet at 6 5.06 for the bridgehead protons, an eight-proton broad singlet at 6 7.09 for the "outer" benzenoid ring protons, and a two-proton singlet at 6 7.18 for the central benzenoid ring protons. In addition, there were three sets of four-proton doublets of doublets at 8 1.97, 2.70 and 2.98 for protons Ha' Hb and Ho (Jab: 6 Hz: ch= 14 Hz; Jac= 11 Hz). The small or zero coupling between Ha and the bridgehead protons suggests exo stereochemistry. 13C NMR of 116s showed eight peaks (three aliphatic and The five aromatic carbons) as required by the symmetry. The structure of anti-bisadduct 116a was also 13C) were confirmed by its spectra. Its NMR spectra (In and very similar to those of the syn isomer. Dehydration of 116s using perchloric acid in refluxing ethanol for 20 h gave mainly the mono-dehydrated compound 117 together with a small amount of desired tetrahydro- heptacene 112. The ratio, by NMR, was 4:1. The 1H NMR spectrum of 117 showed a four-proton singlet at 6 4.06 for the Hd protons, a two-proton singlet at 6 5.24 for the bridgehead protons and three sets of two- proton doublets of doublets at 6 2.11, 2.75 and 3.04 for the protons Ha’ Hb and HC respectively. In addition, the 55 aromatic region showed two two-proton doublets of doublets at 6 7.20 and 7.32 for the "left" benzenoid ring protons, two two-proton singlets at 7.57 and 7.71 for the naphthalene ring protons, and a four-proton broad singlet at 6 7.13 for the "right" benzenoid ring protons. Wst “magi” sosss‘ws (.1.? m . sass—s: HCI . Ac 0 12b (5% 116$ _. HCIOLquOH» m, toluene . 15" (70$) The 1 H NMR spectrum of 112 contained an eight-proton singlet at 6 4.12 for the benzylic protons. In addition, the anthracene moiety appeared as singlets at 6 8.29 and 7.89, area ratio 2:4. The remaining aryl protons were two four-proton doublets of doublets at 6 7.20 and 7.33. To further dehydrate 117, 116s was heated with the same reagent but for a longer time (60 h). This unfortu- nately produced a mixture of the desired product 112 and its isomer 113; the ratio by NMR was 1:2. The isomerization of 112 probably proceeded via either a carbocation rearrangement or a thermal hydrogen walk, since isomer 113 is thermodynamically more stable than 112 by about 3.90 Kcal/mole (calculated difference in aromatic energy).51 56 90099.9 6......» 9.99.93 The structure of 113 was determined by its 1H NMR spectrum. It showed two four-proton singlets at 6 4.06 and 4.21 for the benzylic protons. The aromatic region had peaks typical of two naphthalene units, which consisted of three two-proton singlets at 6 7.69, 7.71 and 7.77 for the uncoupled naphthalenoid ring protons and a two-proton doublet of doublets at 6 7.78 for the coupled peri protons. The remaining six aryl protons appeared as a multiplet at 6 7.15-7.42. The mass spectrum of a mixture of 112 and 113 gave a correct molecular ion peak at m/g 382. Changes in the dehydrating reagents (for example, using hydrochloric acid in acetic anhydride, or perchloric acid in a mixture of methanol and toluene) gave similar results, as did dehydration of the anti-bisadduct 116a. The formation of thermodynamically favored isomer 11345 in the dehydration step made this approach fruitless, because separation of 112 from 113 was difficult due to their structural similarity and to the facile conversion of 112 to 113. Attemped cycloadditions of 112 with several dienophiles (i.e. 6, 50) resulted in further isomerization of 112 to 113. A possible alternative to 112 as a heptacene equivalent was its octahydro analog 121. Its construction would involve a similar strategy, but use diene 119 in place of benzocyclobutene 114. Heating anti-bisepoxide 40a 57 with two equivalents of diene 119 in refluxing dioxane gave bis-cycloadducts 120 in modest (32 %) yield. “iii? + «ass» “’ x——» «sssso The structure of 120 was confirmed by its spectra. The 1H NMR spectrum showed a two-proton singlet at 6 7.04 for the central benzenoid ring protons, a four-proton singlet at 6 4.90 for the bridgehead protons and' multiplets at 6 l.57(8H), l.82(4H), 1.93(8H), 2.12(8H) for the remaining aliphatic protons. The 13C NMR spectrum of 120 gave eight peaks (five aliphatic and three aromatic or vinyl carbons) as required by the symmetry. Dehydration of 120 using various acids gave consistent results which again indicated a mixture of rearranged products. The 1H NMR spectrum was too complicated to analyze. However, it showed several vinyl peaks, suggesting that the double bond had migrated. A naphthalene moiety was also indicated, suggesting that isomerization had occured due to carbocation rearrangements. Although cycloadditions to the dehydration mixture were attemped, no adducts were isolated. 58 Alternatively we thought that reducing the double bonds in 120 prior to dehydration might eliminate the possibility of rearrangement. Hydrogenation of 120 was attemped using several different reagents (i.e. hydrazine, Pd/C, Pt/C). However, the tetra-substituted double bonds were quite resistant to reduction, and the reactions gave mainly recovered starting materials. The isomerizations which accompanied the dehydration of 116 or 120 led us to abandon the synthesis of building blocks 109 and 110 by these routes. An alternative approach to compound 109 starting from 5,14-dihydropentacene will be discussed later in this part of the thesis. B. Synthesis of Tetracenes (15 and 127) and Pentacene (10). Despite the lack of success in the synthesis of heptacene equivalent 112, the successful cycloaddition of 40_ to benzocyclobutene 114 to construct seven linearly fused rings in one step made it worthwhile to explore this reaction further. Tetracene and pentacene are both known compounds, but they are difficult to prepare.51 Here, we digress from the main goals of this research to describe the synthesis of these acenes by exploiting the cycloaddition of 114 to various epoxides (i.e. 7, 38, 50) to build up a linear ring framework. (1) Tetracene Heating equimolar amounts of epoxide 7 and benzocyclobutene 114 in a sealed tube (toluene as solvent) at 185-195°for 24 hour gave cycloadduct 122 in 86 % yield. The structure of 122 was confirmed by it spectra. 59 121.0(0): 1060s 7 (le-l) 114123(X=H) (86%) 38(X= Br) 123 (X=Br)(89%) ’ » X ssos X 125 (X=H) (89%) m (x: Br) (90%) M +13... us (X=H) (look) 127(X= Br) (92$) Figure 10. Synthesis of tetracenes via epoxides 7 and 38 and benzocyclobutene 114. The 1H NMR spectrum showed a two-proton singlet at 6 5.13 for the bridgehead protons, and three sets of two-proton doublets of doublets at 6 2.02, 2.74 and 3.04 for protons Ha' Hb and HC (Jab the aromatic region appeared as two two-proton doublets of =6 Hz; ch=14 Hz; Jac=11 Hz). In addition, doublets at 6 7.14 and 7.24 and a four-proton broad singlet at 6 7.12. The small or zero coupling between Ha and the bridgehead protons suggests exo stereochemistry. The 13C 'NMR spectrum of 122 had nine peaks (three aliphatic and six aromatic carbons) as required by the symmetry. Dehydration of 122 using hydrochloric acid gave the known dihydrotetracene 125 in 89 % yield; this was then quantitatively dehydrogenated to the corresponding tetracene 60 15. The overall yield for the three-step sequence (Fig. 10) was 77 % from 7 and 114, which is superior to the recently reported methods of Gribb1e47b'47C and Rickborn54. Gribble's47b first method involved the cycloaddition of 2,3-naphthyne to 2-methylisoindole followed by deamination of the adduct by m-chloroperbenzoic acid. The yield for the two-step sequence was 44 %. CH, Br ,, \ qs;*Cwafir>@@wsl ”m“ ssss .3» (85%) 15 The second synthesis of 15 reported by Gribble47c involved the cycloaddition of 2,6-naphthadiyne to furan. Subsequent deoxygenation afforded the tetracene in 25 % overall yield from the dibromo ditosylate. [@1324 a...) “@9909” ""’f..’.”.. ¢@@fl——> (78,, @609 (80%) The third method, described by Rickborn,54 used the cycloaddition of 1,3-bis(trimethylsilyl)isobenzofuran to 2,3-naphthyne. Trifluoroacetic acid induced conversion of the adduct to the corresponding anthracene followed by reduction/dehydration of the ketone gave tetracene in 58 % 61 overall yield. SiMe; . SiMe; ss :G C: '22:? a @999 49 SiMe; SIM93 T:;——,——», ssos ::———»'-:" ssss (83%) Our method for the synthesis of tetracene is comparatively simple, proceeds in high yield, and can be scaled up easily. (2) 2,3-Dibromotetracene By employing epoxide 38 in place of 7 in the synthetic sequence, 2,3-dibromotetracene 127 was obtained in a 74 % overall yield (Fig. 10). Intermediates 123, 126 and the dibromotetracene 127 are all previously unknown compounds. The 1H NMR spectrum of 123 showed two two-proton singlets at 6 5.07 and 7.49 for the bridgehead and the uncoupled benzenoid ring protons, and three sets of two- proton doublets of doublets at 6 1.99, 2.70 and 2.98 for protons Ha , Hb and Hc ,and a four-proton broad singlet at 6 7.13 for the remaining aryl protons. The 13 C NMR spectrum contained nine peaks (three aliphatic and six aromatic carbons) as required by the symmetry. The mass spectrum gave a correct molecular ion peak at m/g 406. The 1H NMR spectrum of 126 showed a four-proton singlet at 6 4.06 for the benzylic protons. In addition, the aromatic region consisted of a naphthalene moiety that 62 appeared as two two-proton singlets at 6 7.63 and 8.07 and a benzene moiety as two two-proton doublets of doublets at 6 7.22 and 7.34. The 13C NMR spectrum had nine peaks (one aliphatic carbon plus eight aromatic carbons) as required by the symmetry. The mass spectrum gave a molecular ion peak at m/g 388. Dehydrogenation of 126 using 10 % Pd/C gave 2,3- dibromotetracene 127. Compound 127 is an orange solid (typical tetracene color) which is insoluble in most organic solvents. The insolubility of this material prevented the measurement of its NMR spectrum. The mass spectrum showed a strong molecular ion peak at m/g 386. The UV spectrum of 127 possessed a set of bands typical of a tetracene, with the longest wavelength absorption at 472 nm. (3) Pentacene In a procedure similar to the synthesis of tetracenes 15 and 127, pentacene 10 was synthesized in 64 % overall yield via epoxide 50 and benzocyclobutene 114 as shown below. + @D -.—-—->'.';:, HCI,MeOH: t. u (MAL, 999. P / (‘10:!) ’ @9699 10 63 The structure of adduct 124 was confirmed by its spectra. The 1H NMR spectrum showed a two-proton singlet at 6 5.25 for the bridgehead protons, and three sets of two- proton doublets of doublets at 6 2.12, 2.78 and 3.04 for protons Ha" Hb and Hc. In addition, the aromatic region contained a naphthalene moiety that appeared as follows : 6 7.44(dd,2H),7.62(s,2H),7.79(dd,2H). Finally, the remaining aryl protons appeared as a four-proton broad singlet at 6 7.13. The 13C NMR spectrum had eleven peaks (three aliphatic and eight aromatic carbons) as required by the symmetry. Dehydration of 124 using hydrochloric acid in a mixture of methanol and toluene gave the known 5,14-dihydro- 48 in 74 % yield. The 1H NMR spectrum (not pentacene 128 previously reported) showed a four-proton singlet at 6 4.13 for the benzylic protons, and two two-proton doublets of doublets at 6 7.23 and 7.36 for the benzenoid ring protons. In addition, the anthracene moiety appeared as follows : 6 7.42(dd,2H), 7.92(s,2H), 7.98(dd,2H), 8.36(s,2H). Compound 128 was quantitatively dehydrogenated to pentacene 10, whose spectra (IR, UV, mass) were identical to those of a commercial sample. Pentacene has been synthesized by the fusion of two equivalents of 1,2-dimethylene-cyclohexane to benzoquinone to construct the five ring framework.' Reduction of the ketone followed by dehydrogenation gave a 30 % overall yield for the four-step sequence.55 64 O ZOE . ““6 * Otto \ o 0 O (55$) %72%) > 10 A better route to pentacene was reported by Brucker. 1)CH3CHZSHL__L> ZnCl 2)Raney Ni 56 This synthesis involved the condensation of two equivalents of o-phthalaldehyde with 1,4-cyclohexanedione to give 6,13- pentacenequinone. Reduction of the quinone by aluminum cyclohexoxide afforded pentacene in a 40 % overall yield. 0 CHO KOH. i} ’ 263E... 33.2, 99‘” (51;) @@@@@ Another recent method reported by Rickborn54 described the cycloaddition of 1,3-bis(trimethylsilyl)isobenzofuran to 1,4-benzadiyne generated by the LiTMP-induced 65 dehydrohalogenation of p-dibromobenzene, to give a five-ring cycloadduct. This bisadduct underwent acid-induced conversion to a diketone followed by reduction/dehydration to give pentacene in 39 % overall yield. B SiMe, SiMe; SiMe3 r / 0 .33 + \o 3:21" > some SiMea SiMe; snug, TFA >- diketone 12;HO LAH @@?@@ (1005) Our synthesis of pentacene is comparable to these literature methods. Besides, the 5,14-dihydropentacene 128 obtained in this synthetic sequence is useful, since it can serve as a synthon for two important polyiptycene precursors, 109 and 143 (vide infra). We have demontrated the versatility of epoxides (i.e. 7, 38, 40, 50) as synthons for higher iptycenes in part I. Here again we illustrated the potential usefulness of these epoxides as precursors of linear acenes. Another application of biséepoxide 40, to the synthesis of a synthetic equivalent of furano-[3,4-f]benzo[c]furan 160, will be described in part III of this thesis. 66 C. Isobenzofuran Intermediates Observed from the Mass Spectra of Epoxyarenes (116, 120, 122, 123 and 124). In reviewing the mass spectra of a series of epoxyarenes (i.e. 116, 120, 122, 123 and 124) an interesting phenomenon was observed. Isobenzofuran fragments appeared consistently as base peaks in the mass spectra of these adducts, presumably from a retro Diels—Alder reaction.4o 'H-fi-r .0 114 7 U122 MS D» o + \ 129 fl%&:ru 8 For example, the mass spectrum of 122 gave a base peak at m/g 118 corresponding to structure 129, which could be explained by fi-bond cleavage directed by the oxygen atom in the retro Diels-Alder process. Table 3 summarizes the isobenzofuran fragments observed from mass spectra of epoxy- arenes. Among them, species 133 is especially interesting. Although we have not proved the existence of such a species, the possibility suggested the potential use of a furano- [3,4-f]benzo[c]furan equivalent in synthesis, as will be described in more detail in the third part of this thesis. 67 Table 3. Isobenzofuran Intermediates Observed in the Mass Spectra of Epoxyarenes. isobenzofuran rel. compound fragment m/g intensity 122 129 L / a. 93.6 m0 276 100 123 130 @6906 124 131 / 0.96606 @Oflfio 1. 1168 132 158 100 / @OQGOOG 00(53 0 .5 116a 132 158 100 0.969.’ .0”? \ O 292 21 120 134 158 100 68 D. Synthesis of [3(b,b)b.1.3(b,b)b]Triptycene (109) via 5,14-Dihydropentacene. The heptacene equivalent approach failed to give the desired synthon 109. Here we describe an alternative and successful approach to 109 and to its analogue 143, via 5,14-dihydropentacene 128. Compound 128 was an intermediate in the synthesis of pentacene (vide supra). The anthracene moiety in this molecule is attractive for use as a diene in cycloaddition reactions. Reflux of equimolar amounts of 128 and 50 in xylene for 5 days gave two regioisomeric adducts 135 and 136 (NMR ratio 3:2) in 63 % yield. (48%) Although four products are in principle possible from this cycloaddition, only two were obtained. Their spectra (lack of coupling with bridgehead protons) suggest that both 69 are exo isomers. The 1H NMR spectrum of 135 showed three two-proton singlets at 6 2.35, 4.46 and 5.06 for the bridgehead protons and a four-proton singlet at 6 3.82 for the benzylic protons. In addition, the aromatic region consisted of a two-proton singlet at 6 7.49 and two doublets of doublets at 6 7.72 and 7.39 for the naphthalene moiety, a two-proton singlet at 6 7.18 for the uncoupled benzenoid ring protons, and a two-proton doublet of doublets at 6 7.13 as well as a six-proton multiplet at 6 7.20-7.31 for the remaining aryl protons. The regioisomer 136 had a very similar 1H NMR spectrum except that the benzylic protons showed a quartet-like splitting (AB type),probab1y due to the influence of the nearby oxygen bridge. The mixture of adducts 135 and 136 was dehydrated using hydrochloric acid in acetic anhydride to give a single product 137 (48 %). The structure of 137 was obvious from its 1H NMR spectrum, which showed an anthracene unit and only one set of bridgehead protons. The spectrum consisted of aliphatic singlets at 6 3.84(4H) for the benzylic protons and 6 5.52(2H) for the bridgehead protons. The protons of anthracene moiety were apparent as two two-proton singlets at 6 8.22 and 7.87, and two two-proton doublets of doublets at 6 7.93 and 7.38. The remaining aryl protons appeared as follows : 6 7.03(dd,2H), 7.11(dd,2H), 7.21(dd,2H), 7.36- 7.43 (m,4H) . Compound 137 was quantitatively dehydrogenated, by refluxing with Pd/C in mesitylene for 60 h, to give 109. 70 The structure of 109 was obvious from its spectra, which were consistent with the C2v symmetry. The 1H NMR spectrum contained a two-proton singlet at 6 5.68 for the bridgehead protons and two two-proton doublets of doublets at 6 7.11 and 7.52 for the benzenoid ring protons. The protons of the anthracene moieties appeared as two four-proton singlets at 6 8.28 and 7.98 and two four-proton doublets of doublets at 6 7.93 and 7.41. The 13C NMR spectrum gave eleven peaks (one aliphatic carbon and ten aromatic carbons) as required by the symmetry. The mass spectrum of 109 showed a strong molecular ion peak at m/g 454. The UV spectrum possessed a set of bands typical of an anthracene, with the longest wavelength absorption at 378 nm. The structure of 109 was further confirmed by its cycloaddition reaction with two equivalents of benzyne to give the known heptiptycene 27 in 50 % yield. The unique arrangement of the two anthracene moieties in triptycene 109 might be useful for synthesizing complex iptycenes, since such molecules can be built up in two direction. Another possible application will be the synthesis of polyiptycenes, which might be potentially useful polymers for heat-resistant materials. For example, a bifuctional dienophile such as 40, in a Diels-Alder 71 cycloaddition with 109, should give epoxypolyiptycene 138.41 A photopolymer from 109 might also be envisioned, via the face-to-face dimerization of its anthracene units. For example, as a model, [3(b,b)b.l.1]triptycene 20 was 43,44 photodimerized to give 139 in 62 % yield. The product is believed to be the head-to-tail isomer. The characteristic feature of the l H NMR spectrum of 139 was the disappearance of the anthracene moiety and the additional formation of the bridgehead protons. The spectrum showed two four-proton singlets at 5 4.27 and 5.12 for the bridgehead protons, and a four-proton singlet at 6 6.84 for the uncoupled benzenoid ring protons. The remaining aryl protons appeared as six sets of four-proton doublets of doublets at 6 6.17, 6.60, 6.85, 6.95, 6.98 and 7.21. The dimer 139, unlike 20, was sparingly soluble in ordinary organic solvents. Upon heating to its melting 72 point, it dissociated to give 20.44 Similarly, photopolymerization of 109 might afford a useful rigid ladder polymer (The photopolymerization of a similar type of compound, 7,16-bis(1-octynyl-7,16-dihydro- heptacene-7,16-diol has been reported).41 E. Synthesis of 6,15[l',2']-Benzeno-2,3,-dibromo-6,15- dihydrohexacene (143). The successful synthesis of 109 via 5,14-dihydro- pentacene synthon 128 led us to explore its analogue 143. Refluxing equivalent amounts of 38 and 128 in xylene for 5 days afforded two regioisomers 140 and 141 (ratio 8:1) in 47 @9000 ‘ Z xylene 7m) The 1H NMR spectra of 140 and 141 were similar to those of 135 and 136. The benzylic protons of 140 appeared as a singlet at 6 3.85 whereas in 141 these protons appeared as an AB quartet at 6 3.91. The major adduct 140 was then dehydrogenated to give 142 in 93 % yield. The structure of 13 142 was supported by its 1H and C NMR and mass spectra. 73 Dehydration of 142 using sulfuric acid in acetic acid gave the desired 143 in 43 % yield. The structure of 143 was clear from its spectra and was confirmed by formation of benzyne adduct 78. 14o Pd“3 , (93%) ”:50; , HOAC ' (“3%) @' ’D- (61%) 1H NMR spectrum of 143 showed a two-proton singlet The at 6 5.64 for the bridgehead protons. The aromatic region consisted of two two-proton singlets at 6 7.94 and 7.67 for the naphthalene ring protons, and two two-proton doublets of doublets at 6 7.11 and 7.50 for the benzenoid ring protons. In addition, the anthracene moiety appeared as follows : 6 8.27(s,2H), 7.96(s,2H), 7.92(dd,2H) and 7.40(dd,2H). The 13 C NMR spectrum gave fifteen peaks (one peak was missing, possibly overlapped at 5 131.68 due to its double 74 intensity). The mass spectrum showed a strong molecular ion peak at m/g 562. Benzyne addition to the anthracene moiety of 143 gave compound 78 in 61 % yield. Its 1H NMR was identical to that of independently synthesized 78 (vide supra). Compound 143 is also a potential synthon for the synthesis of complex iptycenes or polyiptycenes. The dual character of the molecule, anthracene moiety as diene and dibromonaphthalene moiety as aryne equivalent, is very attractive. For example, one might use the anthracene moiety to build up higher iptycenes first (as with synthon 20), then elaborate the aryne equivalent part to make a more complex iptycene. Another possible application might be to use 143 as a monomer to synthesize a polyiptycene. For instance, generation of aryne from the dibromonaphthalene moiety followed by intermolecular Diels-Alder reaction with the anthracene moiety could give polyiptycene 145. [M] Li or Mg 75 In addition, one might also trap intermediate 144 with furan to make the potential monomer epoxytriptycene 146. Heating 146 should then give epoxypolyiptycene 147. 144 F. Conclusions. In this part we have demonstrated the successful synthesis of linear acenes by fusion of o-xylylene to the epoxides 7, 38, 40 and 50, followed by dehydration and dehydrogenation. The 5,14-dihydropentacene 128 thus obtained was applied to the synthesis of potential synthons 109 and '143. The dual fuctionalities in these molecules suggests their use as precursors of complex iptycenes or as monomers to synthesize polyiptycenes. 76 Part III. Synthesis and Reagtigns g: a Eggano[3,4-g]benzo- c fur E ‘val t. Isobenzofuran or benzo[c]furan 129, a reactive 57 The species, has been studied extensively in recent years. application of this compound and its analogues in the Diels- Alder synthesis of polycyclic systems, including natural products, has become recognized. / o 129 133 149 Furano[3,4-f]benzo[c]furan (another name is benzo- [1,2-c:4,5-c']difuran) 133 (trial structure), a l4r-electron heterocycle or a biradical species 149, containing in a sense two units of isobenzofuran is virtually unknown in the literature. The hexaphenyl sulfur analog of 133, that is thieno[3,4-f]benzo[c]thiophene 150, was reported to be a 8 The related bicyclic system 9 stable crystalline compound.5 151 has also been synthesized.5 Ph _Ph ph Ph Ph Ph ph Ph Ph Ph 160 151 Isobenzofuran 129 was first demonstrated to exist as a 60 They transient intermediate by Fieser and Haddadin. reacted 7 with a-pyrone 152 or with tetraphenylcyclopenta- dienone (tetracyclone) 153 to form Diels-Alder adduct 154 or 155, respectively (Fig. 11). Upon heating, the adducts 77 Ph Ph * o 7 Ph Ph 153 O 152 v Ph °“ amnr' Ph W V Ph HH 16" Ph [O6OJ3fl*[0@]‘ I“ 129 7 o o 9 .:.Q . 158(e_x_g,gg_q ) 169(exmendo) Figure 11. Generation and trapping of isobenzofuran intermediate 129. 78 spontaneously lost carbon dioxide or carbon monoxide to produce 156 or 157, which underwent a retro Diels-Alder reaction to give the reactive isobenzofuran intermediate. The isobenzofuran species thus generated was trapped in situ by epoxide 7 to give two adducts, 158 (g;g,gxg) and 159 (ng,gnQQ). The precursors 154 and 155 thus acted as isobenzofuran equivalents. In this part of the thesis, we shall describe the use of furano[3,4-f]benzo[c]furan equivalent 160 to synthesize some novel linearly fused polycyclic compounds. The idea of extending isobenzofurans to the furano-_ [3,4-f]benzo[c]furan 133 came from our needs and observations during this study. First, the failure of being able to use heptacene equivalents 112 and 121 to synthesize the important building blocks 109 and 110 (see discussion in part II) suggested that a third candidate, 5,18:9,14- heptacenediquinone 161, might be necessary. This would eliminate the possible phenomenon of hydrogen walks or rearrangements. Second, the mass spectra of epoxyarenes 116 and 120 (Table 3) showed a base peak at m/g 158, possibly due to a transient intermediate that could be formed by a 79 [oomaflao‘ ——>o[ was] » [ T Iii/0:158 [a «mom ]’——» [woes —» [cor] Wez158 retro Dials-Alder reaction. The unusually strong base peak of m/g 158 suggested that species 133 might be aromatic (14 w electrons). Third, using a synthetic equivalent of 133 (i.e. 160) we might be able to synthesize 161 via a short route. Finally, the structure and properties of species 133 would be worthwhile to investigate, especially to determine whether or not it could be isolated. A. Synthesis of Furano[3,4-f]benzo[c]furan Equivalent (160). Bis-epoxide 40 and tetracyclone 153 are both readily available materials. Thus, cycloaddition of 40 with two equivalents of 153 in refluxing benzene gave bis-adducts 1603 or 160a in high yields. Only one isomer was formed in each case, depending on the stereochemistry of the 80 Ph Ph Ph Ph Ph Ph 666 +2 and —-»M 66666 P" Ph Ph Ph Ph ph 153 403 90% 1608 40a 92% 1‘93 bis-epoxide precursor. The 13 NMR spectrum of the syn adduct 1608 showed two four-proton singlets at 6 3.16 and 5.81 for the bridgehead protons, and two sets of multiplets at 6 6.87-6.99 and 7.26-7.47 for the aryl protons. The anti adduct 160a had a similar spectrum, with the bridgehead protons at 6 3.06 and 5.84 , and the central aromatic protons at 6 7.58 as well as remaining aryl protons at 6 6.87-7.04 and 7.27-7.52. The lack of coupling between the two sets of bridge- head protons indicated that the stereochemistry of both adducts was exo. However, the stereochemistry of the carbonyl groups was not determined. B. Trapping various Dienophiles With Furano[3,4-f]benzo- [c]furan Equivalent. The easy synthesis of 160a makes it a very useful intermediate for the preparation of some linearly fused polycyclic systems. For example, thermal decomposition of 160a followed by trapping of the isobenzofuran moiety with a dienophile in situ would afford compounds with bis-fusion on the furano-[3,4-f]benzo[c]furan 133 backbone (Fig. 12). 81 CH co.c.=cco.cn HJC02C~cozcrg (775) “£05 COZCH3 1603 164 (252-919) o'i»ooooouooo 165(e_1d_ooendo) @$;,» 6666666 163(92'2ndsiafld/vago) Figure 12. Trapping various dienophiles with furano- [3,4-f]benzo[c]furan equivalent 160a. Thus, heating 160a with two equivalents of a dienophile in a sealed tube (xylene as solvent) at l70°for 13 h gave bis- adducts in good yield. The structure of each individual adduct was assigned by its spectra. However, the stereochemistry of the oxygen bridge (syn or anti) was not determined. 82 In the case of adduct 162, both syn and anti isomers were found. The 1H NMR spectrum of anti isomer showed a four-proton singlet at 6 5.91 for the bridgehead protons, a twelve-proton singlet at 6 3.81 for the methyl protons, and a two-proton singlet for the aromatic protons at 6 7.53. The syn adduct had a similar spectrum, whose aromatic protons appeared at 6 7.49. The 13C NMR spectrum of each adduct gave six peaks as required by the symmetry. The mass spectrum of 162 showed a correct molecular ion peak at m/g 442. 66 The simple spectra of TCNE adduct 163 indicated that 1 only one isomer was found. The H NMR spectrum appeared as two singlets at 6 6.93 and 7.98, area ratio 4:2. The 13C NMR gave only six peaks as required by the C symmetry. 2V The naphthaquinone adduct 164 was isolated in 75 % yield. The 1 H NMR spectrum showed two four-proton singlets at 6 3.05 and 5.84 for the bridgehead protons, a two-proton singlet at 6 7.55 for the central aromatic protons, and two sets of four-proton doublets of doublets at 6 7.81 and 8.17 for the "outer" benzenoid ring protons. The stereochemistry of 164 was assigned as exo/exo, the likely thermodynamic product, because the bridgehead protons showed virtually no coupling to each other. The anthraquinone adduct 165, on the other hand, was found to be the endo/endo isomer, a kinetically-controlled 1H NMR spectrum showed obvious coupling product, since the between the bridgehead protons. Its spectrum appeared as two four-proton quartets at 6 3.95 and 5.92 for the 83 bridgehead protons, and a two-proton singlet at 6 7.07 for the central aromatic protons. In addition, the naphthalene moiety appeared as follows : 6 8.55(s,4H), 8.07(dd,4H), and 7.71(dd,4H). The reason for the formation of the kinetic product was probably due to the insolubility of the product (precipitation from the reaction mixture at 170°), which prevented its further conversion to the more stable exo/exo adduct. Trapping of 160a in presence of epoxide 7 gave adduct 166 in 73 % yield. The 1 H NMR spectrum contained two sets of bridgehead protons. One set appeared at J 2.77(q,4H), 4.68(s,4H) and 5.32(q,4H). The corresponding peaks of the other set appeared at 6 2.90(q,4H), 4.78(s,4H) and 5.44(q,4H). The remaining aryl protons gave a multiplet at 6 7.02-7.26. The complicated spectrum of 166 indicated that it was possibly a mixture of the exo/endo isomer 169 and the 61 endo/egg isomer 170. The mass spectrum showed a correct molecular ion peak at m/g 446. Fig. 12 summarizes the successful examples of the trapping of furano[3,4-f]benzo[c]furan equivalent 160 with various dienophiles to construct novel linearly fused polycyclic compounds. Among them, adducts 164 and 165 were 84 dehydrated using sulfuric acid and acetic acid to give the corresponding anthracenes 161 and 171 in high yields. 164 '*. h- (90%) f C) 166 (9:4) ' @@.@@@.@@ 0 111 ’ The insolubility of these compounds in ordinary organic solvents prevented the measurement of their NMR spectra but their structures were supported by IR and mass spectral data as well as by their mode of formation. The mass spectrum of 161 showed a molecular ion peak at m/g 438. The IR spectrum possessed a typical quinone peak at 1680 cm-1. It gave a brownish-orange vat dye with alkaline sodium dithionite, similar to the result reported by Marschalk.64 In concentrated sulfuric acid it gave a dark green solution. Although compound 161 can be synthesized readily, the insoluble property of this compound limited its use as a heptacene equivalent. The structure of 171 was assigned similarly to that of 161. The mass spectrum showed a molecular ion peak at m/g 538. An IR peak of the quinone moiety appeared at 1670 cm-1. The compound gave a dark green solution in concentrated sulfuric acid. 85 C. Mechanism for the Generation of Isobenzofuran or Furano- [3,4-f]benzo[c]furan from 160a. The trapping reactions of 160a with various dienophiles described above possibly proceeded via a step- wise mechanism (via two isobenzofuran moieties) or possibly through the furano[3,4-f]benzo[c]furan 133. For example, possible mechanisms for the formation of the DMAD bis-adduct 162 are illustrated in Fig. 13. Upon heating, compound 160a can lose carbon monoxide to produce 173, which can undergo a retro Diels-Alder reaction to give the isobenzofuran intermediate 174. Species 174 can either be trapped with one equivalent of DMAD to afford monoadduct 175, or undergo further eliminations to generate the furano[3,4-f]benzo[c]furan intermediate 133. In the former case, loss of carbon monoxide and tetraphenylbenzene 177 will produce another isobenzofuran intermediate 176, which can then be trapped with DMAD to give the observed bis-adduct 162. In the latter case, no monoadduct would be involved. Although it seems that a stepwise pathway has more precedent, the intermediate 133 cannot be ruled out. More evidence supporting the existence of species 133 came from the mass spectra of adducts 162-165, all of which showed a base or strong peak at m/g 158. 86 1 mos- 354m] - CH,co,cecco,c H, 12 6" 67 P" H. c0204. 6606 2:2“, 223:2”..6 h 176 l-CO 67 I - "" > [“223] 178 Figure 13. Possible mechanisms for the generation of isobenzofuran or furano[3,4-f]benzo[c]furan 133 from 160a. 87 D. Suggestions for Further Studies. As discussed above, the utility of compound 160a as a synthetic equivalent of furano[3,4-f]benzo[c]furan 133 for the synthesis of linearly fused polycyclic systems was demonstrated. This methodology can be applied to construct novel polycyclic compounds if a suitable dienophile is chosen. To extend the sucessful examples of adducts 164- 166, one can imagine that a Diels-Alder type of polymer might be synthesized choosing benzoquinone or bisepoxide 40 as the dienophiles. For example, 0 1603' * 0 1°“ * $6“ -‘-‘—> ( G¢¢O¢¢ 1. Another feature worthwhile to explore is the isolation of species 133. Isobenzofuran 129 has been isolated via retro Diels-Alder reaction with derivatives of 7. Warrener62 applied 3,6-di(2'-pyridyl)-s-tetrazine 180 as the diene component with 7 to prepare adduct 181, which spontaneously lost nitrogen to form 182. By controlled pyrolysis of 182 at 120°under reduced pressure (0.1 mm), 129 was trapped on a cold finger. Py Py H + N6 016 -—-I——» i Py P’ 7 1 l - 1 ———>"2 0%): —’—"—-> 33- (0.1nun) 182 129 Wiersum63 used l,4-epoxy-1,2,3,4-tetrahydronaphthalene 183 as a starting material. Flash-vaccum pyrolysis (FVP) of 183 at 650°and 0.1 torr in an unpacked quartz tube resulted in the quantitative formation of 129. (3:111: ) ’ 09' 183 m The successful isolation of isobenzofuran by FVP suggests that furano[3,4-f]benzo[c]furan 133 might be isolated through similar experiments. For example, compounds 184 or 185 could be used as its precursors. 185 89 This preliminary study of compound 160 in the synthesis of some linear polycyclic systems opens up a new field to explore. First, by choosing a proper dienophile one can design novel polycyclic compounds. Second, the heterocyclic species related to 133, or its analogs, is a theoretically interesting subject. We expect to see some achievements in this field in the near future. 90 Experimental 1. General Procedure. NMR spectra (1H and 13C) were recorded on a Bruker WM 250 MHz spectrometer using CDCl3 as solvent and (CH Si as the internal reference. UV spectra 3)4 were obtained on a Perkin-Elmer 200 spectrometer. Mass spectra were measured at 70 eV using a Finnigan 4000 spectrometer with the INCOS data system, operated by Mr. Ernest Oliver or Mr. Richard Olson. Some very high melting materials were measured either on a Hitachi M-80A spectrometer with a direct inlet temperature of 300-400 at Ube Industries, Japan, or JEOL HX110 HF spectrometer using field desorption (FD) technique at Michigan State University Mass Spectrometry Facility. Melting points were determined with an electro-thermal melting point apparatus (Fisher Scientific) and are uncorrected.. Anhydrous MgSO4 was the drying agent throughout, silica gel for chromatography was either 70-200 or 230-400 mesh. Microanalysis were performed by Spang Microanalytical Laboratory, Eagle Harbor, Michigan. 2. 1,2,4,5-Tetrabromobenzene (31). To a solution of 1,4-dibromobenzene (236 g, 1 mole) in 1200 mL CCl4 containing iron filings (4.8 g) was added bromine (206 mL, 4 mole) and the mixture was heated at reflux for 20 h. The cooled mixture was slowly added to a stirred, cold saturated Na 80 soln (2 L) until the bromine 2 3 91 color disappeared. The resulting ppt was filtered, washed with water, then methanol and saved. The organic layer of the combined filtrates was separated, dried, and evaporated, The residue was combined with the above ppt and recrystallized from benzene to give 275.8 g (70 %) of 31, 24 181 ); 1H-NMR : 6 7.87 (s). m.p. 180-182 (lit. 3. 6,7-Dibrono-1,4-dihydronaphthalene-1,4-epoxide (38). To a stirred soln of 1,2,4,5-tetrabromobenzene (90 g, 228 mmole) and furan (115 mL) in dry toluene (2 10 at -23°C under argon was added n-butyllithium (250 mmole in 150 mL hexane) dropwise over 4 h. After the mixture slowly came to room temperature, water (50 mL) was added, and the mixture was washed with water, dried, and the solvent removed (rotavap). The resulting yellowish oily solid was recrystallized from methanol to give 48.20 g (70 %) of 38, m.p. 115-117°; ln-NMR : 6 5.64(s,2H), 6.98(s,2H), 7.45(s,2H) 3 13C-NMR : 6 81476, 120.61, 125.43, 142.68, 150.19 7 mass spectrum, m/g (relative intensity) 302 (M+,9), 276(19), 193(100), 113(46), 87(21), 63(25). 8881- Calcd. for C10H6Br20 : C, 39.78 3 H, 2.00. Found : C, 39.86 3 H, 2.07. 4. 2,3-Dibrononaphthalene (49). To ice-cold dry THF (500 mL) was added carefully 18 mL of TiCl followed by 20 g of Zn powder, and the gray mixture 4! was heated at reflux for 30 minutes. Then a soln of 38 (35 g, 116 mmole) in 225 mL of THF .was added dropwise. The mixture was refluxed overnight, cooled and poured into 1 L 92 of cold 10 % HCl. The resulting ppt was filtered, washed with water and air-dried. Recrystallization of the crude product from heptane gave 28.20 g (85 %) of 49, m.p. 138-140° 25d 1 (1it. 139-140° ); H-NMR: 5 7.48(dd,2H), 7.68(dd,2H), 8.15(s,2H). 5. 1,3-Dibrononaphthalene (55). One hundred and ten grams of 5425d was introduced into 100 mL flask and heated. When all the materials was molten, the flask was mounted with a Claisen head, a condenser and a receiver and the distillation system was evaculated to an absolute pressure of 70-200 mm. The flask contents were heated at a pot temperature of 220°; hexachlorocyclopenta- diene distilled over. Distillation was continued until the production of hexachlorocyclopentadiene became very slow and small amounts of solid appeared in the condenser. The dark. residue left in the flask was column chromatographed over silica gel using hexane as the eluent to give 55 ( 9.12 g, 24 %), m.p. 64-66‘(Lit.67 64‘); 1H-NMR : 6 7.50(dd,2H), 7.73(dd,2H), 7.94(s,1H), 8.13(s,1H) ; mass spectrum, m/g (rel. intensity) 288(M+4,27), 286(M+2,48), 284(M+,23), 276(19), 242(100), 205(8), 196(39), 161(46), 126(91). 6. 1,4-Dihydroanthracene—1,4-epoxide (50). To a stirred soln of 2,3-dibromonaphthalene (18.2 g, 63.6 mmole) and furan (120 mL) in dry toluene (450 mL) at room temperature under argon was added n-butyllithium (70 mmole in 70 mL hexane) dropwise over 3 h. The mixture was stirred 93 at room temperature for another 16 h. Methanol (2 mL) was added, and the mixture was washed with water, dried and the solvent removed (rotavap). The resulting ppt was recrystallized from petroleum ether (b.p. 60-90”) to give 259 164-165'): 1H-NMR 10.0 g (81 %) of 50, m.p. 163-165°(1it. : 6 5.80(s,2H), 6.97(s,2H), 7.43(dd,2H), 7.59(s,2H), 7.72(dd,2H). 7. 11,12-Dilethylene-9,10-dihydro-9,10-ethanoanthracene (52) A mixture of anthracene (10.68 g, 60 mmole) and 1,4- 28 (50 mL, cis/trans mixture) was heated in dichloro-z-butene a sealed tube at 190-195° for 48 h. Solvent removal (distillation) gave a black product which was preabsorbed onto alumina. Column chromatography over silica gel and alumina (1:1, alumina on top) using CHZCl -hexane (1:2) as 2 eluent gave 16.8 g (96 %) of a cis/trans mixture of 11,12- bis-chloromethyl-9,10-dihydro-9,10-ethanoanthracene 57, m.p. 144-146°(hexane) ; 1H-NMR : (cis) 6 1.74(m,2H), 2.96(m,2H), 3.30(m,2H), 4.43(s,2H), 7.15(dd,4H), 7.32(dd,4H) ; (trans) 2.46(m,2H), 2.85(m,2H), 3.44(m,2H), 4.55(s,2H), 7.14(dd,4H), 7.32(dd,4H) ; mass spectrum, m/g (relative intensity) 302(M+,l3), 229(3), 215(14), 202(19), 189(7), 178(100), 165(5). To a soln of 57 (15.15 g, 50 mmole) in DMSO (160 mL) and THF (40 mL) was added t-BuOK (16.5 g, 150 mmole) and the brown soln was stirred at room temperature overnight, then poured into- ice-water, and extracted with ether. The organic layer was washed with brine, dried and the solvents 94 removed (rotavap). The resulting ppt was recrystallized from hexane to give 10.24 g (89 %) of diene 52, m.p. 156-157‘ 26 1 (lit. 157-157.5°) ; H-NMR : 6 4.87(s,2H), 5.06(s,2H), 5.16(s,2H), 7.12(dd,4H), 7.31(dd,4H). 8. 1,4:5,8-Diepoxy-1,4,5,8-tetrahydroanthracene (40). To a stirred soln of 1,2,4,5-tetrabromobenzene 31 (39.4 g, 0.1 mole) and furan (freshly distilled, 120 mL) in dry toluene (1400 mL) at -23’C under argon was slowly added n- BuLi (0.22 mole in 150 mL hexane) for 4 h. After addition the mixture was slowly allowed to warm to room temperature and stirred overnight. Water '(50 mL) was added and the mixture was stirred for a few minutes. The organic layer was washed with water and dried. Solvent removal (rotavap) gave a gummy yellow solid which partially dissolved on addition of methanol (120 mL). The off-white crystals which remained (7.03 g) were recrystallized from acetone to give small white plates of anti isomer 40a. The methanol soln was evaporated to dryness. The residue was either recrystallized from methanol two to three times or column chromatographed over silica gel using EtOAc as the eluent to give the pure syn isomer 405 (6.62 g). The total yield of both isomers was 65 %. Their 1H NMR spectrum were identical to those of the literature14b. 9. 5,14[1',2']Benzeno-5,14-dihydropentacene (20). Method .A : A soln of 38 (18.12 g, 60 mmole) and anthracene (10.68 g, 60 mmole) in xylene (700 mL) was heated 95 at reflux for 4 days. The solvent was removed (rotavap) and the residue was recrystallized from THF-MeOH to give 43 (27.65 g, 96 %) as fine off-white crystals, m.p. 264-266‘: 1H-NMR : 6 2.24(s,2H), 4.4l(s,2H), 4.89(s,2H), 7.03(dd,2H), 7.16(dd,2H), 7.24(m,4H), 7.40(s,2H) ; 13c-NMR.: 6 47.21, 48.25, 80.82, 123.61, 123.81, 124.17, 125.31, 125.90, 126.17, 128.17, 140.10, 143.84 : mass spectrum, m/g (rel. intensity) 480(M+,4), 462(1), 302(2), 289(7), 276(9), 203(26), 191(100), 178(53). To a suspension of 43 (19.2 g, 40 mmole) in EtOH (1400 mL) was added dropwise 45 mL of 72 % perchloric acid and the soln was heated at reflux overnight. The cooled soln was poured into ice-water (1.5 L). The resulting solid was filtered, washed with water, methanol and dried. Recrystallization from THF-MeOH gave a tan solid, which was further recrystallized from toluene to give 44 (12.01 g, 65%) as colorless flakes, m.p. 386-388°(dec.) ; 1H-NMR : 6 5.51(s,2H), 7.04(dd,4H), 7.43(dd,4H), 7.60(s,2H), 7.94(s,2H) ; 13c-NMR : 6 53.62,, 120.68, 123.84, 125.78, 131.64, '144.02, 155.16 (two peaks were missing due to quarternary carbons) ; mass spectrum65, m/g (rel. intensity) 464(35), 462(100), 460 (85). To a stirred soln of 44 (6.93 g, 15 mmole) and furan (60 mL)in dry THF (1200 mL) at -78°under argon was added n-BuLi (17.25 mmole in 150 mL hexane) dropwise over 5 h. The mixture was allowed to come slowly to room temp and stirred overnight. MeOH (2 mL) was added, and the mixture was washed with water, dried and concentrated. The residue was 96 chromatographed using CHzclz-hexane (1:2) as eluent to give 45 (3.89 g, 70 %) as light yellow crystals, m.p. 188-190o (MeOH) ; lH-NMR : 6 5.48(s,2H), 5.72(s,2H), 6.88(s,2H), 6.99(m,4H), 7.39(m,4H), 7.44(s,2H), 7.65(s,2H) ; lac-NMR : 6 53.92, 81.88, 118.37, 121.64, 122.17, 123.70, 125.52, 125.61, 127.43, 141.75, 145.82 ; mass spectrum, m/g (rel. intensity) 370(M+,1), 341(1), 303(1), 170(2), 149(4), 84(5), 40(100). To a suspension of TiCl4 (6.38 mL) in dry THF (500 mL) under argon at 0°was added 8.9 g of Zn powder. The gray suspension was heated at reflux for 30 minutes and a soln of 45 (4.44 g, 12 mmole) in 100 mL THF was added dropwise. After 8 h at reflux, the cooled mixture was poured into dil. HCl (1 L). The purple mixture was extracted with CH2C12 and the organic layer was washed with water and dried. Solvent removal gave a solid which was recrystallized from cyclohexane to give 20 (3.44 g, 81 %), m.p. 221-222'32 3 1H- NMR : 6 5.54(s,2H), 7.05(dd,4H), 7.38(dd,2H), 7.46(dd,4H), 7.88(s,2H), 7.91(dd,2H), 8.23(s,2H) ; 13c-NMR : 6 53.65, 121.31, 123.81, 124.96, 125.61, 125.75, 127.99, 130.52, 131.69, 141.10, 144.19 ; mass spectrum, m/g (rel. intensity) 354(M+,100), 353(66), 278(3), 176(69) ; Anal : Calcd. for C28H18 : C, 94.88; H, 5.12. Found : C, 94.81; H, 5.15. Mathod B : To a soln of diene 52 (11.50 g, 50 mmole) and 49 (14.30 g, 50 mmole) in dry toluene (l L) under argon was added n-BuLi (55 mmole in 150 mL hexane) dropwise over 3 h. The mixture was stirred at room temperature overnight, then quenched with methanol (3 mL). The resulting ppt was 97 filtered and saved. The filtrate was washed with water, dried and concentrated. The resulting solid was combined with the above ppt and recrystallized from CHZClz-hexane to lH-NMR : 6 3.82 give 62 (14.24 g, 80 %), m.p. 298—300': (s,4H), 4.92(s,2H), 6.96(dd,4H), 7.34(m,6H), 7.58(s,2H), 7.70(dd,2H) ; mass spectrum, m/g (rel. intensity) 356(M+,4), 290(6), 215(3), 202(3), 191(5), 180(5), 179(100), 178(32). A soln of 62 (14.60 g, 41 mmole) in xylene (400 mL) containing 1 g of 10 % Pd/C under argon was heated at reflux for 48 h. The hot soln was filtered, and the catalyst was washed with methylene chloride (100 mL). The combined filtrate was concentrated (rotavap) to give colorless crystals of 20 (14.22 g, 98 %), m.p. 220-222“. Method C : A soln of 50 (786 mg, 4.05 mmole) and anthracene (712 mg, 4.0 mmole) in xylene (20 mL) was heated at reflux for 72 h. The solvent was removed (rotavap) and the residue was recrystallized from CHC13-hexane to give 63 (1.38 g, 93 %) as tan crystals, m.p. > 310°(dec.) : 1H-NMR : 6 2.36(s,2H), 4.49(s,2H), 5.08(s,2H), 7.02(dd,2H), 7.17(dd,2H), 7.24(dd,2H), 7.33(dd,2H), 7.40(dd,2H), 7.52(s,2H), 7.72(dd,2H) ; 13c-NMR : 6 47.52, 49.21, 81.23, 116.84, 123.53, 123.79, 125.64, 125.76, 126.08, 128.08, 132.61, 141.41, 144.01, 144.57 3 mass spectrum, m/g (rel. intensity) 372(M+,1), 354(2), 353(3), 203(10), 191(28), 181(100), 178(39), 168(57), 139(10), 106(9), 91(18). A soln of 63 (744 mg, 2 mmole) and conc. HCl (5 mL) in acetic anhydride (20 mL) was heated at reflux for 5 h. The cooled mixture was poured into 100 mL ice-water, and the 98 resulting solid was filtered, washed with water and dried. The solid was column chromatographed over silica gel, first elueting with hexane, then with CHZClz-hexane (1:4) to give 20 (474 mg, 67 %), m.p. 221-222'. Method D : A soln of 1,4-dihydronaphtha1ene-l,4-epoxide33 (1.44 g, 10 mmole) and 52 (2.30 g, 10 mmole) in toluene (40 mL) was heated at reflux for 72 h. The solvent was removed (rotavap) and the soln was triturated with hexane to give 64 (3.33 g, 89 %), m.p. 209-2113 (toluene) : 1H-NMR : 6 l.87(dd,2H), 2.20( dd,2H), 2.82(dd,2H), 4.78(s,2H), 4.92(s,2H), 6.85-6.91(m,4H), 7.05-7.23(m,8H) : 13c-NMR : 6 30.47, 42.01, 55.77, 84.98, 118.66, 122.39, 122.50, 124.09, 124.22, 126.40, 143.06, 145.46, 146.39 ; mass spectrum, m/g (rel. intensity) 374(M+,11), 356(6), 256(68), 215(26), 202(23), 178(92), 90(20). A soln of 64 (2.99 g, 8 mmole) and conc. HCl (15 mL) in acetic anhydride (60 mL) was heated at reflux for 12 h. The cooled mixture was poured into 300 mL ice-water, and the resulting ppt was filtered, washed with water and dried. Column chromatography using CHZClz-hexane (1:4) as the eluent gave 65 (1.59 g, 56 %) as colorless crystals, m.p. 217-219'; lH-NMR : 6 2.32(m,1H), 2.72(m,lH), 2.96(m,1H), 4.32(s,lH), 4.87(s,lH), 6.55(s,1H), 7.11(m,4H), 7.31(m,6H), 7.32(s,1H), 7.38(s,1H), 7.64(m,2H) ; mass spectrum, m/g (rel. intensity) 356(M+,29), 354(7), 353(5), 352(4), 278(2), 176(13). A soln of 65 (1.07 g, 3 mmole) in mesitylene (50 mL) containing 150 mg of 10 % Pd/C was heated under argon at reflux for 72 h. The hot soln was filtered and the catalyst 99 . was washed with methylene chloride (20 mL). The combined filtrate was concentrated under reduced pressure to give 20 (1.01 g, 95 %), m.p. 220-222‘. 10. Dials-Alder adduct of 20 with tetracyanoethylene (69). A soln of 20 (354 mg, 1 mmole) and TCNE (128 mg, 1 mmole) in benzene (50 mL) was heated at reflux for 3 h. The green soln (charge transfer complex) gradually faded and a white ppt formed. The cooled soln was filtered, and washed. with benzene to give 69 (472 mg, 98 %) as a colorless powder, m.p. ca 288'(dec.) (acetone-hexane) : 1H-NMR : 6 5.69(s,2H), 5.75(s,2H), 6.90(dd,2H), 7.00(dd,2H), 7.37(dd,2H), 7.39 (dd,2H), 7.48(dd,2H), 7.64(dd,2H), 7.82(s,2H) ; mass spectrum (retro Diels-Alder reaction), m/g (rel. intensity» 354(98), 353(67), 352(57), 128(53), 76(52), 58(28), 43(100) 53g; : Calcd. for C H N : C, 84.63 : H, 3.76. Found : 34 18 4 C, 84.41 : H,3.90. 11. Dials-Alder adduct of 20 with dimethyl acetylene- dicarboxylate (70). A soln of 20 (531 mg, 1.5 mmole) and DMAD (147 mg, 1.5 mmole) in benzene (20 mL) was heated at reflux for 5 h. The resulting ppt was filtered, washed with hexane to give 70 (707 mg, 95 2), m.p. 304-306“; lH-NMR : 6 3.73(s,6H), 5.31(s,2H), 5.35(s,2H), 6.89-6.98(m,6H), 7.27-7.35(m,6H), 7.42(s,2H) ; mass spectrum, m/g (rel. intensity) 496(M+,11), 481(5), 437(13), 398(17), 370(21), 354(94), 341(22), 243(32), 213(39), 178(51), 165(43), 149(67), 121(59), 100 105(94), 91(87), 85(82), 44(100) ; Anal : Calcd. for C34H24O4 : C, 82.24; H, 4.87. Found : C, 82.07; H, 4.95. 12. Diels-Alder adduct of 20 with.maleic anhydride (71). A soln of 20 (708 mg, 2 mmole) and MA (196 mg, 2 mmole) in xylene (20 mL) was heated at reflux for 5 h. The resulting white ppt was filtered, washed with hexane to give 71 (868 mg, 96 %) as colorless crystals, m.p. 320-322.; 1H- NMR : 6 3.38(s,2H), 4.71(s,2H), 5.40(s,2H), 6.92(dd,2H), 7.02(dd,2H), 7.13(dd,2H), 7.25(dd,2H), 7.32(dd,2H), 7.39 (s,2H), 7.41(dd,2H) ; mass spectrum (EI), m/g (rel. intensity) 453(M+1,2), 384(2), 355(7), 251(4), 99(100), 85(65) ; Anal : Calcd. for C H O : C, 84.94; H, 4.45. 32 20 3 Found : C, 84.70; H, 4.59. 13. Improved synthesis of 5,14[1',2']:7,12[1',2']dibenzeno- 5,7,12,14-tetrahydropentacene (24). A mixture of 20 (354 mg, 1 mmole), benzenediazonium-z- carboxylate hydrochloride (185 mg, 1 mmole) and propylene oxide (2 mL) in 10 mL of 1,2-dichloroethane was heated at reflux for 3 h. Diethyl carbitol (5 mL) was added and the solvents distilled until the head temperature reached 150° . Maleic anhydride (110 mg) was added and the mixture refluxed for 15 minutes. To the cooled mixture was added a soln of 0.4 g of KOH in 6 mL of MeOH-HZO (2:1). The mixture was chilled in ice, and the resulting solid was filtered, washed with MeOH-H 0 (4:1) and dried. Recrystallization from CCl4 2 gave 24 (280 mg, 65 %) as colorless needles, m.p. ca 465° 14a 0 (dec.) (lit. 483 1 34 ) ; H-NMR : 6 5.30(s,4H), 6.92(dd,8H), 7.28(dd,8H), 7.43(s,2H). 14. 5,16[1',2']:7,14[1',2']Dibenzeno-5,7,14,16-tetrahydro- hexacene (76). A soln of 20 (708 mg, 2 mmole) and 1,4-dihydronaphthalene 1,4-epoxide33 (317 mg, 2.2 mmole) in xylene (60 mL) was heated at reflux for 72 h. The solvent volume was reduced (rotavap) and the soln was triturated with hexane. The resulting ppt was collected to give 72 (906 mg, 91 %) as a tan solid, m.p. ca 367°(dec.) ; 1H-NMR : 6 1.97(s,2H), 4.22(s,2H), 4.80 (s,2H), 5.30(s,2H), . 6.88(dd,2H), 6.92(dd,2H), 6.97(dd,2H), 7.06(dd,4H), 7.18(dd,2H), 7.24(dd,2H), 7.25(s,2H), 7.33 (dd,2H) ; 13C-NMR : 6 47.25, 48.85, 53.97, 81.13, 118.63, 119.62, 123.41, 123.53, 125.01, 125.89, 126.16, 141.17, 141.54, 142.94, 145.29, 145.58, 146.71 (two peaks were missing) ; mass spectrum, m/g (rel. intensity) 498(M+,43), 480(10), 472(42), 457(100), 380(31), 367(76), 354(29), 353(33), 352(29), 265(6), 252(7), 239(9), 178(10), 131(19), 118(13). To a soln of 72 (747 mg, 1.5 mmole) in acetic anhydride (30 mL) was added slowly 4 mL of conc. HCl, and the mixture was heated at reflux for 10 h. The cooled soln was poured into ice-water, and extracted with methylene chloride. The extract was washed with 10 % Na2C03, concentrated. The residue was column chromatographed using water, dried and CHZClz-hexane (1:4) as eluent to give 76 (382 mg, 53 %) as colorless crystals, m.p.>335°(dec.) : 1H-NMR : 6 5.31(s,2H), 102 5.41(S,2H), 6.83-6.95(m,6H), 7.25-7.34(m,8H), 7.48(s,2H), 7.63(dd,2H), 7.68(s,2H) : 13C-NMR : 6 53.59, 53.96, 119.80, 121.44, 123.38, 123.51, .124.06, 125.03, 125.41, 125.55, 125.85, 127.35, 131.66, 141.73, 142.07, 142.89, 144.65, 145.24, 145.33 ; mass spectrum, m/g (rel. intensity) 480 (M+,8), 472(8), 457(16), 396(6), 384(14), 178(100), 144(56), 115(26), 84(27), 43(58) ; UV (cyclohexane) Amax 324 nm (6 30,452), 310(30,408), 289(31,876), 279(32,103), 272 (32,057), 251(33,348), 227(55,284) ; Anal : Calcd. for C38H24 : C, 94.97; H, 5.03. Found : C, 95.13; H, 4.95. 15. 5,16[1',2']:7,14[1',2']Dibenzeno-10,11-dibr0lo- 5,7,14,16-tetrahydrohexacene (78). A soln of 20 (1.062 g, 3 mmole) and 38 (997 mg, 3.3 mmole) in xylene (160 mL) was heated at reflux for 72 h. The soln was cooled, and the resulting ppt collected and saved. The filtrate was concentrated (rotavap), then triturated with acetone (15 mL). The solid was filtered, washed with a small amount of acetone and combined with the above ppt. Recrystallization from xylene gave 77 (1.75 g, 89 %) as a colorless solid, m.p. ca 410°(dec.) ; 1H-NMR : 6 1.57(s,2H), 4.08(s,2H), 4.54(s,2H), 5.36(s,2H), 6.91 (dd,2H), 6.99(dd,2H), 7.05(dd,2H), 7.l4(dd,2H), 7.27(s,2H), 7.28(s,2H),7.30(dd,2H), 7.41(dd,2H) : 13c-NMR : 6 46.80, 48.25, 54.05, 80.47, 119.47, 121.83, 123.43, 123.51, 123.58, 124.16, 125.11, 125.23, 126.01, 140.78, 141.07, 143.16, 145.15, 145.68, 147.69. A mixture of 77 (1.312 g, 2 mmole), acetic acid (300 mL) 103 and conc. H2804 (8 mL) was heated at reflux overnight. The cooled soln was poured into ice-water and extracted with methylene chloride. The extract was washed with 20% Na2C03, water, dried, and concentrated.’ Flash column chromatography using CHZClz-hexane (1:3) as eluent gave 78 (778 mg, 61 %) as a colorless solid, m.p. >4367dec.); 1H-NMR: 6 5.34(s,2H), 5.40(s,2H), 6.86-6.99(m,6H), 7.25-7.35(m,6H), 7.49(s,2H), 7.50(s,2H), 7.88(s,2H) ; 13c-NMR : 6 53.39, 53.90, 119.94, 120.28, 121.30, 121.54, 123.43, 123.65, 125.11, 125.67, 131.37, 131.56, 141.12, 143.13, 143.59, 144208, 145.17 (two peaks were missing) ; mass spectrum,65 m/g (rel. intensity) 640(47), 638(100), 636(35) :UV (cyclohexane) A 337 nm (6 max 20,274), 323 (20,175), 293(21,412), 282(21,371), 273 (21,091), 249(28,068), 228(25,580), 221(25.288) : Anal : Calcd. for C38H22Br2 : C, 71.49; H,3.47. Found : C, 71.32; H, 3.40. 16. 5,18[1',2']:7,16(1-,2-]Dibenzeno-5,7,16,18-tetrahydro- heptacene ( 81) . A soln of 20 (708 mg, 2 mmole) and 50 (407.4 mg, 2.1 mmole) was heated at reflux for 4 days. Evaporation of the solvent (rotavap) gave a tan solid which was recrystallized from cnc13-petroleum ether (30-60°) to yield a mixture of 79 and 80 (997 mg, 91 %) as light yellow crystals, m.p. 304- 306° (dec.) ; 1H-NMR : (major product) 6 2.12(s,2H), 4.28 (s,2H), 4.93(s,2H), 5.31(s,2H), 7.25(s,2H),7.43(s,2H) ; (minor product) 2.29(s,2H), 4.36(s,2H), 4.99(s,2H), 5.35 (s,2H), 7.33(s,2H), 7.45(s,2H). The remaining peaks were too 104 complex to assign to individual isomers. They appeared as follows, with areas assigned for the sum of both products : 6 6.84-6.96(m,8H), 7.08(dd,2H), 7.13(dd,2H), 7.2l(dd,2H), 7.24(dd,2H), 7.30(dd,2H), 7.37(m,8H), 7.69(m,6H). To a suspension of 79 and 80 (548 mg, 1 mmole) in 20 mL ethanol was added 2 mL of 72 % perchloric acid and the mixture was heated at reflux for 5 h. The cooled soln was poured into 100 mL ice-water, extracted with CHZClZ, dried, and concentrated. Column chromatography of the crude product over silica gel using benzene-hexane (1:2) as eluent gave 81 (217 mg, 41 %)as a colorless solid which was recrystallized from 1,2-dichloroethane, m.p. >430°(dec.) 3 1H-NMR : 6 5.33 (s,2H), 5.44(s,2H), 6.86(dd,2H), 6.91(dd,2H), 6.98(dd,2H), 7.27-7.38(m,8H), 7.51(s,2H), 7.80(s,2H), 7.89(dd,2H), 8.18 (s,2H) 3 13C-NMR : 6 53.49, 54.03, 121.08, 122.85, 123.41, 123.48, 125.03, 125.62, 128.99, 129.16, 132.53, 138.67, 140.75, 141.43, 141.89, 145.39, 146.02 : mass spectrum,35 m/g (rel. intensity) 530(Mf,100), 354(12), 353(12), 352(36), 278(8), 62(69), 59(25), 27(76) 3 UV (cyclohexane) Amax 374 nm (e 3590), 355(5310), 337(4770), 320(3125), 295(20,080),286 (21,450), 278(23,520) 3 Anal Calcd. for C42H26 : C, 95.06; H, 4.94. Found : C, 94.77; H,5.22. 17. 7,12[1'.2']Benzeno-15,16-dinethylene-5,14-ethano— 5,7,12,14-tetrahydropentacene (83). A mixture of 20 (7.08 g, 20 mmole) and 1,4-dichloro-2- butene (50 mL, cis/trans mixture) was heated in a sealed tube at 190-195 ' C for 3 days. The solvent was removed by 105 distillation to give a black product which was preabsorbed onto silica gel. Column chromatography using CHZClz-hexane (1:3) as eluent yielded 6.31 g (66 %) cis/trans mixture of 82, m.p. ca 265°(dec.) 3 1H-NMR : (cis) 6 2.32(dd,2H), 2.92 (dd,2H), 3.25(dd,2H), 4.32(s,2H), 5.35(s,2H) 3 (trans) 2.31 (dd,2H), 2.75(dd,2H), 3.36(dd,2H), 4.43(s,2H), 5.36(s,2H). The remaining aromatic peaks were too complex to assign to individual isomers. They appeared as follows :6i6.89(dd), 7.01(dd), 7.06(dd), 7.24(dd), 7.29(dd), 7.36(s), 7.39(dd) 3 mass spectrum, m/g (rel. intensity) 480(5), 478(M+,5), 379(9), 365(5), 354(62), 334(15), 297(9), 178(39), 121(32), 106(100), 105(90). To a soln of 82 (5.74 g, 12 mmole) in DMSO (80 mL) and THF (20 mL) was added t-BuOK (4.03 g, 36 mmole) and the soln was stirred at room temperature overnight. The mixture was poured into ice-water and extracted with ether. The organic layer was washed with brine, dried and the solvent removed (rotavap). Column chromatography using CH ClZ-hexane (1:4) 2 as eluent gave 83 (4.29 g, 88 %) as light yellow crystals, m.p. ca 266°(dec.) 3 1H-NMR : 6 4.75(s,2H), 5.05(s,2H), 5.20(s,2H), 5.34(s,2H), 6.89(dd,2H), 6.96(dd,2H), 7.03 (dd,2H), 7.22(dd,2H), 7.28(dd,2H), 7.32(dd,2H), 7.36(s,2H) ; 13c-NMR : 6 40.83, 54.99, 105.02, 119.30, 123.07, 123.33, 123.44, 125.00, 125.07, 126.18, 138.64, 141.79, 143.54, 143.82, 145.28, 145.33 3 mass spectrum, m/g (rel. intensity) 406(M+,76), 391(9), 354(80), 228(34), 203(26), 195(35), 178(100), 163(17), 151(15), 91(53), 43(39). 106 18. 5,18[1',2']:7,16[1',2']Dibenzeno-11,12-dibromo- 5,7,16,18-tetrahydroheptacene (86). A soln of 83 (1.218 g, 3 mmole) and 38 (0.997 g, 3.3 mmole) in xylene (60 mL) was heated at reflux for 60 h. The cooled soln was concentrated and triturated with hexane. The resulting ppt was filtered and washed with hexane to give 84 (1.72 g, 81%) as a tan solid, m.p. 327-328°(dec.) 3 1H-NMR: 6 l.78(dd,2H), 2.13(dd,2H), 2.72(dd,2H), 4.67(s,2H), 4.83(s,2H), 5.28(s,2H), 6.79(dd,2H), 6.89(dd,2H), 6.96 (dd,2H), 7.10(dd,2H), 7.28(S,2H), 7.34(dd,4H), 7.37(S,2H) 3 mass spectrum, m/g (rel. intensity) 710(M+4,1), 708(M+2,2), 706(M+,l), 432(2), 354(1), 276(1), 252(2), 178(3), 105(4), 91(8), 44(100). To a seln of 84(1.416 g, 2 mole) in ethanol (300 mL) was added slowly 15 mL of 72 % perchloric acid and the mixture was heated at reflux for 16 h. The cooled mixture was poured into ice-water, extracted with methylene chloride and dried. Evaporation of the solvent and column chromatography of the crude product using CH ClZ-hexane (1:3) as eluent 2 gave 85 (787 mg, 57 %), m.p. >360°(dec.) 3 1H-NMR : 6 2.25 (dd,1H), 2.68(dd,1H), 2.87(dd,1H), 4.23(s,1H), 4.77(s,lH), 5.34(s,2H), 6.43(s,lH), 6.92(m,4H), 7.08(dd,2H), 7.l4(s,1H), 7.19(s,lH), 7.25(m,4H), 7.32(dd,2H), 7.35(s,1H),7.36(s,1H), 7.86(s,lH), 7.89(s,1H). A soln of 85 (690 mg, 1 mmole) in mesitylene (20 mL) containing 100 mg of 10 % Pd/C under argon was heated at reflux for 4 days. The hot soln was filtered and the solvent removed under reduced pressure to give 86 (647 mg, 107 94 %), m.p. >415°(dec.) 3 ln-NMR : 6 5.32(s,2H), 5.42(s,2H), 6.85(dd,2H), 6.91(dd,2H), 6.98(dd,2H), 7.25(dd,2H), 7.29 (dd,2H), 7.35(dd,2H), 7.49(s,2H), 7.77(s,2H), 8.06(S,2H), 8.20(s,2H) 3 13c-NMR : 6 53.47, 54.03, 119.92, 120.93, 121.06, 123.43, 123.70, 123.99, 124.77, 125.11, 125.81, 130.86, 132.09, 141.00,. 145.34, 147.50 (five peaks were missing due to its low solubility) 3 mass spectrum,65 n/g (rel. intensity) 690(65), 688(100), 686(40) 3 Ann; : Calcd. for C42H24Br2 : C, 73.273 H, 3.51. Found : C, 73.02, H, 3.69. 19. Dimethyl 5,14[l',2']:7,12[1-,2']dibenzeno—5,7,12,14- tetrahydropentacene-z , 3-dicarboxylate ( 88) . A soln of 83 (812 mg, 2 mmole) and dimethyl acetylene- dicarboxylate (2 mL) in xylene (20 mL) was heated at reflux for 56 h. Solvent removal (rotavap) gave a yellow oil which was column chromatographed using EtOAc-hexane (1:3) as eluent to yield 88 (950 mg,87 %) as colorless crystals, m.p. 1 240-242‘3 H-NMR : 6 3.80(s,6H), 5.29(s,2H), 5.33(s,2H), 6.87-6.92(m,6H), 7.22-7.33(m,6H), 7.40(s,2H), 7.58(s,2H) 3 13C-NMR : 52.38, 53.53, 53.88, 119.93, 123.41, 123.63, 123.71, 125.07, 125.42, 129.04, 141.11, 143.03, 143.99, 145.18, 148.77, 167.86 (three peaks were missing) 3 mass spectrum, m/e (rel. intensity) 546(M+,52), 487(3), 428(13), 427(14), 263(24), 258(28), 252(89), 213(44), 206(24), 178 (31), 59(80), 44(100) 3 Ann; : Calcd. for C38H26°4 : C, 83.503 H, 4.79. Found : C, 83.66: H, 4.58. 108 20. 5,22[1',2']:7,20[1',2']:11,16[1'",2"']Tribenzeno_ 5,7,11,16,20,22-hexahydrononacene (90). A soln of 20 (1.77 g, 5 mmole) and 45 (1.887 g, 5.1 mmole) in xylene (50 mL) was heated at reflux for 5 days. Evaporation of the solvent and recrystallization of the residue from 1,2-dichloroethane-hexane gave adduct 89 (3.19 g, 88 %) as light yellow crystals, m.p. ca 335°(dec.) 3 1H- NMR : 6 l.85(s,2H), 4.06(s,2H), 4.75(s,2H), 5.30(s,2H), 5.47 (s,2H), 6.86-7.07(m,12H), 7.21(s,2H), 7.30(s,2H), 7.32-7.41 (m,8H), 7.67(s,2H). To a suspension of 89 (2.172 g, 3 mmole) in 70 mL EtOH was added dropwise 6 mL of 72 % perchloric acid, and the soln was heated at reflux for 5 h. The cooled mixture was poured into 200 mL ice-water. The resulting solid. was extracted with methylene chloride, dried and evaporated to dryness. The crude product was chromatographed over silica gel with benzene-hexane (1:2) as eluent to give 90 (1.48 g, 70 %) as colorless crystals from toluene, m.p. ca 430°(dec.) '3 1H-NMR : 6 5.31(s,2H), 5.39(s,2H), 5.47(s,2H), 6.83 (dd,2H), 6.90(dd,2H), 6.94(dd,2H), 7.00(m,4H), 7.24(dd,2H), 7.28(dd,2H), 7.33(dd,2H), 7.40(m,4H), 7.47(s,2H), 7.72 (s,2H), 7.78(s,2H), 8.01(s,2H) 3 13c-NMR : 6 53.45, 53.59, 53.95, 119.84, 121.08, 121.25, 123.41, 123.58, 123.75, 125.03, 125.30, 125.64, 128.24, 129.06, 130.39, 140.68, 141.34, 142.96, 144.27, 145.19, 145.34 3 mass spectrum, n/g (rel. intensity) 706(M+,100), 528(17), 462(10), 446(5), 354 '(48), 286(8), 252(10), 178(10) 3 UV (cyclohexane) Amax 371 nm (e 5650), 352(6895), 335(6265), 319(4840), 286(80,000), 109 277(62,600), 266(65,910), 260(63,025), 248(36,975), 238 (35,695) 3 Anal : Calcd. for C56H34 : c, 95.15; H, 4.85. Found : C, 94.813 H, 5.19. 21. Diels-Alder adduct of 90 and DMAD (91). A mixture of 90 (706 mg, 1 mmole) and dimethyl acetylene- dicarboxylate (1 mL) in 1,2-dichloroethane (20 mL) was heated at reflux for 3 days. The cooled soln was concentrated and triturated with hexane. The resulting solid was filtered and recrystallized from CHCl3-hexane to give 91 (704 mg, 83 %) as colorless crystals, m.p. > 360°3 lH-NMR : 6 3.65(s,6H), 5.14(s,2H), 5.18(s,4H), 5.20(s,2H), 6.78(dd,4H), 6.85(dd,4H), 6.91(dd,2H), 7.15-7.26(m,10H), 7.27(s,4H), 7.28(s,2H) 3 13c-NMR : 6 52.20, 52.21, 53.67, 53.81, 53.82, 119.52, 119.66, 123.26, 123.36, 124.91, 141.12, 142.30, 142.70, 142.84, 145.00, 145.11, 145.36, 145.43, 145.54, 147.19, 147.41, 165.88 (nine peaks were 65 showed M+ at n/n 849. missing) 3 the mass spectrum 22. Syn-5,26[1',2']:7,24[1-,2']:11,20[1fl52"q:13,18[1'-,2'-]- tetrabenzeno-5,7,11,13,18,20,24,26-octahydroundecacene (98). A mixture of syn-40 (1.05 g, 5 mmole), 20 (3.54 g, 10 mmole) and xylene (40 mL) in a sealed tube was heated at 180° for 72 h. The ppt that deposited in the cooled soln [was filtered and saved. The filtrate was reduced to half volume (rotavap), and the resulting solid in the cooled soln was filtered and combined with the above ppt to give a mixture 110 of 96 and 97 (NMR ratio 1:1, 3.21 g, 70 %) as a tan solid, m.p. > 400°(dec.) ; 1n-NMR : (97) 6 1.85(s,4H), 4.l9(s,4H), 4.71(s,4H), 5.23(s,4H) 3 (96) 6 l.99(s,4H), 4.23(s,4H), 4.74 (s,4H), 5.28(s,4H); the remaining aryl peaks were too complicated to assign to individual isomers, they appeared as follows : 6 6.76(s), 6.86-6.94(m), 6.95(s), 7.02-7.08(m), 7.16(s), 7.12-7.21(m), 7.23(s), 7.25-7.33(m) 3 mass spectrum35 (retro Diels-Alder reaction), n/e (rel. intensity) 564 (M+-20,4), 538(3), 380(100), 354(64), 210(5). To a suspension of a mixture of 96 and 97 (2.75 g, 3 mmole) in ethanol (250 mL) was added slowly 15 mL of 72 % perchloric acid and the soln was heated at reflux for 8 h. The cooled soln was poured into ice-water and the resulting ppt filtered, washed with water, dried. The crude product was column chromatographed over silica gel using benzene- hexane (1:2) as eluent to give 98 (1.22 g, 46 %) as colorless crystals, m.p. > 450°; 1H-NMR : 6 5.290(s,4H), 5.361(S,4H), 6.802-6.835(dd,4H), 6.878-6.951(m,8H), 7.212- 7.328(m,12H), 7.449(s,4H), 7.688(s,4H), 7.946(s,2H) 3 13c- NMR : 6 53.502, 54.006, 119.840, 121.053, 123.404, 123.554, 125.040, 125.578, 130.371, 140.675, 142.989, 144.430, 145.225, 145.402 (four peaks were missing); mass spectrum,35 n/g (rel. intensity) 883(M+,12), 882(40), 704(2), 446(10), 384(52), 354(100), 268(4), 252(4), 178(2), 57(15) 3 UV (cyclohexane) A 372 nm ( e 6634), 353(8230), 335(8230), max 320(7588), 296(96,811), 280(59,910), 27l(66,075), 264 (112,466), 255(82,616), 249(69,408), 242(65,498) 3 Anal. Calcd. for C7OH42 : C, 95.213 H, 4.79. Found : C, 94.97; H, 111 5.02. 23. Anti-5,26[1',2']:7,24[1',2']:11,20[1”52"U: 13.18[1".2"]tetrabenzeno—5,7,11,13,18,2o,24,26- octahydroundecacene (103). A mixture of anti-40 (1.05 g, 5 mmole), 20 (3.54 g, 10 mmole) and xylene (40 mL) in a sealed tube was heated at 180’ for 72 h. Work up as above gave a mixture of 101 and 102 (NMR ratio 131, 3.35 g, 73 %), m.p. ca 425°(dec.) 3 1H-NMR 3 s 1.78(s,4H), 4.10(s,4H), 4.62(s,4H), 5.30(s,4H) 3 2.02 (s,4H), 4.23(s,4H), 4.73(s,4H), 5.26(s,4H), the remaining aryl peaks were too complicated to assign to individual isomers3 they appeared as follows : 6 6.77(s), 6.82-6.93(m), 6.98-7.01(m), 7.06-7.10(m), 7.18(s), 7.19-7.35(m) 3 mass spectrum35 (retro Diels-Alder reaction), m/g (rel. intensity) 564(M+-20,4), 538(17), 380(100), 354(60), 252(3), 210(5). To a suspension of a mixture of 101 and 102 (2.75 g, 3 mmole) in ethanol (250 mL) was added slowly 15 mL of 72 % perchloric acid and the soln was heated at reflux for 8 h. Work up as for 98 gave 103 (1.14 g, 43 %) as colorless crystals, m.p. > 450°: 1H-NMR : 6 5.295(s,4H), 5.365(s,4H), 6.802-6.836(dd,4H), 6.879-6.952(m,8H), 7.213-7.331(m,12H), 7.452(s,4H), 7.689(s,4H), 7.947(s,2H) 3 13c-NMR : 6 53.442, 53.959, 119.817, 121.030, 123.502, 123.456, 125.008, 125.047, 125.542, 128.332, 130.321, 141.335, 142.936, 144.367, 145.265, 145.402 (two peaks were missing) 3 mass spectrum35, m/g (rel. intensity) 883(M+,58), 882(72),704(3), 112 446(85), 354(100), 268(25), 252(17) 3 UV(cyc1ohexane) Amax 372(6 4467), 353(5730), 335(5730), 320(5307), 296(71,372), 280(44,386), 271(50,880), 264(86,828), 261(73,747), 258 (61,317), 254(64,469), 250(53,947), 243(50,730)3 Anal. : Calcd. for C7OH42 : C, 95.213 H, 4.79. Found : C, 94.87 3 H, 5.13. 24. 5,16[1',2'JBenzeno-S,16-dihydrohexacene (108). A soln of 1,4-dihydroanthracene-1,4-epoxide33 (854 mg, 4.4 mmole) and 52 (920 mg, 4 mmole) in xylene (60 mL) was heated at reflux for 72 h. The solvent was removed (rotavap), and the residue was recrystallized from MeOH to give 106 (1.51 g, 89 %), m.p. ca 245°(dec.) 3 1H-NMR 3 6 1.98(dd,2H), 2.27(dd,2H), 2.86(dd,2H), 4.80(s,2H), 5.05 (s,2H), 6.84(dd,2H), 6.9l(dd,2H), 7.18(dd,2H), 7.23(dd,2H), 7.40(dd,2H), 7.52(s,2H), 7.73(dd,2H) 3 13c-NMR 3 6 30.37, 42.63, 55.79, 84.98, 116.86, 122.42, 122.52, 124.12, 124.26, 125.59, 128.07, 132.75, 142.84, 143.55, 146.41, 146.92 3 mass spectrum, m/g (rel. intensity) 424(M+,l), 406(2), 350(4), 253(3), 228(5), 215(7), 202(6), 178(25), 168(100), 152(4), 139(10). To a soln of 105(l.27 g, 3 mole) in acetic anhydride (100 mL) was added slowly 12 mL of cone. HCl, and the mixture was heated at reflux for 10 h. The cooled soln was poured into ice-water and extracted with methylene chloride. The extract was washed with 10 % sodium carbonate, water, and dried. Solvent removal followed by column chromatography using CH Clz-hexane (1:3) as the eluent gave a mixture of 2 113 106 and 107 (511 mg, 42 %), m.p. > 250°(dec.) 3 1H-NMR : (107) 6 2.35(dd,1H), 2.79(1H), 3.07(dd,1H), 4.38(s,1H), 4.92 (3,13), 6.64(s,lH), 7.06(dd,2H), 7.12(dd,2H), 7.37(dd,4H), 7.46(dd,2H), 7.50(s,lH), 7.55(s,lH), 7.90(dd,2H), 8.18 (s,lH), 8.21(s,lH) 3 (106) 6 3.90(s,4H), 4.95(s,2H), 6.97 (dd,4H), 7.37(dd,4H), 7.46(dd,2H), 7.76(s,2H), 7.92(dd,2H), 8.27(s,2H) 3 mass spectrum (mixture), m/g (rel. intensity) 406(M+,2), 354(4), 228(9), 212(28), 191(12), 178(46), 119 (20), 94(99), 56(63), 41(100). A soln of 106 and 107 (406 mg, 1 mmole) in mesitylene (30 mL) containing 50 mg of 10 %‘Pd/C was heated at reflux for 48 h. The hot soln was filtered and the catalyst was washed with 20 mL toluene. The combined filtrate was concentrated under reduced pressure to give 108 (372 mg, 92 %) as orange crystals, m.p. 362-364°(dec.) 3 1H-NMR 3 8 5.53(s,2H), 7.07 (dd,4H), 7.35(dd,2H), 7.46(dd,4H), 7.86(s,2H), 7.95(dd,2H), 8.46(s,2H), 8.56(s,2H) 3 13c-NMR 3 6 53.52, 121.18, 123.81, 124.98, 125.58, 125.86, 126.04, 128.20,- 130.58, 131.27, 140.60, 143.88 (one peak was missing) 3 mass spectrum, m/g (rel. intensity) 404(M+,11), 403(5), 402(4), 202(2), 201(6), 69(2), 55(2), 44(5), 33(100) 3 UV (cyclohexane) Amax 469 nm ( 6 16,363), 440(16,283), 415(15,129), 404(14,992), 392 (14,685), 382(14,517), 370(14,425), 302(81,787), 291 (72,602), 281(69,551) 3 Anal 3 Calcd. for c H : 0, 94.863 32 20 H, 5.32. Found 3 C, 94.62; H, 5.48. 25. Bis-cycloadducts of 40 and 114 (116). (a) Synéadduct A mixture of benzocyclobutene37 (5.20 g, 114 50 mmole), 4081413 (5.25 g, 25 mmole) and toluene (60 mL) in a sealed tube was heated at 185-195°for 24 h. The ppt that deposited in the cooled soln was filtered and saved. The filtrate was concentrated (rotavap) and triturated with hexane. The resulting solid was then filtered, washed with hexane and combined with the above ppt to give 1168 (8.78 g, 84 %), m.p. 238-240°3 1H-NMR 3 6 l.97(dd,4H), 2.70(dd,4H), 2.98(dd,4H), 5.06(s,2H), 7.09(bs,8H), 7.18(s,2H) 3 13c-NMR 3 6 33.11, 42.82, 84.57, 110.46, 126.15, 126.83, 138.96, 144.66 3 mass spectrum, m/g (rel. intensity) 288(10), 270(1), 158(100), 130(7), 129(11), 128(9), 115(8), 102(4), 40(51) 3 Anal 3 Calcd. for C30H26°2 3 C, 86.093 H, 6.26. Found 3 C, 85.963 H, 6.30. (b) Anti-adduct A mixture of benzocyclobutene (4.16 g, 40 almmole), 40a (4.20 g, 20 mmole) and toluene (50 mL) in a sealed tube was heated at 185-195°for 24 h. Work up as above gave 116a (7.27 g, 87 %), m.p. ca 272°(dec.) 3 1H-NMR 3 5 1.94(dd,4H), 2.69(dd,4H), 3.01(dd,4H), 5.08(s,4H),7.12 (bs,8H), 7.15(s,2H) 3 1332-30413 3 5 33.10, 42.77, 84.53, 110.70, 126.20, 126.87, 138.87, 144.66 3 mass spectrum, E/g (rel. intensity) 288(15), 270(1), 158(100), 130(7), 129(11), 128(9), 115(7), 102(6). 26. Dehydration of 116s. (a) HClO -EtOH To a suspension of 1168 (1.254 g, 3 mmole) 4 in ethanol (200 mL) was added slowly 15 mL of 72 % perchloric acid. The resulting soln was heated at reflux for 20 h. The cooled soln was poured into ice-water and the 115 ppt was filtered, washed with water and dried. The crude product was recrystallized from benzene to give a mixture of 117 and 112 (NMR ratio 4:1, 690 mg) 3 1H-NMR of 117 3 6 2.11 (dd,2H), 2.75(dd,2H), 3.04(dd,2H), 4.06(s,4H), 5.24(s,2H), 7.13(bs,4H), 7.20(dd,2H), 7.32(dd,2H), 7.57(s,2H), 7.71(s,2H). To a suspension of 1168 (1.672 g, 4 mmole) in ethanol (300 mL) was added slowly 20 mL of 72 % (perchloric acid. The soln was heated at reflux for 60 h, and worked up as above. Recrystallization of the crude product from 1,2- dichloroethane gave a mixture of 112 and 113 (NMR ratio 1:2, 1 932 mg, 61 %). H-NMR of 112 3 6 4.12(s,8H), 7.20(dd,4H), 7.33(dd,4H), 7.89(s,4H), 8.29(s,2H) 3 1H-NMR of 113 3 6 4.06 (8,43), 4.21(s,4H), 7.15-7.42(m,6H), 7.69(s,2H), 7.71(s,2H), 7.77(s,2H), 7.78(dd,2H) 3 mass spectrum (mixture of 112 and 113), m/g (rel. intensity) 382(M+,1), 280(6), 165(4), 149(5), 139(6), 108(8), 99(100), 55(46). (b) HCleAc 0 To a suspension of 1163 (1.254 g, 3 mmole) 2 in acetic anhydride (70 mL) was added slowly 14 mL of cone. hydrochloric acid through the condenser. The mixture was heated at reflux for 12 h. The cooled soln was poured into cold 10 % sodium carbonate (400 mL) and the ppt filtered, washed with water, ethanol and dried. Recrystallization of the crude product from benzene gave a mixture of 112 and 113 1H NMR spectrum was similar to that (619 mg, 54 %). The shown above. (c) HC104—HBOH-toluene To a suspension of 1163 (2.09 g, 5 mmole) ‘in methanol (30 mL) and toluene (120 mL) was added 116 slowly 15 mL of 72 % perchloric acid. The soln was then heated at reflux for 16 h. The resulting ppt in the cooled soln was filtered, washed with water, methanol and dried. Recrystallization from 1,2-dichloroethane gave a mixture of 112 and 113 (1.34 g, 70 %). 27. Attemped cycloaddition of 50 with 112. A soln of 50 (485 mg, 2.5 mmole) and a mixture of 112 and 113 (obtained from dehydration of 116, 955 mg, 2.5 mmole) in xylene (120 mL) was heated at reflux for 3 days. The solvent was evaporated (rotavap). Column chromatography of the residue over silica gel using CHZClz-hexane (1:3) as 1 eluent gave 113 (760 mg) and 50 (370 mg). H NMR of 113 was identical to that shown above. 28. Bis-cycloadducts of 40a and 119 (120). 39 A soln of 1,2-bis-methylenecyclohexane 119 (1.08 g, 10 14b (1.05 g, 5 mmole) in dioxane (80 mL) was mmole) and 40a heated at reflux for 14 h. The solid that deposited in the cooled soln was filtered, washed with a small amount of dioxane and dried to give 120 (682 mg, 32 %) as colorless crystals, m.p. > 278°(dec.) 3 1H-NMR 3 6 1.57(m,8H), 1.82 (m,4H), 1.93(m,8H), 2.12(m,8H), 4.90(s,4H), 7.04(s,2H) 3 13C-NMR : 6 23.28, 29.94, 33.17, 42.35, 84.76, 110.31, 129.96, 144.66 3 mass spectrum, m/g (rel intensity) 292(21), 274(4), 158(100), 91(13) 3 Ana; 3 Calcd. for C3OH34O2 3 C, 84.473 H, 8.03. Found 3 0, 83.983 H, 7.87. 117 29. Tetracene (15). A mixture of benzocyclobutene (1.04 g, 10 mmole), 1,4- dihydronaphthalene-l,4-epoxide33 (1.44 g, 10 mmole) and toluene (45 mL) in a sealed tube was heated at 190°for 24 h. Work up as for 1163 gave 122 (2.13 g, 86 %) as colorless crystals, m.p. 161-163°3 1H-NMR: 6 2.02(dd,2H), 2.74(dd,2H), 3.04(dd,2H), 5.13(s,2H), 7.12(bs,4H), 7.14(dd,2H), 7.24 (dd,2H) 3 13c-NMR 3 6 33.07, 42.84, 84.57, 118.90, 126.17, 126.55, 126.84, 138.93, 145.62 3 mass spectrum, m/g (rel. intensity) 248(M+,1), 128(6), 118(100), 90(5). To a soln of 122 (1.86 g, 7.5 mmole) in acetic anhydride (40 mL) was added slowly 8 mL of conc. hydrochloric acid through the condenser. The soln was heated at reflux for 8 h. The cooled soln was poured into ice-water, and the ppt was filtered, washed with water, methanol and dried. The crude product was recrystallized from toluene to give 125 (1.54 g, 89 2), m.p. 207-208 (lit.46 209-210) 3 1H-NMR 3 4.09 (s,4H), 7.21(dd,2H), 7.34(dd,2H), 7.41(dd,2H), 7.76(s,2H), 7.78(dd,2H) 3 mass spectrum, m/g (rel. intensity) 230 (M+,100), 229(97), 228(74), 226(18), 215(10), 202(5), 114 (54), 107(16), 101(22), 88(7). A soln of 125 (1.15 g, 5 mmole) in xylene (30 mL) containing 150 mg 10 % Pd/C under argon atmosphere was heated at reflux for 2 days. The hot soln was filtered to remove the catalyst. Solvent removal (rotavap) gave tetracene 15 (1.08 g, 95 %) as orange crystals, m.p. 339-341o (Lit.47 340-3417) 3 1H-NMR 3 6 7.40(dd,4H), 8.00 (dd,4H), 8.67(s,4H). 118 30. 2,3-Dibro-otetracene (127). A mixture of benzocyclobutene (1.04 g, 10 mmole), 38 (3.02 g, 10 mmole) and toluene (60 mL) in a sealed tube was heated at 190° for 24 h. Work up as for 1163 yielded 123 (3.61 g, 89 %) as colorless crystals, m.p. 179-1819(CH2C12- hexane) 3 lH-NMR 3 6 1.99(dd,2H), 2.70(dd,2H), 2.98(dd,2H), 5.07(s,2H), 7.13(bs,4H), 7.49(s,2H) 3 13c-NMR 3 632.75, 42.47, 83.96, 122.32, 124.38, 126.35, 126.90, 138.35, 146.65 3 mass spectrum, m/g (rel. intensity) 278(62), 276(100), 274(55), 248(1), 195(5), 169(10), 167(8), 128(18), 115(13). To a soln of 123 (2.84 g, 7 mmole) in acetic anhydride (70 mL) was added slowly 15 mL of cone. hydrochloric acid through condenser. The soln was then heated at reflux for 8 hour. Work up as for 125 gave 126 (2.44 g, 90 %) as light yellow crystals, m.p. 224-226°(toluene) 3 1H-NMR 3 6 4.06 (s,4H), 7.22(dd,2H), 7.34(dd,2H), 7.63(s,2H), 8.07(s,2H) 3 13c-NMR : 6 36.78, 124.11, 126.49, 127.27, 131.54, 132.07, 136.44, 137.46, 137.77 3 mass spectrum, m/g (rel. intensity) 390(M+4,65), 388(M+2,100), 386(M+,55), 309(39), 307(42), 228(87), 226(74), 114(38), 113(34). A soln of 126 (1.16 g, 3 mmole) in xylene (50 mL)' containing 150 mg 10 % Pd/C under argon was heated at reflux for 2 days. The hot soln was filtered to remove the catalyst. Solvent removal (rotavap) gave 2,3-dibromo- tetracene 127 (1.10 g, 96 %) as orange crystals, m.p. 336- 338°. It was too insoluble to obtain an NMR spectrum. Mass spectrum, m/g (rel. intensity) 388(M+4,4), 386(M+2), 384 119 (M+,4), 308(4), 306(4), 228(9), 226(13), 113(10), 33(100). Anal 3 Calcd. for C H Br 18 10 2 3 C, 55.603 H, 2.61. Found 3 C, 55.26; H, 2.78. 31. Pentacene (10). A mixture of benzocyclobutene (2.08 g, 20 mmole), 50 (3.88 g, 20 mmole) and toluene (70 mL) in a sealed tube was heated at 190 for 24 h. Work up as for 1163 gave 124 (5.18 g, 87 3), m.p. 235-237 (toluene) 3 lH-NMR 3 6 2.12(dd,2H), 2.78 (dd,2H), 3.04(dd,2H), 5.25(s,2H), 7.13(bs,4H), 7.44(dd,2H), 7.62(s,2H), 7.79(dd,2H) 3 13c-NMR 3 6 32.89, 43.50, 84.55, 117.13, 125.69, 126.25, 126.90, 128.12, 132.82, 138.69, 143.67 3 mass spectrum, m/g (rel. intensity) 298(M+,1), 168 (100), 140(5), 129(3), 91(7). To a soln of 124 (2.98 g, 10 mmole) in methanol (40 mL) and toluene (160 mL) was added slowly 15 mL of conc. HCl. The soln was heated at reflux for 14 h. The resulting solid in the cooled soln was filtered, washed with> methanol and dried. Recrystallization of the crude product from 1,2- dichloroethane gave 128 (2.07 g, 74 %) as yellowish crystals, m.p. 305-307°(lit.48 300-310°) 3 1H-NMR 3 6 4.13 (s,4H), 7.20-7.44(m,6H), 7.92(s,2H), 7.98(dd,2H), 8.36(s,2H) 3 mass spectrum, m/g (rel. intensity) 280(M+,100), 279(73), 278(49), 265(6), 139(9), 133(6), 91(33), 81(14). A soln of 128 (560 mg, 2 mmole) in xylene (20 mL) containing 80 mg of 10 % Pd/C under argon was heated at reflux for 3 days. The hot soln was carefully filtered to remove the catalyst. The red purple filtrate was quickly 120 concentrated (rotavap) to give pentacene (512 mg, 92 %) as violet blue crystals. The spectra (IR, UV and mass) were identical to those of a commercial sample. 32. 7,16[1',2']Benzeno-7,16-dihydroheptacene (109). A soln of 128 (1.40 g, 5 mmole) and 50 (0.97 g, 5 mmole) in xylene (160 mL) was heated at reflux for 5 days. The solid that deposited in the cooled soln was filtered as unreacted 128 (0.21 g). The filtrate was concentrated (rotavap). Column chromatography of the residue using CHZClz-hexane (133) as the eluent gave a mixture of 135 and 136 (1.49 g, 63 %), m.p. 294-296 3 1H-NMR 3 (135) 2.35 (s,2H), 3.82(s,4H), 4.46(s,2H), 5.06(s,2H), 7.13(dd,2H), 7.18(s,2H), 7.20-7.3l(m,6H), 7.39(dd,2H), 7.49(s,2H), 7.72 (dd,2H) 3 (136) 2.32(s,2H), 3.91(dd,4H, AB type), 4.45 (s,2H), 5.07(s,2H), 6.99(dd,2H), 7.15-7.30(m,8H), 7.39 (dd,2H), 7.50(s,2H), 7.72(dd,2H) 3 mass spectrum, m/g (rel. intensity) 474(M+,9), 456(4), 388(6), 374(4), 305(9), 293(46), 280(16), 278(19), 207(21), 194(26), 181(67), 168 (56), 139(13), 44(100). To a mixture of 135 and 136 (1.422 g, 3 mmole) in acetic anhydride (60 mL) was added slowly 12 mL of conc. HCl through condenser. The soln was heated at reflux for 12 h. The cooled mixture was poured into ice-water, and extracted with methylene chloride. The extract was washed with 10 % sodium carbonate, water and dried. Solvent removal (rotavap) followed by column chromatography using CHZClz- hexane (134) as the eluent gave 137 (656 mg, 48 %), m.p. 121 >205°(dec.) 3 1H-NMR: 6 3.84(s,4H), 5.52(s,2H), 7.03(dd,2H), 7.1l(dd,2H), 7.21(dd,2H), 7.36-7.43(m,6H), 7.87(s,2H), 7.93 (dd,2H). A soln of 137 (547 mg, 1.2 mmole) in mesitylene (20 mL) containing 80 mg of 10 % Pd/C was heated at reflux for 60 h. The hot soln was filtered to remove the catalyst. Solvent removal by reduced pressure distillation gave 109 (528 mg, 97 %) as light yellowish crystals, m.p. > 360°(dec.) 3 1H- NMR 3 6 5.68(s,2H), 7.11(dd,2H), 7.41(dd,4H), 7.52(dd,2H), 7.93(dd,4H), 7.98(s,4H), 8.28(s,4H) 3 13c-NMR 3 6 53.30, 121.66, 123.95, 125.02, 125.72, 126.24, 127.99, 130.69, 131.71, 140.35, 143.35 3 mass spectrum, m/g (rel. intensity) 454(M+,59), 453(35), 452(24), 290(4), 274(13), 227(100), 226 (97), 213(34), 197(11), 165(6), 149(6), 105(5) 3 UV (cyclohexane) Amax 378 nm ( 6 14,298), 353(14,430), 342 (14,361), 325(14,217), 283(31,700), 254(20,762), 212(15,070). Anal 3 Calcd. for c H 3 c, 95.123 H, 4.88. 36 22 Found 3 C, 94.873 H, 5.04. 33. Benzyne adduct of 109 (27). A mixture of 109 (227 mg, 0.5 mmole), benzenediazonium-z- carboxylate hydrochloride (222 mg, 1.2 mmole) and propylene oxide (2 mL) in 20 mL of 1,2-dichloroethane was heated at reflux for 5 h. Work up as for 24 gave 27 (152 mg, 50 %). 1 The H NMR spectrum was identical to that of independently synthesized 27 14b. 122 34. 6315(1'32']Benzeno-2,3-dibrono—6,15—dihydrohexacene (143). A soln of 128 (1.40 g, 5 mmole) and 38 (1.51 g, 5 mmole) in xylene (200 mL) was heated at reflux for 5 days. The solid that deposited in the cooled soln was filtered) as 6,13-dihydropentacene (284 mg, rearranged from 128), m.p. 269-271.°(lit.49 270-271’) 3 1H-NMR (not previously recorded) 3 6 4.25(s,4H), 7.42(dd,4H), 7.79(dd,4H), 7.80(s,4H). The filtrate was concentrated (rotavap). Column chromatography of the residue using CHZClz-hexane (133) as the eluent gave a mixture of 140 and 141 (ratio 831, 1.37 g, 47 %), m.p. > 220°(dec.) 3 1H-NHR 3 (140) 6 2.14(s,2H), 3.85(s,4H), 4.35 (s,2H), 4.85(s,2H), 7.15(dd,2H), 7.17(dd,2H), 7.18(s,2H), 7.24(m,4H), 7.38(s,2H) 3 (141) 6 2.24(s,2H), 3.91(dd,4H, AB type splitting),4.38(s,2H), 4.91(s,2H), 7.01(dd,2H), 7.14 (dd,2H), 7.21(s,2H), 7.22(m,4H), 7.40(s,2H) 3 mass spectrum, m/s (rel. intensity) 584(M+4,6), 582(M+2,24), 580(M+,15), 564(3), 502(1), 305(29), 293(78), 280(77), 278(100), 276(37), 274(12), 265(9), 195(15), 114(11). A soln of 140 (1.164 g, 2 mmole) in xylene (150 mL) containing 150 mg of 10 % Pd/C was heated at reflux for 3 days. The hot soln was filtered to remove the catalyst. Solvent removal (rotavap) gave 142 (1.08 g, 93 %), m.p. ca 228°(dec.) 3 1H-NMR 3 6 2.35(s,2H), 4.57(s,2H), 5.00 (s,2H), 7.l9(dd,2H), , 7.34(dd,2H), 7.41(dd,2H), 7.42(s,2H), 7.77 (s,2H), 7.94(dd,2H), 8.27(s,2H) 3 13c-NMR 3 6 47.23, 47.62, 81.12, 121.37, 124.07, 124.21, 125.06, 125.69, 126.66, 126.90, 128.00, 130.91, 131.61, 140.34, 140.63, 147.57 3 123 spectrum, m/g (rel. intensity) 582(M+4,7), 580(M+2,17), 578 (M+,12), 562(5), 500(1), 304(32), 302(47), 291(22), 280(44), 278(100), 276(27), 274(12), 195(27), 193(31), 139(19), 126 (28), 114(27). To a soln of 142 (928 mg, 1.6 mmole) in acetic acid (60 mL) was added slowly 8 mL conc. sulfuric acid. The mixture was heated at reflux for 8 h. The cooled soln was poured into ice-water and extracted with methylene chloride. The extract was washed with 10 % sodium carbonate,‘ water and dried. Evaporation of the solvent followed by column chromatography using CHZClz-hexane (134) as the eluent gave 143 (387 mg, 43 %), m.p. > 230°(dec.) 3 1H-NMR 3 6 5.64 (s,2H), 7.11(dd,2H), 7.40(dd,2H), 7.50(dd,2H), 7.67(s,2H), 7.92(dd,2H), 7.94(s,2H), 7.96(s,2H), 8.27(s,2H) 3 13c-NMR 3 5 53.27, 120.76, 121.44, 121.76, 124.04, 125.16, 125.76, 126.27, 127.99, 130.52, 131.68, 131.80, 139.86, 142.62, 143.16 3 mass spectrum, m/g (rel. intensity) 564(M+4,9), 562 (M+2,22), 560(M+,12), 482(4), 480(5), 402(5), 400(8), 201(8), 200(10), 44(100). 35. Benzyne adduct of 143 (78). A mixture of 143 (168.6 mg, 0.3 mmole), benzenediazonium- 2-carboxylate hydrochloride (56 mg, 0.3 mmole) and propylene oxide (2 mL) in 15 mL of 1,2-dich1oroethane was heated at reflux for 3 h. Work up as for 24 gave 78 (117 mg, 61 %). 1 The H NMR was identical to that of independently synthesized 78. 124 36. Photodimer of [3(b,b)b.1.1]triptycene (139). Triptycene 20 (10 mg) was dissolved in 0.5 mL benzene-d6, placed in a 5 mm NMR- tube and flushed with argon. Irradiation of the sample for 90 minutes using a Hanovia 450 W medium pressure lamp with a Pyrex filter was carried out by taping the sample tube directly to the water-cooled jacket of the lamp. After irradiation, the sample tube was immediately transfered to the Bruker WM 250 NMR spectrometer, and the spectrum was recorded. 1H-NMR (benzene-d6) 3 6 4.27(s,4H), 5.12(s,4H), 6.17(dd,4H), 6.60(dd,4H), 6.84(s,4H), 6.85 (dd,4H), 6.95(dd,4H), 6.98(dd,4H), 7.21(dd,4H). A larger scale reaction (20, 354 mg) was carried out using a Pyrex test tube instead of the NMR tube, in dry benzene (15 mL). After irradiation for 3 hour as described above, the resulting ppt was filtered, washed with benzene and dried to give 139 (219 mg, 62 %) as a colorless powder, m.p. 281-283o, sparingly soluble in organic solvents. Mass spectrum (thermal reversal to 20), m/g (rel. intensity) 354 (100), 353(70), 352(57), 276(3), 176(45). Anal 3 Calcd. for C56H36 3 0, 94.883 H, 5.12. Found 3 c, 94.69, H, 5.23. 37. Bisadducts of 40 and 153 (1,438,11-dicarbonyl-5,1437,12- diepoxy-1,2,3,4,8,9,10,11-octaphenyl-1,4,4a,5,7,7a,8,11- 12,14,14a-didecahydropentacene)(160). (a) Syn-adduct A mixture of 40s (1.05 g, 5 mmole) and tetraphenylcyclopentadienone 153 (3.84 g, 10 mmole) in benzene (80 mL) was heated at reflux for 12 h until the 125 purple color disappeared. The solvent was evaporated (rotavap). The residue was triturated with methanol to give a colorless ppt. The solid was filtered, washed with methanol and dried to yield 1608 (4.40 g, 90 %) as a colorless powder, m.p. > 240°(dec.) 3 1H-NMR 3 6 3.16(s,4H), 5.81(s,4H), 6.87-6.99 (m,20H), 7.26-7.47(m,22H). (b) Anti-adduct In a similar experiment, 40a (2.10 g, 10 mmole), 153 (7.68 g, 20 mmole) and benzene (180 mL) gave 160a (8.99 g, 92 %) as a colorless powder, m.p. ca 2800 (dec.) 3 1H-NMR 3.53.06(s,4H), 5.84(s,4H), 6.87-7.04(m,20H), 7.27-7.52(m,20H), 7.58(s,2H) 3 IR (nujol) 1775, 1470, 1380 cm_1. Ana; 3 Calcd. for C72H5004 3 C, 88.323 H, 5.15. Found 3 C, 88.313 H, 4.87. 38. Reaction of 160a with dimethyl acetylenedicarboxylate (162). A mixture of 160a (1.956 g, 2 mmole), dimethyl acetylene- dicarboxylate (568 mg, 4 mmole) and xylene (60 mL) was heated in a sealed tube at 170°for 13 h. The solvent was evaporated (rotavap). Column chromatography of the residue on flash silica gel using benzene-chloroform (131) as the eluent gave tetraphenylbenzene (1.47 g, 96 %). Further elution with EtOAc then gave 162 (681 mg, 77 %) as a mixture of syn and anti adducts, m.p. 276-278°(dec.) from EtOAc 3 1H-NMR 3 (anti) 6 3.81(s,12H), 5.9l(s,4H), 7.53(s,2H) 3 (syn) 6 3.81(s,12H), 5.91(s,4H), 7.49(s,2H) 3 13c-NMR 3 (anti) 6 52.45, 84.85, 115.90, 146.37, 151.55, 162.69 3 mass spectrum, m/s (rel. intensity) 442(M+,7), 382(5), 353(10), 335(44), 334(29), 322(71), 300(42), 295(17), 268(14), 240 126 (100), 228(30), 211(16), 158(20) 3 IR (nujol) 1730, 1710, 1460, 1440, 1310, 1280, 1230, 1115, 970, 860 cm'1 3 Anal 3 Calcd. for C22H18010 3 C, 59.733 H, 4.10. Found 3 C, 59.703 H, 4.06. 39. Reaction of 160a with tetracyanoethylene (163). In a similar experiment to 162, a sealed tube was charged with 160a (1.956 g, 2 mmole), tetracyanoethylene (512 mg, 4 mmole) and xylene (60 mL). The ppt that deposited in the cooled soln was filtered, washed with benzene and dried to give 163 (803 mg, 97 %) as tan crystals, m.p. > 205°(dec) 3 1H-NMR (onso-dé) 3 6 6.93(s,4H), 7.98(s,2H) 3'13c-NMR (unso- ° 6 49.38, 87.73, 110.28, 112.28, 119.30, 140.80. d6) . 40. Reaction of 160a with naphthaquinone (164). In a similar experiment to 162, a sealed tube was charged with 160a (1.956 g, 2 mmole), naphthaquinone (632 mg, 4 mmole) and xylene (60 mL). Work up as for 162 gave tetra- phenylbenzene (1.44 g, 94 %) and 164 (711 mg, 75 %). M.p. of 164 3 > 320°(dec.) 3 1H-NMR 3 6 3.05(s,4H), 5.84(s,4H), 7.55(s,2H), 7.81(dd,4H), 8.17(dd,4H) 3 mass spectrum (rel. intensity), m/s 474(M+,2), 316(2), 278(40), 158(100), 130 (14), 125(12) 3 IR (nujol) 1680, 1595, 1470, 1380, 1275 cm"1 3 Anal 3 Calcd. for C30H1806 3 C, 75.943 H, 3.82. Found 3 C, 76.073 H, 3.97. 41. Reaction of 160a with 1,4-anthraquinone (165). In a similar experiment to 162, a sealed tube was charged 127 with 160a (1.956 g, 2 mmole), 1,4-anthraquinone (832 mg, 4 mmole) and xylene (60 mL). The ppt that deposited in the cooled soln was filtered, washed with benzene and dried to give 165 (918 mg, 80 %) as a light yellow solid, m.p. 326- 328’(dec.) 3 lH-NMR 3 6 3.95(q,4H), 5.92(q,4H), 7.07(s,2H), 7.71(dd,4H), 8.07(dd,4H), 8.55(s,4H) 3 mass spectrum (retro Diels-Alder fragment), n/g (rel. intensity) 366(M+- anthraquinone,1) 208(anthraquinone,32), 158(100), 152(29), 126(32) 3 IR (nujol) 1680, 1620, 1580, 1465, 1380, 1270, 1195, 975, 860, 760 cm'l. 42. Reaction of 160a with 1,4-dihydronaphthalene-1,4-epoxide (166). In a similar experiment to 162, a sealed tube was charged with 160a (1.956 g, 2 mmole), 1,4-dihydronaphtha1ene-1,4- epoxide33 (576 mg, 4 mmole) and xylene (60 mL). Work up was as described for 162. Column chromatography using benzene- chloroform (131) and then chloroform as eluents gave tetra- phenylbenzene (1.39 g, 91 %) and 166 (651 mg, 73 %). M.p. of 166 3 306-308°(dec.) 3 1H-NMR 3 6 2.77(q,4H), 4.68(s,4H), 5.32(q,4H)3 2.90(q,4H), 4.78(s,4H), 5.44(q,4H), 7.02- 7.26(m,10H) 3 mass spectrum, n/g (rel. intensity) 446(M+,1), 428(1), 302(62), 273(17), 184(21), 158(100), 131(31), 118 (61) 3 Ann; 3 Calcd. for C30H2204 3 C, 80.703 H, 4.97. Found 3 0, 80.483 H, 5.04. 43. 5,1839,14-Heptacenediquinone (161). To a suspension of 164 (474 mg, 1 mmole) in acetic acid 128 (30 mL) was added 4 mL of conc. sulfuric acid and the mixture was heated at reflux for overnight. The cooled soln was poured into ice-water. The resulting ppt was filtered, washed with water, methanol and dried to give 161 (394 mg, 90 %). m.p. > 350°(nitrobenzene) 3 owing to the insufficient solubility in all solvents tried, no NMR spectrum was 67 showed 11* at m/s 438 3 IR (nujol) 1680, 1590, 1285, 890 cm-1. The quinone gave a dark recorded 3 the mass spectrum green solution in conc. sulfuric acid. It also gave a brownish-orange vat dye with alkaline sodium dithionite66. 44. 6,21310,17-NOnacenediquinone (171). In a similar experiment to 161, a mixture of 165 (574 mg, 1 mmole), acetic acid (40 mL) and conc. sulfuric acid (5 mL) was heated at reflux overnight. Work up as for 161 gave 171 (495 mg, 92 %) as golden needles from nitrobenzene, m.p. > 360 3 this compound was too insoluble to record an NMR 67 spectrum 3 the mass spectrum showed M+ at n/g 538 3 IR (nujol) 1670, 1610, 1595, 1280, 995 cm-1. In conc. sulfuric acid it showed a dark green solution. Ann; 3 Calcd. for C38H1804 : C, 84.75, H, 3.37. Found 3 C, 84.58, H, 3.49. 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N e a 3 m 3 414.4 4 3 3 J). 33...“)32/3.) 1338.31.33.13}. lllljsn)‘ 1.14.. 145R. .\\\||3 3.3. :13 13 s is? ._ \k .I\ 144 .AMOHV osmooompcsouoxzmuOOIom.v~.o~.mH.MH.HH.h.mIocmucmnouuoo 3H==~.==H1ms.msu_Em.se_o~.aeuH=~.=H_v~.eum.~..Heo~.mneus< e0 mzz : Hz: omm .os H l. 31,313 M,“ T i x, 1,4. 3.3 .3 4, _ 3 :03 l \ 145 .xooev osmooudmsouc>secsos.suocmncmmfl.N..Heoe.e Mo «22 ms was one .5” c H N n v m M h M o V'—r*'l’Prrr’l—VP?r-?rL'r”_r’?rr—”"P’V’r—'Pr¥Pr’Pr3—'rrrp”r’ Ptrp”*+—"??Pr’}’ JHIJJW . J? 1 l \3 rr'rp’ Prr— r?’*PF . Ame: osmowxonouo>zHounH.wuosouanum.mnocoucomH.m..Hgmfi.o mo «:2 :H mm: omm .mH o m o p a L: 5 if _Iotp L133)... ? lb p > P r_ F p p b ; APIL>II3r|3¥|;..._.I.>Ic>l flip, M: a 3 .33 p L F P p > P h _ L r L < 3. z. .\. \ 146 BIBLIOGRAPHY 147 BIBLIOGRAPHY 1. CA nomenclature is 9,10[1',2']-benzenoanthracene. 2. Bartlett, P. D.3 Ryan, M. J.3 Cohen, S.G. J. Am. Che SOC. 1942, 64, 2649. 3. Wittig, G.3 Ludwig, R. Angew. Chem. 1956, 68, 40. 4. (a) Stiles, M.3 Miller, R. G. J. Am. Chem. Soc. 1960, 8;, 3802 (b) Stiles, M.3 Miller, R. G.3 Burckhardt, U. Ibid. 1963, 85, 1792 (c) Friedman, L.3 Logullo, F. Ibid. 1963, 85, 1549 (d) Friedman, L.3 Logullo, F. J. Org. Chem. 1969, 34, 3087. 5. For a review, see Skvarchenko, V. R.3 Shalaev, V. M. M. K.3 Klabunovskii, E. I. Russ. Chem. Rev. (Engl. Transl.) 1974, 43, 951. 6. (a) Bartlett, P. D.3 Lewis, E. S. J. Am. Chem, 1950, 72 _I 19543 153 Liebigs Annln Chem. 1962, 60, 23 (d) Theilacker, Soc. 1005 (b) Bartlett, P. D.3 Greene, F. D. Ibid, 1088 (c) Wittig, G.3 Tochtermann, W. Justus W.3 Beyer, K.-H. Chem. Be;. 1961, 23, 2968 (e) Streitwieser, A. Jr.3 Caldwell, R. A.3 Granger, M. J. Am. Chem. 1964, 86, 3578. 7. (a) Nakazawa, T.3 Murata, I. J. Am. Chem. Soc. 1977, Soc. 223 1996 (b) Iwamura, H.3 Makino, K. J. Chem. Soc. Chem. Commu. 1980, 72 (c) Yamamura, K.3 Nakazawa, T.3 Murata, I. Angew. Chem. Int. Ed. Engl. 1980, l2, 543 (d) Murata, I. Pure Appl. Chem. 1983, 55, 323. 8. 10. 11. 12. 13. 14. 15. 16. 17. 148 Oki, M. Topics in Stereochemistry (Edited by Allinger, N. L.3 Wilen, S. H.) 1983, v.14, p.1 , Willey, New York. (a) Guenzi, A.3 Johnson, C. A.3 Cozzi, F.3 Mislow, K. J; Am Chem. Soc. 1983, l05, 1438 (b) Kawada, Y.3 Iwamura, H. Ibid. 1983, l 5, 1449 (c) Kawada, Y.3 Iwamura, H.3 Okamoto, Y.3 Yuki, H. Tetrahedron Lett. 1983, 25, 791 (d) Koga, N.3 Iwamura, H. J. Am. Chem. Soc. 1985, 107, 1426. Wittig, G.3 Harle, H.3 Knauss, E.3 Niethammer, K. gneng §§£1 1960, 23, 951. (a) Sugihashi, M.3 Kawagita, R.3 Otsubo, T.3 Sakata, Y.3 Misumi, S. Bull. Chen. Soc. Japan 1972, 25, 2836 (b) Hayashi, T.3 Mataga, N.3 Misumi, S. Inigg 1975, eg, 416. Hosoda, Y. Sengyo Kogaku 1957, 556. Gihodo, Tokyo. This reference is unavailable to us. (a) Zimmerman, H. E.3 Amick, D. R. J. Am. Chem. Soc. 1973, g5, 3977 (b) Hayes, P. C.3 Paquette, L. A. J. Org. Chem; 1983, 48, 1257. (a) Hart, H.3 Shamouilian, S.3 Takehira, Y. J. Org. gneng 1981, £53 4427 (b) Hart, H.3 Raju, N.3 Meador, M. A.3 Ward, D. L. g. Ogg, Chem. 1983, 48, 4357. Skvarchenko, V. R.3 Shalaev, V. K. Dokl. Akad. Nauk SSSR, Ser. Khim. (Engl. Transl.) 1974, ;_§, 307. Cadogan, J. I. G.3 Harger, M. J. P.3 Sharp, J. T. J; Chem. Soc. B 1971, 602. (a) Hart, H.3 Lai, C-Y; Nwokogu, G.3 Shamouilian, S.3 Teuerstein, A.3 Zlotogorski, C. Je_Ane_Qneng__§ggg 1980, 02, 6649 (b) Hart, H.3 Nwokogu, G. J. Org. Chem. 1981, 18. 19. 20. 21. 149 6, 1251 (c) Hart, H.3 Nwokogu, G. Tetrahedron Lett. 1983, 24, 5721. Meador, M. A. Ph. D. Thesis, Michigan State University, 1983. Hart, H.3 Bashir-Hashemi, A.3 Luo, J.3 Meador, M. A. Tetgahedron 1986, 3;, 1641. Some structurally related triptycene quinones are known: (a) Clar, E. Chen, Beg, 1931, 543 1676 (b) Theilacker, W.3 Berger-Bose, U.3 Beyer, K.-H. Inigg 1960, 91,1658 (c) Yates, P.3 Eaton, P. J. Amee Chem. Soc. 1960, eg, 4436 (d) Balandin, A. A.3 Klabunovskii, E. I.3 Mamedzade, R. Y.3 Antik, L. V.3 Golelik, M. V. 13!; Akad. Nauk SSSR. Ser. Knim. (Engl, Transl.) 1966, 1651 (e) Mamedzade, R. Y.3 Klabunovskii, E. I.3 Antik, L. V.3 Balandin, A. A.3 Gorelik, M. V. 191g; 1967, 293 (f) Antik, L. V.3 Mamedzade, R. Y.3 Klabunovskii, E. I.3, Balandin, A. A. Ibid. 1967, 548 (g) Russell, G. A.3 Suleman, N. K.3 Iwamura, H.3 Webster, 0. W. J. Am. Cheng See; 1981, l_;, 1560 (h) Lipczynska-Kochany, E.3 Iwamura, H. Chem. Lett. 1982, 1075 (i) Webster, 0. W. Seminar, Michigan State University, 1984, 25 Oct.3 work done at the Central Research and Development Department, E. I. duPont de Nemous and Company, Wilmington, Delaware. Unpublished results. X-ray structure of triptycene and some simple derivatives have been determined 3 (a) Anzenhofer, K.3 deBoer, J. J. 2. Krist= 1970, 131, 103 (b) Hazell, R. G. 3 Paweley, G. 8.3 Lund-Peterson, C. E. J. Cryst. Mol. 22. 23. 24. 25. 150 Struct. 1971, l, 319 (c) Palmer, K. J.3 Templeton, D. H. gene ngse. 1968, gg4, 1048 (d) Karle, I. L.3 Estlin, J. A. z, Krist. 1969, _ee, 371 (e) Sakabe, K.3 Ozeki- Minakata, K.3 Tanaka, J. Acta Cryst. 1972, nee, 3441 (f) MacIntyre, W. M.3 Tench, A. H. J. Ogg. Chem, 1973, eg, 130. (a) Mikitaev, A. K.3 Korshak, V. V.3 Gurdaliev, Kh. Kh.; Pryadko, V. N.3 Belousov, V. N.3 Kalmykov, K. V. neglL Akad. Nank SSSR (Engl. Transl.) 1983, ;_2, 85 (b) Cassidy, P. F. " Thermally Stable Polymers 3 Synthesis and Properties ", Marcel Dekker, Inc., New York, 1980 (c) Critchley, J. P.3 Knight, G. J.3 Wright, W. W. " Heat-Resistant Polymers 3 Technologically Useful Materials " Plenum Press, New York, 1983. Some transition metal complexes of triptycene are known: (a) Pohl, R. L.3 Willeford, B. R. J. O a om t. C em. 1970, 2;, »C45 (b) Moser, G. A.3 Rausch, M. D. gyn4 Reaet. Inorg. Me .-Orq. Chene 1974, 4, 37 (c) Gancarz, R. A.3 Blount, J. F.3 Mislow, K. Organometallics 1985, 4, 2028. (a) Scheufelen, A. Justus Liebigs Annln Chem. 1885, 3313 152 (b) Cox, 3.; Kubler, D. G.3 Wilson, C. A. J. Chem. Educ. 1977, 54, 379. (a) Kenner, J.3 Ritchie, W. H.3 Wain, R. L. J. Chem. Soc. 1937, 1526 (b) Hodgson, H. H.3 (Hathaway, D. E. Ibid. 1945, 841 (c) Pearson, B. D. Chem. Ind. 1960, 899 (d) Danish, A. A.3 Silerman, M.3 Tajima, Y. A. J. Am. Chem. Soc. 1954, 76, 6144 (e) LeHouillier, C. 8.3 26. 27. 28. 29. 30. 31. 32. 33. 34. 151 Gribble, G. W. J. Org. Chem. 1983, 44, 2364. (a) Meak, J. S.3 Stacy, R. C. J. Orq. Chem. 1961, ee, 300 (b) Butler, D. N.3 Snow, R. A. Can. J. Chem. 1972, _Q, 795. Johnson, G. C.3 Bergman, R. G. Tetgahedron Lett. 1979, en, 2093 3 footnote 4. Purchased from Aldrich Chemical Company as cis/trans mixture. The low valent metal-catalyzed deoxygenation has been described : (a) Wong, H. N. C.3 Ng, T.-K.3 Wong, T.-Y. Hegegeycles 1983, eg, 1815 (b) Xing, Y. D.3 Huang, N. Z. J. Org. Chem. 1982, 41, 140 (c) Huang, N. 2.3 Xing, Y. D.3 Ye, D. Y. Synthesis 1982, 1041 (d) Shuttleworth, R. G.3 Rapson, W. 8.3 Stewart, E.-T. J. Chem. Sec, 1944, 71 (e) Hart, H.3 Nwokogu, c. J. Orq.AChen4 1981, 44, 1251. (a) Wittig, G.3 Reuther, W. Justus Liebigs Ann Chen. 1972, 1_;, 20 (b) Takeshita, H.3 Mori, A.3 Sano, S.3 Fujise, Y. Bul . Chem. Soc. Ja an 1975, 4e, 1661. This method was first developed by Bashir-Hashemi, A., which was then optimized and scaled up by author. 11a m.p. of 287-288'appears to be in error The literature since we get the identical m.p. 221-222' via four independent synthesis of 20. (a) Fieser, L. F.3 Haddadin, M. J. Can. J. Chem. 1965, 4;, 1604 (b) Matsuda, T.3 Mitsuyasu, T. Bull. Chem. Soc. Japan 1966, 42, 1342. 14a The literature was recorded at 60 MHz3 we report here the spectrum at 250 MHz. 35. 36. 37. 38. 39. 40. 41. 42. 152 Recorded on a Hitachi M-80A spectrometer at Ube Industries, Japan with following conditions : (EI) ion accelerating voltage 3000 V, ionization voltage 70 eV, total emission current 100 A, ion source temp. 1803 direct inlet temp. 300-400'C. (a) Clar, E. Qnen;__fie;; 1942, 1;, 1330 (b) Clar, E.3 Boggiano, B. J, Qnen, see, 1957, 2683. (a) Markgraf, J. H.3 Basta, S. J.3 Wage, P. M. J. Ogg. thml 1972, e1, 2361 (b) Bubb, w. 1A.; Sternhell, 8. Aust, J. Chem. 1976, 24, 1685. (a) McCullough, J. J. Acc. Chem. Res. 1980, ;;, 270 (b) Thummel, R. P. 12191 1980, lg, 70. (a) Davalian, D.3 Garratt, P. J. J. Am. Chem. Soc. 1975, 91, 6883 (b) Kakiuchi, K.3 Hiramatsu, Y.3 Tobe, Y.3 Odaira, Y. Bull. Chem. Soc. Japan 1980, 5;, 1779 (c) Paquette, L. A.3 Photis, J. M. Org. Syn. 1977, 51, 53 (d) Bartlett, P. D.3 Wingrove, A. S.3 Owyang, R. J. Am. Chem. Soc. 1968, en, 6067. Sasaki, T.3 Kanematsu, K.3 Hayakawa, K.3 Uchide, M. ;;' Chem. Soc. Perkin I 1972, 2750. Thermal Diels-Alder copolymer of similar type of compound 7,16-bis(1-octynyl)-7,16-dihydroheptacene-7,16- diol has been reported. See Sastri, V. R. Ph. D. Thesis, Rutgers University The State U. of New Jersey (New Brunswick) 1984. (Diss. Abstr. Int. B 1985, 4;, 2148.) Bailey, W. J.3 Liao, C.-W. J . C e Soc. 1955, 11, 992. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 153 Cowan, D. 0.3 Drisko, R. L. " Elements of Organic Photochemistry " 1976, pp. 37-74, Plenum Press, New York. Greene, F. D.3 Misrock, S. L.3 Wolfe, J. R. J. Am. Chem. 529; 1955, 11, 3852. Similar phenomenon has been observed, see ref. 51, pp. 65. Friedman, S.3 Metlin, S.3 Svedi, A.3 Wender, I. J. Or . Qnem; 1959, 24, 1287. (a) " Merck Index " 10, 6219 (b) LeHoullier, C. S.3 Gribble, G. w. J. Org. Cnen. 1983, 45, 2364 (c) Gribble, G. W.3 Perni, R. B. J. Qrg. Chem. 1985, 5Q, 2934. Clar, E.3 John, F. cnen. Be;. 1930, 5;, 2967. Marschalk, M. C. Bull. Chim. Soc. Fr. 1938, 5, 157. Clar, E. Chen. Ber. 1942, 155, 1330. Clar, E. " Polycyclic Hydrocarbons " vol. 1, 1964, pp. 60, Academic Press, New York. Buchta, E.3 Egger, H. Chem. Beg. 1957, 55, 2760. For a review, see Hoffmann, R. W. Dehydrobengene and Cycloalkynes, 1967, Academic Press, New York. Rickborn, B.3 Netka, J.3 Crump, S. L. J. Org. Chem; 1986, 5;, 1189. Bailey, W. J.3 Madoff, M. J. J. Am. Chem. Soc. 1953, 15, 5603. (a) Bruckner, V.3 Karczag-Wilhelms, A.3 Kormendy, K.3 Meszaros, M.3 Tomasz, J. Acta Chim. Acad. Sci. Hung. 1960, 1;, 443 (b) Bruckner, V.3 Karczag, A.3 Kormendy, K.3 Meszag, M.3 Tomasz, J. Tetrahedron Lett. 1960, 5. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 154 For reviews see : (a) Haddadin, M. J. negereyeleel 1978, 5, 865 (b) Friedrichsen, W. Adv. Hetercycl. ghem. 1980, 55, 135 (c) Wiersum, U. E. Aldrichimica Acta 1981, 44, 53. (a) Potts, K. T.3 McKeough, D. J. Am. Chem. Soc. 1973, 55, 2750 (b) Potts, K. T.3 McKeough, D. J. Am. Chem; 5ge; 1974, 55, 4268. Cava, M. P.3 Behforouz, M.3 Husbands, G. E. M.3 Srinivasan, M. J. Am. Chem. Soc. 1973, 55, 2561. Fieser, L. F.3 Haddadin, M. J. Can. J. Chem. 1965, 4;, 1599. Sasaki, T.3 Kanematsu, K.3 Iizuka, K.3 Ando, I. J. Org. gnen; 1976, 4;, 1425 and ref. 60. Warrener, R. N. J. Am. Chem, Sog. 1971, 5;, 2346. Wiersum, U. E.3 Mijs, W. J. Chen. Commun. 1972, 347. Marschalk, C. Bull. Soc. Chim. Fr. 1942, (5)5, 400. Mass spectra were recorded by JEOL HX110 HF mass spectrometer using field desorption (FD) technique from the Michigan State Univ. Mass Spectrometry Facility. A TCNE adduct of isobenzofuran has been prepared; see Bremner, J. 8.3 Hwa, Y. Aust. J. Chem. 1971, 54, 1307. Wibaut, J. P.3 Sixma, F. L. J.3 Suyver, J. F. ec . Inev. Chin. Pays-gag. 1949, 55, 525.