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o

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fl“ ..I,,‘ 1.
it“ 1 (”ass

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mirt‘ '
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.' HI
.‘ ‘-‘

This is to certify that the

dissertation entitled

USE OF DI—ARYNE EQUIVALENTS IN THE
SYNTHESIS OF NOVEL ARENES

presented by

Mary Ann Babin Meador

has been accepted towards fulfillment
of the requirements for

Ph.D. degreein Chemistry

 

 

4

Major professor

DMe November 11, 1983

 

MSU is an Affirmative Action I’Equal Opportunity Institution 0— 12771

 

 

 

)V1531_} RETURNING MATERIALS:
Place in book drop to
LIBRARIES remove this checkout from
_—. your record. FINES will

 

 

be charged if book is
returned after the date
stamped below.

 

 

 

 

 

USE OF DI—ARYNE EQUIVALENTS IN THE

SYNTHESIS OF NOVEL ARENES

By

Mary Ann Babin Meador

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of Chemistry

1983

ABSTRACT

USE OF DI-ARYNE EQUIVALENTS IN THE

SYNTHESIS OF NOVEL ARENES

By

Mary Ann Babin Meador

Di-aryne equivalents, generated from tetrahalobenzenes
and n-butyllithium, were used to synthesize a variety of peri-
substituted anthracenes and phenanthrenes. The procedure
involved bis-cycloaddition to substituted furans or pyr-
roles, followed by aromatization of the bis-adducts in
various ways.

The photochemistry of the crowded arenes was studied.

It was found that the series of 9,lO-dialkoxyoctamethylan-
thracenes, as well as 9-methoxyoctamethylanthracene, formed
9,10-Dewar-isomers on irradiation, but these were much less
stable than the 9,10-Dewar-anthracenes produced from irradia-
tion of decamethylanthracene and 9-t-butylanthracene. Ir-
radiation of 1,2,3,A,5,6,7,8-octamethylanthracene at -78°C
produced an unknown radical species as evidenced by its ESR
spectrum. There is no precedent in the literature for such

behavior.

Mary Ann Babin Meador

The synthesis of novel iptycenes from di-aryne equiva-
lents was described. In l,“,5,8-tetrahydroanthracene-l,A55,8-
bis(epoxide)(I), both double bonds are effective dienOphiles.
Thus, I gives a bis-adduct with anthracene which on dehydra-
tion gives 5,9,14,18-tetrahydro-5,18[l',2']:9,lA[l",2"]-di-
benzenoheptacene(II). That is, I is a 2,336,7-anthradiyne
equivalent. The central anthracene moiety in II adds benzyne
to give the novel horseshoe-shaped 5,7,9,lA,l6,18-hexahydro-
5,18[l',2']:7,16[l",2"]:9,lu[l"',2"'J-tribenzenoheptacene.

Similarly, 6,7—dibromo-l,A—dihydronaphthalene-l,A—
epoxide(III) is a 2,3;6,7-naphthadiyne equivalent. Reaction
of III with anthracene produces an adduct which on dehydra-
tion gives 2,3-dibromo-6,ll-dihydro-6,ll[l',2'J-benzeno-
naphthacene(IV). Reaction of IV with n-butyllithium and
furan gives an adduct which can be deoxygenated with low
valent titanium to give 5,1A-dihydro-5,lA—[l',2']-benzeno-

pentacene.

With Love, to Mike

ii

ACKNOWLEDGMENTS

I wish to express my sincere gratitude to Professor
Harold Hart for his encouragement and guidance throughout
the course of this study, as well as his limitless patience
through my bout with morning sickness.

Appreciation is extended to Michigan State University,
the National Science Foundation and the National Institute
of Health for financial support in the form of teaching and
research assistantships.

I would like to thank my family and friends for
their love and support over the past few years. I especi-
ally owe my parents a debt I can never repay.

Last and most, I thank my husband, Mike, for never

allowing me to quit.

iii

Chapter

LIST OF TABLES.

TABLE OF CONTENTS

LIST OF FIGURES

INTRODUCTION.

RESULTS AND

Part I.

E.

Part II.

C.

DISCUSSION.

Synthesis and Reactivity of
Sterically Crowded Anthracenes

Preparation of Arenes
Photochemistry.

Unusual Behavior of l,2,3,4,5,6,7,8-
Octamethylanthracene, QZ' . . . . . .

Reactions of Anthracenes with Tri-
fluoroacetic Acid . . . .

Conclusions

Synthesis of Some Novel Iptycenes
Using Di-aryne Equivalents.

Use of a 2,3;6,7-Anthradiyne Equivalent
in Synthesis of a Novel Pentiptycene.

Synthesis of a Triptycene From a
2,3;6,7-Naphthadiyne Equivalent

Suggestions for Further Studies

EXPERIMENTAL.

General

Procedures.

9,lO-Dimethoxyoctamethylanthracene, éfi- . .

iv

Page

. viii

ix

22

22
2A

37

us

50
56

58

59

65
69
75
75
75

Chapter Page

Tetrabromohydroquinone, IAQ . . . . . . . . . . 76

2 ,3 5, 6- Tetrabromo- l, A- diethoxy-
benzene, 79. . . . . . . . . . . . . . . . 77

9,lO-Diethoxyoctamethylanthracene,

1% 77

2,3,5,6-Tetrabromo-l,A-di-
is0propoxybenzene, 7g . . . . . . . . . . . . . 78

9, 10- Diisopropoxyoctamethyl-
anthracene, 7%. . . . . . . . . . . . . . 78

2,3,5,6-Tetrabromo-A-(bromomethyl)-
anisole, I56. . . . . . . . . . . . . . . . . . 79

2 3, 5, 6- Tetrabromo- A- (acetoxymethyl)-
anisole, IAZ. . . . . . . . . . . . . 79

2 3, 5, 6- Tetrabromo- A- (hydroxymethyl)-
anisole, IAQ. . . . . . . . . . . 8O

2,3,5,6—Tetrabromoanisole, ZA . . . . . . . . . 8O

1,2,3,u,5,6,7,8-Octamethyl-9-
methoxyanthracene, 18 . . . . . . . . . . . . . 81

1,2,3,A,5,6,7,8-Octamethyl-1,A,5,8-
tetrahydroanthracene-1,A,5,8-bis-
(epoxide), 77 . . . . . . . . . . . . . . . . . 82

1,5,9,10-Tetramethyl-1,A,5,8-tetra-
hydroanthracene-1,A;5,8—bis(epoxide),

g9 82

l,8,9,lO-Tetramethyl-l,A,5,8-tetra-
hydroanthracene-1,A;5,8—bis(epoxide),

9,10-Diisopropoxy-l,A,5,8-tetrahydro-
anthracene-1,A,5,8-bis(epoxide), 8% . . . . . . 83

Diethyl Diglycollate, lAg . . . . . . . . . . . 8A

Diethyl 3,A-dihydroxyfuran-2,5—
dicarboxylate, ISO. . . . . . . . . . . . . . . 8A

Chapter Page
Diethyl 3,A-dimethoxyfuran—2,5-
dicarboxylate, 88%. . . . . . . . . . . . . . . 85

3,A-Dimethoxyfuran—2,5-dicarboxylic

acid, $86 . . . . . . . . . . . . . . . . . . . 85

3,A-Dimethoxyfuran, 8%. . . . . . . . . . . . . 86
2,3,6,7,9,lO-Hexamethoxy-1,A, 5,8-
tetrahydroanthracene-l, A;5,8- bis-
(epoxide), 88 . . . . . . . . . . . . . . . . . 87

6,7-Dibromo-5,8-dimethyl-l,A-di-
hydronaphthalene-l,A-epoxide, 88. . . . . . . . 88

l,9,10—Trimethyl-1,A,5,8-tetrahydro-
anthracene-1,A;5,8-bis(epoxide), 88 . . . . . . 88

9,lO-Dimethoxyanthracene, $5. . . . . . . . . . 89

1,2,3,A,5,6,7,8-Octamethylanthracene,
fix. 0 o o o o o o o o o o o o o o o o o o o o o 90

1,8,9,IO-Tetramethylanthracene, 88. . . . . . . 9O
1,5,9,lO-Tetramethylanthracene, 89. . . . . . . 9O
9,lO-DiiSOprOpoxyanthracene, 98 . . . . . . . . 91

2,3,6,7,9,lO-Hexamethoxyanthracene, 9%. . . . . 91
2,3,6,7-Tetrahydroxyanthroquinone, 88%. . . . . 92
l,9,10-Trimethylanthracene, 92. . . . . . . . . 92
A,5-Dibromo-3,6-diiodoveratrole, 98 . . . . . . 93

9,lO-Dimethoxyoctamethyl-l,A,5,8-
tetrahydrophenanthrene-l,A;5,8—
bis(epoxide), 9x. . . . . . . . . . . . . . . . 93

9, 10- -Dimethoxyoctamethy1phen-
anthrene, 98. . . . . . . . . . . . . . . . . 9A

General Procedure for Photolysis of
Anthracenes and Phenanthrenes . . . . . . . . . 95

Irradiation of 1,5, 9,lO-tetramethy1-
anthracene, 89, in the Presence of
Oxygen. . . . . . . . . . . . . . . . . . . 95

vi

Chapter

Irradiation of 1,8,9,lO-tetramethyl—
anthracene, 88, in the Presence of

Oxygen. . . . .

Reaction of Octamethylanthracene .81

with TFA.

Reaction of 9-methoxyoctamethy1-

anthracene 78 with TFA.

Reaction of 9,lO-dimethoxyoctamethyl-

anthracene 89 with TFA.

1, A 5, 8- -Tetrahydroanthracene- -1, A :,5 8—

bis(epoxide), 1&8.

Adduct of Anthracene and bis- epoxide

18% (181)

Pentiptycene, 128

Attempted Reaction of Pentiptycene
iiQ With 1,2,“,S—tetrabromobenzenes,

, 19 and Ag

Attempted Reaction of Pentiptycene 128

with Diaryne Precursor 838.

Attempted Reaction of Pentiptycene .188
with Bis- epoxide 1&8 (anti)

6 ,7 Dibromo- 1, A- dihydronaphthalene- l ,A-

epoxide, 13g.

Adduct of 13% and Anthracene (I88).
3,A—Dibromo-[2b.l.1]triptycene, I88
Adduct of 135 and Furan (188)

[3b.l.l]-Triptycene, 131-

Bibliography.

vii

Page

96

96

97

97

98

99

100

101

101

102

102
103
103
10A
105
106

Table

LIST OF TABLES

Synthesis of 9,lO-dialkoxyoctamethylan—
thracenes Using Di-aryne Equivalents.
Bis-annelation Using Furans as

Dienes. . . . . . . . . . . . . . . .
Deoxygenation of Bis—adducts Using

Low Valent Titanium . . .

Spectroscopic Data for 9,10-Dewar—

anthracenes . . . . . . . . . . . .

viii

Page

25

28

31

A1

Figure

LIST OF FIGURES

Page

Other Dewar-anthracenes . . . . . . . . . . l9
Ultraviolet spectrum of 9,10-diethoxy-
octamethylanthracene 1% (solid line)

and its 9,10-Dewar-isomer 19% (broken

line) at -A5°C in hexane. . . . . . . . . . A3
1H NMR spectra of products of the

photolysis of l,A,9-trimethylanthracene,

188, in three different solvents: a)
pyridine-d5; b) benzene-d6; c) chloro-

form-d showing the region from 62 to 65 and

d) the 13C NMR in chloroform-d. . . . . . . AA
Methyl region from spectrum 3a, expanded

to show five methyl peaks . . . . . . . . . A6
ESR spectrum of radical from the

photolysis of octamethylanthracene, 81,

in toluene at -lOO°C. . . . . . . . . . . . A8
a) ESR spectrum observed on addition

of 1 eq trifluoroacetic acid (lM in CDCl3)

to octamethylanthracene, 81, in CDCl

3
(mlO-BM); b) ESR spectrum produced in

ix

Figure Page

6 Cont. similar manner from 9-methoxyocta—
methylanthracene, Z§. . . . . . . . . . . . 52
7 Endo-approach in Diels-Alder reaction
between bis-epoxide lag and penti-

ptycene lgfi . . . . . . . . . . . . . . . . 65
8 End on View of heptiptycene lgg . . . . . . 7O

INTRODUCTION

Benzynes have been used extensively in organic syn-
thesis for many years.1 In comparison, investigation of
the enormous potential of di-aryne equivalents for the
construction of complex ring systems has only begun.

Use of the terms di-aryne and di-benzyne does not
necessarily imply that the reactions which will be discussed
proceed through intermediates such as l and g. Dibenzynes,

however, have been proposed as intermediates in certain mass

spectral fragmentations, and have been used to rationalize
products from the co-pyrolysis of pyromellitic (§) or mella-
phanic (A) dianhydrides with benzene2 (see Scheme 1).

These reactions may proceed as postulated, or they might

proceed in a stepwise manner. Indeed, when a less active
arene, such as chlorobenzene, is used as the trapping agent

3

products which still contain one anhydride ring are ob-

served.

Wittig3 introduced di-aryne equivalents in 1959 with

the conversion of 5 to 1. The yield of 1 was low, however,

Mg n-BuLi
é §LM
F F £l__;€, [liili £34915 ()015
Br Br THF Br

101
lm

«a w

[\l

and 5 was a difficult starting material to prepare.
Giles3 used a di-aryne equivalent to synthesize the
bis-epoxide, l2. But the reaction was carried out in two

steps since a higher reaction temperature was required for

addition of the second furan moiety than for the first.
The overall yield of bis—adduct kg for the two-step process

was 36%.

ONE \ 0M5
Br NaNHZPQ 3"
0 __.__. (so...
Br THF, A
0M3 0M3

9. ~ °®
HQNHZ , /

MeOCH2CH20Me.
v A.

£0

 

OMe

” a (57 ‘70)

0Me
IO

M

Wege and Stringer,5 in work reported after studies on
di-arynes were initiated in this laboratory, synthesized
some novel furan derivatives of triphenylene (i434, lé and
$9) via o—di-aryne equivalents (see Scheme 2). The re—
ported yields of the bis-adducts lg and l5 were low. How-
ever, much unreacted starting material, as well as mono-

adduct, was recovered in each case, since the authors

stated that allowing the reactions to go to completion
resulted in degradation of the products. Thus, the degree
of conversion was actually much higher than the reported
yield.

An improved method of generating di—aryne equivalents
has been developed by Hart and co-workers in recent years.6

The method makes use of the relatively easy-to-prepare

tetrabromoarenes,such as ll. Reported yields for these

 

 

13 L8, (70%)

reactions are generally good (60-80%), and the scope of the
method is limited only by compatibility of the diene (and
substituents on the dienophile) with n-butyllithium.
Di-aryne equivalents have been shown to be particularly
useful in the synthesis of fused aromatic systems.6'lo
A wide range of substituted anthracenes have been syn-

6’8 in two steps from

thesized by Hart and co-workers
suitably substituted benzenes. The procedure involves bis-
annelation of substituted furans or pyrroles, followed by

‘ aromatization in various ways. For example, the bis-epoXides,

g9 or lg, can be prepared in good yield from ll or l2, and

furan. Deoxygenation is carried out in a single step using

R
8" D B? n-BULi MR
8 Br
R
12 W43 20 R=Me (72%)
- L? R=OMe l0 R=OMe (72°70)
W06 or FeCls
. n-BuLi
R
R

21 R= Me (56°70)
g R: OMe (89°70)

low valent metals such as tungsten or iron,8 as opposed to
indirect procedures which involve two steps, hydrogenation
followed by dehydration.

Since the bis-annelation proceeds stepwise,6 the re-

action can be used to make unsymmetric anthracenes. For

example,tfluamono-adduct, gé, can be prepared from £1 and
2,5-dimethylfuran using one equivalent of n-butyllithium.
Adding one equivalent each of N-methyltetramethylpyrrole
and n-butyllithium to the reaction mixture gave the unsym-
metric bis-adduct, 3%. Here, the choice of solvent was
important. With ether or tetrahydrofuran as solvent no

mono—adduct g3 could be isolated. This is probably because

3.

 

 

 

 

3 Bo
. 9
Bf ,. leq n-BuLI
TOLUENE
g
_,($ROMATIZE
25

 

the greater solubility of %% allows it to be metalated
faster than tetrabromo—p-xylene, l1. If toluene is used
as solvent, the solubility of ii is increased, giving a
good yield of g%.

Extension of this methodology to phenanthrenes has

9

been achieved by Hart and Shamouilian by using A,5-dibromo-

3,6-diiodo-o-xylene, gé, as the o-di-benzyne precursor.

Br

 

$3.,

This reagent was selected in order to direct lithiation to
give the desired product (iodine exchanges faster than
bromine).

LeHoullier and GribblelO recently used a similar method
for generating a naphthadiyne equivalent in the two—step
synthesis of chrysenes, 3% and éA (see Scheme 3). The
2 , 6-dibromo-l , 5-bis-[(p-tolyl sulfonyl )oxy] naphthalene , g9 ,

was easily prepared in 9A% yield from commercially available

@53-

10

 

 

OH
00 5" p~1oluenawlfonyl~CL
Br ~ acetone. MOH»°° I
OH

2.2

 

 

Scheme 3.

ll

Di-arynes can be trapped by anthracene to give some
novel "iptycenes."* The pentiptycene, 3Q, was first pre-
pared from triptycyne equivalent, 35, (not itself trivial

12

to make!) in a 10% yield. The overall yield of 3% from

available starting materials was only 1.2% (5 steps).

 

The di-t-butyl derivative, 3%, was synthesized from

di-aryne precursor 31 in a 2% yield, along with some l,A-

di-t-butyl-triptycene, gg.l3

 

*The name "iptycene" emphasizes the relationship between
these compounds and the parent structure, triptycene.

A prefix indicates the number of separated arene planes;
thus, above is a triptycene (three planes) and 3g is

a pent ptycene (five planes).ll

12

 

Br 333' Q] +

Hart, Shamouilian and Takehirall

have synthesized 36

in a much improved yield, and in only one step from avail-
able starting materials. They also prepared the new 0-
pentiptycene, Al, and l.l.2(b)b.l.l pentiptycene, A3 (see
Scheme A).

Di-arynes have been shown to be useful synthons for

fused aromatic compounds containing large peri-substituents.

Since the steric strain is introduced over two steps -- the
first an exothermic benzyne reaction, and the second driven

by aromatization -- the molecule is cajoled into accepting

6,7

1A

it. For example, decamethylanthracene, A , was synthe—
’b

6

sized in 72% overall yield from TX and N,N-dimethylamino-

tetramethylpyrrole, a substantial improvement over the

 

 

Br
B!“ r
.EZ
|80°C
VACUUM
eg (72%)
earlier eight-step synthesis.lu Similarly, dodecamethyl-

naphthacene, Al, was prepared from the naphthadiyne equiva-

lent 36 in a 62% overall yield.6

15

 

 

Br 8.
Br~ 3,,
33 g§(52°k»
180°C
VACUUM

 

 

93 (99%)

Compounds such as A5 undergo some unusual reactions as
a consequence of the steric strain in the system. For ex-
ample, decamethylanthracene, $5, in the presence of a trace

1A Ir-

amount of acid, will isomerize to the tautomer Ag.
radiation of A5 in benzene (or ether) produces the 9,10-
Dewar-isomer Ag, which thermally reverts to the anthracene.
Both of these rearrangements serve to buckle the middle ring,

relieving the four methyl-methyl peri-interactions.

l6

 

 

 

Other aromatic compounds containing sterically bulky
substituents also undergo photochemical valence isomeriza-
tion to their Dewar-isomers. The first example of such
compounds was van Tamelen's l,2,A-tri-t-butylbenzene,

59.15 Again, the Dewar-isomer, 5i, thermally rearranges to

the starting material.

l7

 

 

Peri-di-t-butylnaphthalenes such as 5% also have been

16a

photolyzed to afford hemi- Dewar-naphthalenes. Curi-

ously, 5% gave the hemi-Dewar, 53a, as the sole isomer.

 

hv \ I

 

 

g2, ééc

None of the hemi-Dewar—isomer 53b could be detected.

_J_

 

18

Some tri-t-butylnaphthalenes also yield hemi-naphtha-
valenes under irradiation. For example, naphthalene 53

phOtOlyzes to hemi-naphthavalene 55 in 95% yield.16b

0 hr O;

54 55

~

\/

Surprisingly, the 1,2,3,A-tetra-t-butylbenzene 56 is
converted thermally to its Dewar-isomer, 51 which reverts

to 56 photochemically.l7 This reversal in reactivity

 

clearly indicates that the Dewar-benzene 5g is actually

lower in energy than its very crowded, aromatic valence

isomer, 56.

COzCHg A 02CH3
C02CH3 hV 02CH3
57

19

9-t-Butylanthracene 5Q is the only other anthracene

reported to photoisomerize to a 9,10-Dewar-anthracene, 59.18

Other Dewar-anthracenes have been synthesized through

03.» 0;
\A ,

is as,

Hz

 

19-22

chemical means, however. These are shown in Figure l.

'

00‘” ' a“;
6320 l Cl g .D

Figure 1. Other Dewar-anthracenes.

20

Less crowded anthracenes, such as 6A, are known to

photodimerize,23 but only if unsymmetrically substituted
in the 9,10-positions.

The reactions generally give the
head-to-tail isomer, 65.

The only exception is with

 

 

R
o m, \
RI
6,30 R=R’=H
b R=Me, R: H
c R=M¢O,R’..H
d R=Me, R’= M30

anthracenes linked as in 66.26

Here, the only possible
product is the head-to-head isomer 61

 

Qulfi
4‘ o

67
95.

~

 

21

This thesis will deal, in part, with the synthesis of
some other peri-strained anthracenes through di-aryne
equivalents. In order to examine the conflict between
steric bulk and aromatic character that is inherent in
these hindered compounds, their photochemical valence
isomerizations and other interesting reactions will be
discussed.

In addition, extension of bis-annelations to the syn-
thesis of some other novel compounds, such as "iptycenes,"

will be described.

RESULTS AND DISCUSSION

Part I. Synthesis and Reactivity of Sterically Crowded

Anthracenes

 

In both decamethylanthracene, £5, and 9-t-butylanthra-
cene, 5%, the 9,lO-Dewar-isomers are photochemically ac-
cessible most likely because steric bulk destabilizes the
fully aromatic structure relative to its valence isomer.
The question arises, then, of how much steric bulk is

necessary to drive the reaction.

 

It is clear that the anthracene system is more sensi-
tive to steric strain than either naphthalenes or benzenes.
A single 9-t-butyl group is enough to give rise to the
9,lO-Dewar-anthracene in the case of 5Q. The naphthalene

sYStemrequires at least 1,8-di—t—butyl substitution, and,

22

23

permethylanthracene, A5, is photoisomerized very readily,
whereas permethylnaphthalene, 6%, does not photoisomerize

at all.27

These observations are not surprising since it is well-
established that anthracenes are highly reactive in the
9,lO-positions. This is because the two, smaller, iso—
lated aromatic rings in the product may have as much (or
even more) aromatic stabilization as the reactant. Hence,
less resonance energy is lost in going from an anthracene
to its 9,lO-Dewar isomer than in the same reaction with
naphthalene or benzene (benzene losing the most).

Due to this relative ease of photoisomerization, it
was of interest to further explore the photochemistry of
other peri-substituted anthracenes. In this part, the syn-
thesis of a variety of such compounds will be described and

their photochemistry examined.

2A

A. Preparation of Arenes

 

The first compounds selected for study were a series of
9,lO-dialkoxyoctamethylanthracenes, 69, ll, and 13. These
compounds should be nearly as crowded as decamethylanthracene,
66, but not as sensitive to acid. In addition, varying the
R-group to change the degree of steric hindrance would be,

synthetically, very simple. These compounds were synthesized

 

as shown in Table 1, from the corresponding di—aryne equiva-
lent and N,N-dimethylaminotetramethylpyrrole. In a typical
procedure, 5 mmol of the di-aryne equivalent and 10 mmol

of the pyrrole in 50 mL dry tetrahydrofuran were cooled to
-78°C and stirred (under argon) as 12 mmol n-butyllithium

in 30 mL hexane was added drOpwise over two hours. The

mixture was allowed to come slowly to room temperature,

25

Table 1. Synthesis of 9,lO-dialkoxyoctamethylanthracenes
Using Di—aryne Equivalents.

 

 

 

eq)
23¢}? :+"<TH |)n-BuLi A Z) I80°

 

 

 

(qu) (Zea)

Di-aryne precursor Product (Yield)
$3 R = Me 66 R = Me (60%)
16 R = Et 1% R = Rt (50%)
1% R = i-Pr 1% R = i-Pr (60%)

 

 

26

then quenched with methanol. Workup involved extraction of
the adduct with methylene chloride. Without further puri-
fication, the residual yellow-brown oil was heated to
180°C under vacuum (20-30 minutes) to remove the nitrogen
bridges. The resulting black residue was purified by
column chromatography and/or recrystallization, giving an
overall yield for the two steps of 50-60%.
9-Methoxyoctamethylanthracene, 16, has two fewer peri-
methyl-methoxy interactions than 66. The compound was
synthesized in the same manner as described for 62, 16,

and 13, from the di-aryne equivalent, 66.

/2\
3

/
ome \ - -
Br Br nail-l ,

 

(w

B' -r 2) IBOOC

B 15, (20°70)

The photochemistry of many, much simpler anthracenes
even those containing only one peri interaction is unknown
in the literature. Consequently, it was decided to examine
several such anthracenes. These were Synthesized utilizing
the two step bis-annelation scheme previously described.

In the first step, di-aryne equivalents were reacted with

27

appr0priately substituted furans to give the desired bis-
adducts (see Table 2). Furans were used in place of pyr—
roles either because the furans containing the desired
substitution were readily available, or the yield using

the corresponding pyrrole was low. In general, the bis-
annelation procedure was the same as that already described.

l,9,lO-Trimethyl-l,A,5,8-tetrahydroanthracene-l,A;5,8-

bis(epoxide), 66, an unsymmetric bis-adduct, was synthesized

in two steps from di-aryne equivalent 61 as shown.

8’ leq n-BuLi \ Br ‘.D
Br r 7 8!“

U7

~

 

29?.

 

 

28’

Table 2. Bis-annelation Using Furans as Dienes.

 

 

 

Di-aryne Furan Product (yield)
‘3' - 6’0“]
Bra: 3
4.9 1,6 r; (7.02.)
3" " ‘ $01!
Br 0 Br 3
)3 73 23 (29%)

 

29

Table 2. Continued.

 

 

Di-aryne Furan Product (yield)

 

 

 

 

3O

Deoxygenation of the bis—adducts was carried out using
low valent titanium by an improved method over that pub-
lished by Hart and Nwokogu8 (see Table 3). These authors
used low valent forms of iron, tungsten, and titanium,
generated by treatment of the metal chlorides with n-
butyllithium. The yields were moderate to good, but the
workup was generally quite tedius.

The improved deoxygenation method involved adding an
excess of powdered zinc to a solution of titanium tetra-
chloride in tetrahydrofuran.29 The resulting blue-gray
suspension was brought to reflux, and the bis-epoxide in
tetrahydrofuran was added. Reflux was generally con-
tinued for five hours, after which time the mixture was
cooled and poured into dilute hydrochloric acid. Workup
usually involved extraction of the yellow solid with methyl-
ene chloride. Evaporation of the solvent gave the de-
sired anthracene in good yield (80-90%) and a high degree
of purity.

30 reported an additional method

Wege and co-workers
for deoxygenating l,A-epoxy-l,A-dihydroarenes with en-
neacarbonyldiiron. The method involved formation of a
tetracarbonyliron complex, such as 96, followed by decom-
position of the complex to yield the arene. This method
also gave clean product in consistently high yields. Un-
fortunately, no comparison of this method with the low

valent titanium method can be made since the authors

31

Table 3. Deoxygenation of Bis-adducts Using Low Valent
Titanium.

 

 

Bis-adduct Product (yield)

 

 

73 83(57 c’2.)

 

32

Table 3. Continued.

 

 

Bis-adduct Product (yield)

 

COO

so 8,3(85 “6)

 

 

 

33

Table 3. Continued.

 

 

Bis-adduct Product (yield)

 

000

83 93(80 ‘2.)

 

 

 

3A

 

0 ~2~ ~> 0

99 9.9.
s

reported no results with bis-epoxides. However, in view
of the high toxicity of iron carbonyl complexes, it is
tempting to say that the zinc-titanium tetrachloride pro-
cedure is the method of choice for deoxygenating such com-
pounds.

Highly substituted phenanthrenes also possess a high
degree of steric strain, especially if substituted in
the A- and 5-positions.31 Thus it was thought that 9,lO-
dimethoxyoctamethylphenanthrene, 66, and decamethyl-
phenanthrene, 66, might undergo some photochemical valence

isomerization.

35

0 ~ 0
“‘0 ’0

98 93

~

The 9,lO-dimethoxy derivative, 26, was synthesized
in two steps from di-aryne equivalent 26 and tetramethyl
furan, 16, as shown in Scheme 5. Bis-adduct 21 could
not be isolated, but the crude product was used directly
for deoxygenation with low valent titanium. The overall
yield for both steps was 20%. Decamethylphenanthrene, 26,
was synthesized by Hart and Shamouilian,in a similar

manner from di-aryne precursor 66 in A0% overall yield.9

 

36

n-BuLj !>_

 

Scheme 5

 

37

B. Photochemistry

 

The photolysis of the arenes previously described was
followed by NMR spectros00py. In a typical procedure, a
solution of lO-l2 mg of the arene in 0.5 mL of benzene-d6
(or toluene—d8) was placed in a 5 mm NMR tube and flushed
with nitrogen. Irradiation of the sample for 60-90 min-
utes using a Hanovia A50 W medium pressure lamp with Pyrex
filter was carried out by taping the sample tube directly
to the cooling Jacket of the lamp. If low temperatures were
required, the lamp and cooling Jacket along with the sample
were emersed in a dry ice-is0propanol bath, and dry nitrogen
was passed through the cooling Jacket.

The series of 9,lO-dialkoxyoctamethylanthracenes,'66,-
Z}, and 16, were found to undergo photochemical valence

isomerization to the 9,lO-Dewar isomers, but these were

 

 

 

69 R= Me '29 R=Me
N

7: R= 5+ '2', R“?
73 R = i-Pr‘ L03 R: 34’?

38

only stable at temperatures lower than -30°C. The most
likely explanation for this decreased stability compared to
decamethyl-9,lO-Dewar-anthracene, 62, is that while forma-
tion of the Dewar isomers is a photochemically allowed
concerted process, the thermal reversion must proceed through

a diradical intermediate, i.e., 666. A structure such as

 

666 would be more stabilized by alkoxy groups than by

methyl groups, as in decamethylanthracene, 66.
Interestingly, the stability of these 9,lO-Dewar-

anthracenes relative to their aromatic valence isomers

does not increase with increasing size of the alkoxy groups.

39

9,lO-Dimethoxy-9,lO—Dewar-anthracene 166 reverts to 66

at -30°C with a half-life of approximately one hour. The
diethoxy derivative, 161, rearranges to anthracene 11 at
-50°C with a half-life of thirty minutes, and 9,lO-di-
isopropoxyoctamethylanthracene 166 rapidly reverts to 16
above —60°C. This must be because steric hindrance is also
a factor in the stability of the Dewar isomers. Torsional
strain in the Dewar isomers increases along the series di-
methoxy<diethoxy<di—iSOpropoxy. The number of unhindered
conformations would decrease along the same series resulting
in an entropic destabilization.

Low temperature photolysis of 9-methoxyoctamethyl-
anthracene, 16, yields the 9,lO-Dewar-anthracene 666, which
reverts to starting anthracene at -30°C with approximately
the same half-life as 9,lO-Dewar-isomer 166. Thus, one
less peri-substituent (i.e., less steric strain in the
anthracene) must balance the effect of one less oxygen
to stabilize the diradical intermediate in the thermal

reversion.

 

 

 

A0

The 9,lO-Dewar-anthracenes discussed could not be
isolated, but were identified by their proton and 130 NMR
spectra, as well as their ultraviolet spectra (see Table
A). A typical ultraviolet Spectrum of a 9,lO-Dewar-isomer
is shown in Figure 2. The spectros00pic data are in good
agreement with that for 9-t-butyl-9,lO-Dewar-anthracene
6618 and decamethyl-9,lO-Dewar—anthracene 66.1“

l,A,9-Trimethylanthracene, 166,32 was irradiated in

benzene at room temperature, giving a phot0product that

was stable even above 60°C.

I 5

N

The l

H NMR spectrum (aliphatic region is shown in Figure 3)
shows that the aromatic singlet for C-lO in anthracene 166

has been replaced by a singlet at 6A.27 (in CD013). In
addition, the methyl peaks have all shifted upfield by
approximately 0.5 ppm. The 13C NMR spectrum (also shown

in Figure 3) has new peaks at 662.27 and 65A.07, and shows

an upfield shift by the methyl carbons. The spectra are
consistent with that of the 9,lO—Dewar isomer of 166 (the

C-10 proton should appear at 6A-5, and the 130 chemical shifts
for C-9 and C-10 should be between 650 and 565). However,

it is conceivable in this case, since 666 is unsymmetrically

ill

 

 

 

Amm .Nmo .pdmmv No.3
Amma .mv Hm.m
o o Amma .mv mm.H
Ammfi .Nmo .cv sm.H
Am: .Nms .uv No.3
Amma .mv om.m
as com o Amma .mv mm.a
Ame .Nms.pv sm.H
2
00.
“4‘.
moi: .363 :6 .3 Sam OA'O
e: osm .mo.mma .sm.aoa Amma .mv mm.m
3.? £93 .30.? Ema .3 $4 u .
AmeKV n>o Ago mmzz omH on mmzz ma spasm

 

 

.mocoomsspcmupwzooloa.m pom mama Ofiaoomoppooom

.: magma

H2

.Edpuooqm :Hmpoo op oaompmcs oou osmowpnpcmummsomloa.mo

.mhzumnooEop meow on» no cocamuno
mums mpuooam .oomzl pm ocmxoc :fi Haoo >D|Lm3oa aunmsv CH commaouonq who: moHQEmmn

.ooowl on 00:: um oohsmmme who: mpuooom

.Oowwl pm moon mzz cm ca monocosaop Ca mocoompnpcm on» wcfiumaopono nouns oocfimpnom

 

 

 

2

«a:
Ama .mv 2a.:
mo.::a .mm.m:H Amm .mv o=.m
.mm.mma .mm.:ma Ame .mv mm.m
.zm.mma .os.mma mm.mm . Ame .mv ma.m
.mo.:m .sm.zm .mm.ma Ame .mv mm.a

E: msm .Ho.mH .mm.mH .zm.mH Ame .mv om.a o
.
Axmsxv p>p Amy wmzz umH Acv mmzz ma spasm

 

 

.cmscfipcoo .z magma

“3

 

 

 

Figure 2. Ultraviolet spectrum of 9,lO-diethoxyocta—
methylanthracene (solid line) and its 9,

lO-Dewar-isomer l (broken line) at -u5°C
in hexane.

uu

 

 

 

 

’ V
'3 V
k;
a.
V
\’v
V in
i M b.
V V V

 

 

 

 

 

 

 

Figure 3. 1H NMR spectra of products of the photolysis of
l,u,9-trimethylanthracene, lgg, in three dif—
ferent solvents: a) pyridine-d ; b) benzene-d6;
c) chloroform—d showing the region from<M2to 55;
and d) the 13C NMR in chloroform-d. (Arrows in-
dicate peaks belonging to major phot0product.)

“5

substituted in the 9,lO-positions, that a photodimer could
also be produced.23 The spectral data are consistent with
that structure also.

Close inspection of the spectra reveals a minor product
which appears to be isomeric with the major product. In the
proton spectrum in CD013, a second bridgehead proton peak is
found at 6u.h5, and there is an extra peak in the methyl
region. Integration of the spectrum shows a 5:1 ratio be-
tween the two bridgehead peaks. There is also a 5:1 ratio
between the methyl peaks at 62.39 and 62.50, and coinciden-
tal overlap of the other two methyls in both isomers at
62.25 and 2.55 is consistent with the integration. The
proton spectrum in pyridine—d5 shows five separate methyl
resonances (see Figure 3 as well as expanded methyl region
shown in Figure 4). The 130 NMR spectrum also shows a sec-
ond C-lO bridgehead peak at 650.20, (since C-9 is quaternary,
it is reasonable that the concentration of minor isomer is
too low to see this peak) and a total of five methyl peaks.

Since there is only one possible structure for the 9,lO-
Dewar-anthracene ($06), and there are four possible struc-

tures for the photodimer ($01 - llg), the two isomeric
1

 

:29

U6

A A A

Figure A. Methyl region from spectrum 3a, expanded to show
five methyl peaks.

 

products must be the latter. Since photodimerization gen-

erally yields head-to-tail products, the isomers produced

Q'D Q‘D

Q‘D

ICE; ' IIC)

 

”7

are probably IQ; and lgfi. Photodimer £01 is most likely
the major phot0product, since it would be the least
sterically hindered.

Unfortunately, none of the other anthracenes or phen-
anthrenes synthesized for this study underwent photochemical
valence isomerization to Dewar isomers even at -78°C.
However, both tetramethylanthracene derivatives, fig and 63,
reacted readily with singlet oxygen to give the endo-per-

oxides, Ill and Ila, respectively. It is well established

by
02

 

 

zg
2

hr

 

 

ua

that anthracenes give endOperoxides with singlet oxygen,23
but with fig and fig: the reaction was so facile that isola-
tion of these hydrocarbons had to be carried out in the
dark (i.e., fluorescent laboratory lights were sufficient

to bring about their photo-oxidation).

C. Unusual Behavior of 1,2,3LH,5,6,7,8-Octamethylanthra-

cene, 61

Octamethylanthracene, $1, when irradiated at -78°C

 

in either degassed or undegassed samples, produces an un-
known radical species as evidenced by its ESR signal (Fig—

ure 5) and the complete disappearance of its 1H NMR spectrum.

3414
l

 

Figure 5. ESR spectrum of radical from the photolysis of
octamethylanthracene, QZ’ in toluene at -100°C.

“9

The radical species decayed above —30°C to give back octa-
methylanthracene, QZ, unchanged.

Since its ESR spectrum does not show any hyperfine
coupling, it is difficult to make any suggestions as
to the nature of the radical species. One possibility,
though, would be a diradical species, such as llé. Di-

radicals similar to ll; have been proposed as intermediates

 

 

$00 “" "78° A

Q?

 

23

in the photodimerization of anthracenes. In the present
case, if ll; is formed, it may be too sterically hindered
to close to the dimer and simply dissociates.

There is no precedent in the literature for such a di-
radical species, nor did any of the other compounds studied

here exhibit similar behavior. Even l,h,5,8-tetramethyl-

anthracene, llg,33 which should be about as sterically

50

hindered as 61, did not react under the same conditions

of irradiation. Apparently, the radical species, whatever

hv

 

> NO REACTION

LL‘l

it is, is stabilized by the four additional methyl groups

of @Z.

D. Reactions of Anthracenes with Trifluoroacetic Acid

Peri-strained anthracenes substituted with methyl
groups in the 9- and/or lO-positions rearrange in acid
to give stable hydrocarbon analogues of 9-anthrones.1u’3l4
For example, 1,8,9,lO-tetramethylanthracene, 6%, in the

presence of acid, rearranges to ll5.3u The reactions of

H'-

00
m
0‘ I

l

51

strong acid with peri-strained anthracenes containing
hydrogens or alkoxy groups in the 9,lO-positions is un-
known.

Octamethylanthracene, 61, with trifluoroacetic acid
in chloroform, is very easily oxidized to its radical
cation as evidenced by the ESR signal (see Figure 6a).

Although some 507 peaks are predicted, no fine structure

TFA
(UiCk3

87 H

N

can be observed in its ESR spectrum even at -60°C. This
radical cation, unlike the species produced photolytically,
is very stable at room temperature, and on quenching with
water gives back octamethylanthracene, 61.

Again, 1,4,5,8-tetramethylanthracene, llg, under the
same reaction conditions, exhibits no ESR signal. This
behavior is simply due to a difference in oxidation po-
tentials.35 The radical cation of anthracene itself can
be produced by oxidation with thallium (III) trifluoro-
acetate in trifluoroacetic acid.37 But there are only

a few examples of anthracenes with a low enough oxidation

<E-IC%€>

b)

Figure 6.

52

3494

 

a) ESR spectrum observed on addition of 1 eq
trifluoroacetic acid (lM in CD013) to octa-

methylanthracene, 61, in CDCl (mio-ZM); b)
ESR spectrum produced in simi ar manner from
9-methoxyoctamethylanthracene, Z5.

53

TFA

 

s N0 REACTION
was

potential to give rise to the radical cation in the presence
of trifluoroacetic acid.38

0n addition of trifluoroacetic acid to a solution of
9-methoxyoctamethylanthracene 15 in chloroform, a weak
ESR signal was obtained which appeared at the same position
as that for octamethylanthracene, fix, giving evidence for
formation of a radical cation (see Figure 6b). This signal
decayed after several hours. On quenching with water and
removing the solvent, a white solid was isolated, mp
2A5—2M8°C. The 1H NMR spectrum of this solid consisted
of five singlets (62.28, 2.31, 2.35, 2.5M, 3.56) with an
integration ratio of 3:3:3z3zl. The infrared spectrum

1 and 1655 cm"1

showed strong bands at 1670 cm” , and the
mass spectrum had a strong molecular ion peak at m/e 306
and a base peak at m/e 291. All of the spectral data of
the product are consistent with the octamethylanthrone llfi
(lit.39 mp 251-25200).

With 9,lO-dimethoxyoctamethylanthracene 6% in chloro—

form, addition of trifluoroacetic acid caused the solution

54

 

 

to turn dark blue, suggesting the formation of a radical

cation. But the color faded in an instant to pink, and no

 

0::
.35»
cu
I
+259

55

ESR signal could be observed. Quenching with water and
removal of the solvent gave a pink residue. Fractional re-
crystallization of the residue with acetone gave two pro-
ducts, both white crystalline solids, in a 3:2 ratio.

The 1

H NMR of the minor product (119p), mp 290-292°C,
consisted of five singlets (61.35, 1.94, 2.20, 2.49, 4.51)
with an area ratio of 6:6:6:6:1. The infrared spectrum

1 and 3690 cm-1

had strong bands at 1680 cm' , and the
highest mass peak in the mass spectrum (also the base
peak!) was m/e 305 (M+-0H). These data suggest a struc-

ture like that shown for 1196.

 

The major product (119a), mp 278-280°C, showed no
carbonyl bands or hydroxy groups in the infrared spectrum.
The 1H NMR spectrum consisted of only two singlets (62.51,
2.28) in an integral ratio of 1:1. The 13C NMR spectrum
showed three aliphatic peaks (616.90, 17.19, H9.15) and
four aromatic peaks. The mass spectrum had a strong peak at

m/e 320 and a base peak of m/e 305. In spite of the

56

simplicity of the spectral data, no good suggestions can
be made at this time as to the structure of this product.
Thus, it appears that both alkoxy and hydrogen sub-
stitution in the 9,lO-positions give rise to radical
cations in the presence of acid. The presence of alkoxy
groups in these positions, however, leads to further re-

action.

E. Conclusions

Although the success rate for designing anthracenes
with photochemically accessible Dewar-isomers has not
been very high, some conclusions can be drawn which may
serve as a guide to future research. First, a large degree
of steric strain is a factor, but there seems to be a
balance between steric strain in the anthracene and that
in the Dewar-isomer. For this reason, a compound such

as 129 might be interesting. Although 120 should be

IZO

57

somewhat sterically hindered, the corresponding 9,10—Dewar-
isomer should be relatively strain-free, and therefore,
stable.

Second, 9,10-dialkoxy groups destabilize 9,10-Dewar-
isomers relative to their corresponding anthracene valence
isomers. However, alkoxy or other hetero—atom groups may

not be a problem in other positions, as in compounds 12%

and 122.

   

l2| l2?

In any case, it must be pointed out that many an-
thracenes belong in a large gray area where they are too
hindered to photodimerize, but not hindered enough to

form a stable 9,10-Dewar-isomer.

58

Part II. Synthesis of Some Novel Iptycenes Usinngi-
aryne Equivalents

, Norbornene derivatives, such as l,A-dihydronaphthalene-

l,A-epoxide, 93, are effective dienophilesflo’ul For ex-

ample, Wittig showed that 93 reacts in high yield with
anthracene andcnnkn'polynuclear aromatic compounds to

give novel cycloadducts such as 123.40 The oxygen bridge

033
‘w men?

A

 

 

93

N

 

N

in 123 can be easily removed with hydrochloric acid in'
acetic anhydride to produce 5,12-benzeno-5,l2-dihydro_

naphthacene, 1,25,. Thus, many interesting compounds can

 

 

59

be made in two steps from the readily available epoxide

23:-

A. Use of a 2,3,6,7-Anthradiyne Equivalent in Synthesis

of a Novel Pentiptycene

 

1,4,5,8-Tetrahydroanthracene-l,ug5,8—bis(epoxide) 125
can be synthesized from 1,2,4,5-tetrabromobenzene £8 and
furan in 71% yield by a procedure similar to that described

in Part I. The bis-epoxide 125 was isolated as a 50:50

 

 

mixture of syn- and anti-isomers. These could be separated

 

by trituration with methanol (the syn-isomer is soluble and

the anti-isomer is not).

 

Bis-epoxide 125 should also react with a wide variety
of dienes. And since the oxygen bridges in the resulting
cycloadducts should be easily removed to give an aromatic
product, 125 can be regarded as a synthetic equivalent of

2,3;6,7-anthradiyne 136.

60

IO 0]

L23

Reaction of bis-epoxide 115 with two equivalents of
anthracene in refluxing xylene gave the bis-adduct 111.

Anti-115 gave one isomer of 111 (mp HHO°C, dec.), and syn-

 

115 gave another isomer of 111 (mp 395°C, dec.). The
two isomers were identified by their NMR spectra. The

”0"” + 73%

l25
~J .
(syn or onh)

   

H H H H H0
“ow
HHH I-IIIHHO

l27

~

proton NMR spectrum of the isomer from syn-115 showed
three four-proton singlets for the three sets of bridge-
head hydrogens (62.13, N.35, “.80), and a singlet for the

two uncoupled aromatic hydrogens (66.90), as well as four

61

aromatic multiplets for the remaining sixteen aryl hydro-
gens. The proton spectrum of the other isomer was almost
identical. The 13C NMR spectrum for each isomer showed only
eleven signals (three aliphatic carbons and eight aromatic
carbons), as required by symmetry.

The oxygen bridges were removed from either isomer
of 111 with hydrochloric acid in acetic anhydride to give

pentiptycene 118. Again its structure was apparent from

 

 

its spectra. The proton spectrum of 118 showed a four-
proton singlet for the bridgehead hydrogens (65.50) and
two singlets, area ratio “:2, for the uncoupled protons of
the central anthracene ring (67.81, 8.06), as well as two
multiplets for the remaining sixteen aryl protons. The
13C NMR spectrum of 118 showed only eight signals as re-
quired by symmetry. The ultraviolet spectrum of 118 in

acetonitrile contained a wealth of absorption bands as a

consequence of the central anthracene moiety, the longest

62

wavelength absorption appearing at 371 nm.

Reaction of pentiptycene 118 with o-benzyne (generated
from o-benzenediazonium carboxylate) gave adduct 119.u2
The structure was assigned from the method of synthesis

and from the spectral data.

 

Attempts to react pentiptycene 118 with any di-aryne
equivalents failed. With tetrabromobenzenes, 11, 19 and
fig, the pentiptycene was recovered quantitatively. Ap-
parently, the temperatures at which these n-butyllithium
reactions must be run (-u0°C to 0°C), were not high enough

to allow the reaction to take place.

63

 

 

 

 

'28 + BUU —> NO REACTION
N
I28 + BUU > NO REACTION

L.

B L'

|28 + Br " U' e7 N0 REACTION
,\J‘ I3?

4.8

Pentiptycene 118 was also reacted with bis-triazole

$89, a new di-aryne equivalent developed by Hart and OK.43

N Pb(OAO
'33 + @an )4» N0 REACTION
I

 

6A

Again, all of the pentiptycene 118 was recovered, along with
a white polymer thought to have structure 111. This polymer

is obtained if the bis-triazole is oxidized by lead (IV)
lI/D I\
L\¢;7

N

 

 

 

“3

tetraacetate in the absence of diene.
The 2,3,6,7-anthradiyne equivalent, bis-adduct 118, was
heated in refluxing xylene with pentiptycene 118. Even

after four days, no product was formed. Here, the oxygen

3 4 DAYS > NO REACTION
'33 + ' O“ XYLENE,A'

onti- I25
N

 

bridges in 118 may have a role in preventing the reaction.
In the least hindered endo-approach, shown in Figure 7,
there would still be a substantial non-bonding interaction
between an oxygen bridge and one of the outer phenyl

rings.

65

 

Figure 7. Endo-approach in Diels-Alder reaction between
bis-epoxide 118 and pentiptycene 118.

B. Synthesis of a Triptycene From a 2,336,7-Naphthadiyne

Equivalent

6,7-Dibromo-l,A—dihydronaphthalene-l,A-epoxide, 111,
synthesized from 1,2,4,5-tetrabromobenzene, 18, and furan
using one equivalent of n-butyllithium, should also be an
effective dienophile. Again, the oxygen bridge in the
resulting cycloadducts should be easily removed to give

an aromatic structure. And, since 111 is functionalized

66

 

 

leq
Br Br n-BuLi A
Br Br 6:0
\
99

with bromines, it can be regarded as a synthetic equiva-

lent of 2,3;6,7-naphthadiyne l%%.

00‘

'33
N

Reaction of epoxide lég with one equivalent of anthra-

cene in refluxing xylene gave the adduct lég (mp 265-266°C)

.,. cos
B 0‘.” XYLENE , A;

|32
r~_/

 

 

in 96% yield. The adduct was identified by its spectra.

The proton NMR spectrum of l§g showed three two-proton

67

singlets for the three sets of aliphatic hydrogens(52.09,
“.26, n.7u), as well as aromatic peaks for the remaining ten
aryl hydrogens. The 130 NMR showed three aliphatic carbons
and nine aromatic carbons, a total of twelve peaks as
required by symmetry. The mass spectrum gave a molecular
ion peak of m/e 480.

Adduct l§g was dehydrated with hydrochloric acid in

acetic anhydride to give the dibromotriptycene lié. Again,
1

the structure was apparent from the spectra. The H NMR

HI.
:34 C’ACZ‘); 3"

 

spectrum of l§§ showed a two-proton singlet (65.50) for
the bridgehead hydrogens, two two-proton singlets for the
uncoupled hydrogens of the naphthalene ring (67.60, 7.93),
and two aromatic multiplets for the remaining eight aryl
protons. The 130 NMR showed only seven peaks. Two peaks
due to quaternary carbons were missing because of the low
solubility of the compound.

Reaction of lég with furan using n-butyllithium to

generate the aryne, was carried out in the manner described

68

for the dibenzyne reactions in Part I. As before, the

structure of adduct lag was apparent from its spectral data.

 

 

The 1H NMR of léé contained two two-proton singlets for
the four bridgehead hydrogens (65.“8, 5.72), and three
two-proton singlets (66.88, 7.65, 7.76) for the three sets

2 hydrogens, as well as two aromatic mul—

of uncoupled sp
tiplets for the remaining eight hydrogens. The 13C NMR
was simpler than predicted by symmetry, only eleven peaks,
because of coincidental overlap of some of the aromatic
peaks. The mass spectrum gave a molecular ion peak of
m/e 370.

Deoxygenation of adduct léé was carried out using low
valent titanium in the same manner as described in Part I.
The novel triptycene til (mp 22l-222°C) was isolated in
79% yield. The spectral data are in agreement with the

1

structure shown. The H NMR spectrum of til consisted

of a two-proton singlet (65.53) for the two bridgehead

69

'TKH .Zn
l36 4)
~ THF, A

w

 

 

hydrogens, and two two—proton aromatic singlets for the

two sets of uncoupled hydrogens of the anthracene moiety
(67.87, 8.22), as well as four multiplets for the twelve
remaining aromatic hydrogens. The 130 NMR contained eleven
peaks (one aliphatic, ten aromatic carbons) as required by
symmetry. The mass spectrum gave a strong molecular ion

peak at m/e 354.

C. Suggestions for Further Studies

Iptycenes are an intriguing class of compounds because
they possess a high degree of symmetry, and they comprise
planar aromatic systems in well-defined orientations to
one another.uu’l45

Heptiptycene lgg has a geometry with several interest-
ing structural features (see Figure 8). Four of the aryl
.rings are arranged in a horseshoe shape which creates a

non-polar or lipophilic cavity with two parallel arene

rings separated by approximately 8.2 A. This cavity might

7O

 

 

Figure 8. End on view of heptiptycene lgg.

trap non—polar small molecules (especially if the three
remaining rings were to carry polar, hydrophilic substi-
tuents), or may yield novel organometallic complexes.
Also, with two additional arene rings, this cavity would
be converted to three-dimensional hexagonal array of
benzenoid rings.

Pentiptycene kég and triptycene £17 supply easy entry
into higher iptycene analogues since both contain an
anthracene ring which can undergo Diels-Alder reactions
with suitable dienophiles. If pentiptycene lgg, for ex-
ample,.could react with a di-benzyne equivalent, the
trideciptycene lQQ would be produced. Here, five aryl

rings on each side of the molecule are arranged so that

71

 

00
IS? Q

only one more arene ring would be needed to form a cyclic
array. So far, as previously discussed, all attempts to

react pentiptycene lgfi with a di-benzyne equivalent have

failed.

72

 

K)
a)
W

2

 

'93

Triptycene lél with a di-benzyne equivalent may yield
two isomers of noniptycene, $82 and %£Q’ one of which would
possess the same arrangement of five aryl rings.

Finally, since pentiptycene lgg reacts with benzyne
generated with o-benzenediazonium carboxylate to give
heptiptycene lgg, it should react in the same way with
a derivative of o—benzenediazonium carboxylate, such as
lfil.u6 This would give dibromoheptiptycene lgg, which
could react further with anthracene or triptycene l§z and
n-butyllithium to yield the novel iptycenes, lag and lgg,

respectively (see Scheme 6).

73

 

I37 >
N

 

EXPERIMENTAL

General Procedures

 

NMR spectra (1H and 13C) were recorded on either a
Bruker WM 250 MHz or a Varian T-6O Nuclear Magnetic Reson-
ance Spectrometer using tetramethylsilane (TMS) as the in-
ternal standard. ESR spectra were measured with a Varian
E-u EPR Spectrometer. IR spectra were recorded on a
Perkin-Elmer Model 167 spectrometer. Mass spectra were
measured at 70 eV by Mr. Ernest Oliver using a Finnigan
AOOO spectrometer with the INCOS data system. Ultraviolet
absorption spectra were recorded on a Varian Carey 219
spectrometer. Melting points were determined using a MEL-
TEMP apparatus, modified when necessary for high tempera-
tures, and are uncorrected. Anhydrous magnesium sulfate
was used as the drying agent throughout, and the silica
gel for chromatography was 230-hOO mesh. Analyses were
performed by either Spang Microanalytical Laboratory,
Eagle Harbor, Michigan or Guelph Chemical Laboratories,

Ltd., Guelph, Ontario, Canada.

9,lO-Dimethoxyoctamethylanthracene,_69

 

28

To a solution of tetrabromo-p-dimethoxybenzene, lg,

(2.27 g, 5.0 mmol) and N,N-dimethylaminotetramethylpyrrole28

75

76

(2 g, excess) in 50 mL tetrahydrofuran under argon at
-78°C was added n-butyllithium (12 mmol in 25 mL hexane)
dropwise over two hours. The reaction was allowed to come
slowly to room temperature, then 1 mL methanol was added,
followed by 50 mL water. The product was extracted into
methylene chloride, washed with water, dried, and the sol-
vent removed.

A waxy, yellow solid remained, which was heated under
vacuum at 180°C for thirty minutes. The black residue
produced was eluted through 8 cm florisil with 1:1 chloro-
form-hexane, and recrystallized from ether-methanol to give
1.05 g (60%) bright yellow crystals, mp 216-218°C (lit.28
218-22000). lH-NMH (CD013): 52.38 (s, 12 H), 2.76 (s,
12 H), 3.33 (s, 6 H). Mass spectrum m/g 350 (M+), 335

(base peak).

Tetrabromohydroquinone,_1Q5.

Bromine (64 mL, 1.2 mol) was added drOpwise to a solu-
tion of hydroquinone (24.2 g, 0.2 mol) in 200 mL acetic
acid cooled in an ice bath. .The dark orange solution was
left stirring overnight after which it was light orange
and contained much white precipitate. A saturated sodium
bisulfite solution was added until the reaction mixture was
colorless, and 65 g (76%) white crystals collected, mp
2M2-2AA°C (lit.u8 2AAOC). Mass spectrum m/g M26 (M+ and

base peak).

77

A2,3,5,6-Tetrabromo-l,flediethoxybenzene,A70

Ethyl bromide (5 mL, excess) was added all at once to a
solution of 145 (10.65 g, 0.25 mol) and potassium hydroxide
(2.8 g) in 30 mL methanol. The resulting solution was re—
fluxed for twenty hours. Then the solvent was removed, and
the residue was taken up in ether (100 mL) and 0.5 N
sodium hydroxide, 0.1 N hydrochloric acid, and brine, and
dried. Removal of the solvent left a tan solid which was
recrystallized from methanol to give 7.2 g (60%) white
needles, mp 150-151°C. Mass spectrum m/g (relative in-

l

tensity) 482 (13), 454 (7), 426 (100), 131 (87). H NMR

(CDC13): 61.45 (t, 6 Hz, 6 H), 4.00 (q, 6 Hz, 4 H).

9,lO-Diethoxyoctamethylanthracene, 71

Synthesis was carried out analogous to 69 from 10
(2.4 g, 5 mmol) and N,N-dimethylaminotetramethylpyrrole28
(2 g). Recrystallization of the crude product from methanol-
water gave 0.95 g (50%) bright yellow needles, mp l7l-l72°C.
1H NMR (toluene-d8): 61.26 (t, 7 Hz, 6 H), 2.32 (s, 12 H),
3.07 (s, 12 H), 3.48 (q, 7 Hz, 4 H). Mass spectrum m/g
(relative intensity) 378 (33), 349 (60), 321 (100), 305
(10), 290 (10), 235 (9), 161 (12). 523;: Calcd for

C26H3402: C, 82.46; H, 9.05. Found: C, 82.45; H, 9.09.

Winn-3*-ml.

78

2,3,5,6-Tetrabromo-l,4-diisoprgpoxybenzene,_72

To a solution of 145 (21.3 g, 0.05 mol) and potassium
hydroxide (5.61 g, 0.10 mol) in 75 mL methanol was added
all at once isopropyl iodide (20.4 g, 0.12 mol). The
brown reaction mixture was refluxed for forty hours after
which the solvent was removed. The residue was taken up
in ether (100 mL) and 0.5 N sodium hydroxide (50 mL).

The organic layer was washed successively with 0.5 N

sodium hydroxide, 0.1 N hydrochloric acid, and brine, and
dried. Evaporation of the solvent gave a dark brown solid
which was eluted through 8 cm florisil with 1:1 chloro-
form-hexanes. The resulting orange solid was recrystal-
lized from methanol to give 10.4 g (41%) pale yellow needles,
mp 104-10500. 1H NMR (00013): 51.40 (d, 6 Hz, 12 H),

4.75 (sept, 6 Hz, 2 H). Mass spectrum m/e 510 (M+), 43

(base peak).

9,lO—Diisopropoxyoctamethylanthracene, 73

Synthesis was carried out analogous to 62 from 72
(2.55 g, 5.0 mmol) and N,N-dimethylaminotetramethylpyrrole28
(2 g). Recrystallization of the crude product from ace-
tone gave l.2 g (60%) small, yellow crystals, mp 218-219°C.
1H NMR (toluene-d8): 51.08 (d, 6 Hz, 12 H), 2.47 (s, 12 H),
3.19 (s, 12 H), 4.12 (sept, 6 Hz, 2 H); 13c NMR (00013):

517.1, 21.0, 22.0, 75.4, 127.7, 127.9, 133.6, 151.4. Mass

79

spectrum: m/e (relative intensity) 406 (8), 363 (5), 321
(100), 305 (7), “3 (50)-
Anal. Calcd for C28H38O2: C, 82.71; H, 9.42. Found:

C, 82.76; H, 9.46.

2,3,5,6-Tetrabromo-4-(bromomethy1)anisole, 146

A solution of methyl tetrabromo-p-cresolatel49 (21.9
g, 0.05 mol) and bromine (16 g, 0.1 mol) in 1000 mL carbon
tetrachloride was irradiated with a high intensity lamp,
and refluxed for three hours. The solution was allowed
to cool, washed with dilute sodium bisulfite, and the sol-
vent removed. The off-white crystals remaining were re-
crystallized from ethanol to give 25.6 g (99+%) white

needles, mp 162-164°C. l

H NMR (CDClB): 63.8 (S, 3 H),
4.8 (s, 2 H). Mass spectrum: m/e (relative intensity)
514 (l), “36 (65), 315 (21), 234 (30), 153 (40), 85 (37):

74 (100).

2,3,5,6-Tetrabromo-4-(acetoxymethyl)anisole,141

To a solution of 146 (20.4 g, 0.04 mol) in 150 mL
acetic anhydride was added potassium acetate (2 g). The
reaction mixture was refluxed three hours, allowed to
cool, then poured into an ice-2N sodium hydroxide mixture.
The light brown precipitate which formed was filtered, and

dissolved in methylene chloride (100 mL). The solution was

80

washed with dilute sodium bicarbonate, water, then dried.
Removal of the solvent left a sandy solid which was re-
crystallized from methanol to give 19.7 g (99+%) white

needles, mp 124-125°C. l

H NMR (00013): 52.1 (s, 3 H),
3.85 (s, 3 H), 5.55 (s, 2 H). Mass spectrum: m/g_(re1a-
tive intensity) no M+, 437 (1), 415 (1), 375 (7), 357 (1),

74 (5), 43 (100).

 

 

253,536-Tetrabromo-4-(hydroxymethyl)anisole,_148 g

 

To a solution of 141 (20 g, 0.04 mol) in 150 mL ethanol
was added 200 mL lN potassium hydroxide. The solution was
refluxed for four hours, then cooled in an ice bath. The
white crystals which formed were collected by vacuum filtra-
tion and recrystallized from acetone to yield 16.7 g (92%)
white needles, mp 172-17300. 1H NMR (00013): 52.2 (br s,

1 H), 3.8 (s, 3 H), 5.15 (s, 2 H). Mass spectrum m/g
(relative intensity) 454 (56), 373 (44), 330 (38), 266
(100), 223 (34), 141 (32), 74 (29).

2,3,5,6-Tetrabromoanisole,74

 

50

A solution of tetra-n—butylammonium permanganate

(4.80 g, 13 mmol) in 50 mL pyridine under argon was added

 

to 148 (4.54 g, 10 mmol) in 50 mL pyridine at room tempera-
ture. The resulting purple solution was heated to 40-50°C

for six hours (solution turned brown). The reaction

81

mixture was cooled to room temperature and poured into

dilute hydrochloric acid containing some sodium bisulfite.

The white precipitate which formed was filtered and recrystal-
lized from methanol to give 2.9 g (70%) small, white needles,

mp 122-12400 (lit.51 120.500). 1

H NMR (CDC13): 63.85
(s, 3 H), 7.7 (s, l H). Mass spectrum m/g (relative in-
tensity) 424 (56), 409 (10), 381 (23), 328 (14), 221 (30),

81 (42), 61 (100).

1,2,3L4,5,6,7,8-Octamethyl-9-methoxyanthracene, 75

 

Synthesis was carried out analogous to 69 from 74
(2.17 g, 5 mmol) and N,N-dimethylaminotetramethylpyrrole28
(2 g). The crude product was eluted through 10 cm silica
gel with 10:1 hexane-chloroform then recrystallized from
acetone-ether to give 0.2 g (20%) bright yellow crystals,

mp 234—23500. l

H NMR (toluene-d8): 62.33 (s, 6 H), 2.36
(s, 6 H), 2.72 (s, 6 H), 3.04 (s, 6 H), 3.40 (s, 3 H),
8.58 (s, 1 H); 130 NMR (00013): 515.92, 17.57, 17.73,
19.33, 62.22, 114.36, 124.57, 127.72, 128.11, 131.17,
132.11, 133.78, 155.36. Mass spectrum m/g (relative in-
tensity) 320 (80), 305 (100), 41 (100).

Anal. Calcd for C23H280: C, 86.20; H, 8.81. Found:

 

C, 86.17; H, 8.66.

82

1,2,3,4,5,6,7,8-Octamethyl-l,4,5,8-tetrahydroanthracene-

1,4;5,8-bis(§poxide)i_lz

 

A solution of n-butyllithium (22 mmol) in 50 mL hexane
was added dropwise over three hours to 1,2,4,5-tetrabromo-
benzene, 40,52 (3.9 g, 10 mmol) and tetramethylfuran,
76,49 (3 g) dissolved in 50 mL dry toluene under argon
at -78°C. The reaction mixture was allowed to come slowly
to room temperature, then 1 mL methanol was added. The
organic layer was washed with water, dried, and the sol-
vent removed. A waxy, yellow solid remained which was
recrystallized from methanol to give 2 g (71%) small, pale

yellow crystals, mp 290—296°c. 1

H NMR (CDC13): 61.60
(s, 12 H), 1.78 (s, 12 H), 6.82 (s, 2 H). Mass spectrum
m/e (relative intensity) 322 (14), 268 (2), 236 (10),

225 (100).

1,5,9,lO—Tetramethyl-l,4,5,8-tetrahydroanthracene-1,4;5,8-

bis(epoxide), 80

To a solution of tetrabromo-p—xylene 11,53 (8.44 g, 20
mmol) and 2-methylfuran, 78, (4.1 g, 50 mmol) in 200 mL
dry toluene under argon at -23°C was added n-butyllithium
(45 mmol in 100 mL hexane) dropwise over three hours.

The reaction mixture was allowed to come slowly to room
temperature and stirred overnight. Methanol (1 mL) was

added, and the mixture was washed with water, dried, and

5..
.5

LE 7"

83

the solvent removed. The yellow waxy solid remaining was
recrystallized with methanol to give 1.8 g (34%) off-white

crystals, mp 248-252°C. l

H NMR (00013): 51.98 (s, 6 H),
2.25 (s, 6 H), 5.50 (d, 2 Hz, 2 H), 6.85 (br s, 2 H), 6.95
(br d, 2 Hz, 2 H). Mass spectrum m/g (relative intensity)
266 (25), 240 (12), 223 (43), 197 (100), 181 (69), 165

(43), 152 (23), 43 (95).

1,8,9,10-Tetramethyl-l,4,5,8-tetrahydroanthracene—l,4;5,8-

 

bis(epoxide)m 7%

After filtering the off-white crystals from the above,
the mother liquor was evaporated to a yellow oil. Re-
crystallization from hexane gave 1.5 g (28%) white crys-

tals, mp 174-180°C. l

H NMR (CDC13) showed this to be a

3:2 mixture of syn and anti isomers. Major isomer: 62.10

(s, 6 H), 2.30 (s, 3 H), 2.38 (s, 3 H), 5.65 (m, 2 H);
6.8-7.1 (m, 4 H); minor isomer: 62.10 (s, 6 H), 2.40 (s, 3 H),
2.45 (s, 3 H), 5.65 (m, 2 H), 6.8;7.1 (m, 4 H). Mass spectrum:
g/g (relative intensity) 266 (19), 240 (13), 223 (23),

197 (46), 181 (37), 165 (27), 152 (15), 85 (26), 43 (100).

9,lO-Diisopropoxy-l,4,5,8—tetrahydroanthracene-l,4;5,8-

 

bis(epoxide), 82

To a solution of 1,4-diisopropoxytetrabromobenzene, 72,

(2.55 g, 5 mmol) and furan, 81,(l g) in 50 mL dry toluene

84

at -78°C under argon was added dropwise over two hours
n-butyllithium (12 mmol in 30 mL hexane). The reaction
mixture was allowed to come slowly to room temperature at
which time 1 mL methanol was added. The mixture was washed
with water, dried, and the solvent removed. The yellow

1

oil remaining was recrystallized from hexane to give 0.45 L

g (60%) white crystals, mp 184-188°C. H NMR shows it to

s- ‘4

be a 1:1 mixture of syn and anti isomers which could not

..__ _

be separated: 61.3 (dd, 7 Hz, 12 H), 4.2 (br sept, 7 Hz, L.
2 H), 5.8 (s, 4 H), 7.1 (s, 4 H). Mass spectrum m/g

(relative intensity) 326 (21), 213 (15), 186 (100), 121

(27); 43 (48).

Diethyl Diglycollate,13231

 

A solution of diglycollic acid (60.0 g, 0.045 mol)
in 250 mL ethanol was treated with ten drops of concentrated
sulfuric acid, and refluxed overnight. After removing the
solvent, the oily residue was distilled under vacuum (97-
100°C, 0.7 Torr) to give 70.3 g (83%) of a clear, viscous

1

liquid. H NMR (CD013): 51.30 (t, 7 Hz, 6 H), 4.23 (q,

7 Hz, 4 H), 4.23 (s, 4 H).

 

Diethyl 3,4-dihydroxyfuran—2,5-dicarboxy1ate,159

To a freshly prepared solution of sodium ethoxide in

ethanol (11.5 g sodium metal in 200 mL ethanol) was added

 

85

diethyl oxalate (17.5 g, 0.12 mol) and 149 (19.0 g, 0.10
mol). The solution was stirred at room temperature for

two hours, then cooled in an ice bath. Neutralization with
2N hydrochloric acid gave 14 g (57%) white crystals, mp
185-600 (lit.5“ 186°C).

Diethyl 3,4-dimethoxyfuran-2,5-dicarboxy1ate, 151

 

To a solution of 150 (19.6 g, 0.14 mol) in 100 mL
acetone was added 28.0 g potassium carbonate and 30.4 g
dimethyl sulfate. The mixture was refluxed with stirring
for two hours, after which additional dimethyl sulfate
(8 g) was added. Reflux was continued for fifteen more
hours, then the hot solution was filtered. After remov-
ing the acetone from the filtrate, the remaining oil was
cooled in an ice bath. Dilute ammonium hydroxide was added
with stirring until a white, waxy precipitate formed. Fil-
tration and recrystallization from hexane gave 18.4 g (85%)
white needles, mp 82-84°C (lit.5u 88-89°C). Mass spectrum;

2/3 272 (M+ and base peak).

3,4-Dimethoxyfuran-255-dicarb0xy11c acid,15§

To a solution of 151 (27.2 g, 0.1 mol) in 27 mL diox-
ane was added 60 mL 1N sodium hydroxide. After five hours
of reflux the solution was cooled, and acidified with di-

lute hydrochloric acid. White crystals (19.9 g, 92%)

86

formed which were filtered and washed with water, mp 250°C

(dec) (lit.514 255-7°C, dec).

3,4-Dimethoxyfuran,§3

 

Five separate reactions were set up as follows:
copper (II) acetate (0.1 g) and powdered c0pper (2 g)
were added to a solution of 152 (10 g, 0.046 mol) in 100
mL freshly distilled quinoline. The mixture was heated
at 170°C for thirty minutes.

The five reaction mixtures were combined for vacuum
distillation. At 110°C and 0.7 Torr, the first 200 mL
were collected (no product was present in later fractions),
and added to 200 mL ether. The organic solution was ex-
tracted five times with 50 mL portions of 2N sulfuric acid
(cooled in an ice bath!!), two times with dilute sodium
bicarbonate, then with water, and dried. The ether was
removed and the remaining yellow liquid was distilled.

The first fraction (61-2°C, 0.7 Torr) contained 15.0 g
pure 83. The second fraction (110°C, 0.7 Torr), a 1:1
mixture of quinoline and 83, was redissolved in ether,
extracted again, and redistilled to give an additional
5.0 g 53. The total yield was 20.0 g (68%) (iit.55 64%).

1H NMR (00013): 53.70 (s, 6 H), 6.90 (s, 2 H).

87

2,3,6,7,9,10-Hexamethoxy-l,4,5,8-tetrahydroanthracene-

1,“;5,8-bis(epoxide), 84

 

To a stirred solution of tetrabromo-p-dimethoxybenzene

28 (4.54 g, 10 mmol) and 83 (2.8 g, 22 mmol) in 100 mL

12:
dry toluene at -78°C under argon was added n-butyllithium

(12 mmol in 30 mL hexane) dropwise over two hours. The
reaction mixture was allowed to come slowly to room tem-
perature after addition. Methanol (1 mL) was added, and

the mixture was washed with water, dried, and the solvent
removed. The remaining brown oil was treated with hexane

to give 2.4 g (65%) small, white crystals, mp 140-155°C

(a 1:1 mixture of nyn and nn£;_isomers). Washing the solid
with methanol dissolved the nyn isomer. The nnni isomer

was collected by vacuum filtration as small, white crystals,
mp 220—222°C (dec). Removal of the methanol left an off-
white oily solid (90% enriched sample of nyn isomer)which
could not be further purified. 1H NMR (00013) (£221)=

63.65 (s, 12 H), 3.80 (s, 6 H), 5.4 (s, 4 H); (EX2)‘

53.70 (s, 12 H), 3.75 (s, 6 H), 5.4 (s, 4 H); 130 NMR

(CDC13) (£221)= 558.97, 60.76, 80.20, 139.31, 143.34,
145.69. Mass spectrum n/g (relative intensity)390 (99),

375 (17), 347 (29), 301 (30), 287 (38), 273 (43), 257

(49), 245 (21), 45 (33).

88

6,7-Dibromo-5,8-dimethyl-l,4-dihydronaphthalene-l,4-

epoxide, 85

To a solution of tetrabromo-p-xylene, %1,49 (4.2 g,

10 mmol) and furan (3 mL) in 100 mL dry toluene under argon
at -23°C was added n-butyllithium (14 mmol in 40 mL hexane)
over two hours. The reaction mixture was allowed to come
slowly to room temperature and stirred overnight. Methanol
(1 mL) was added, and the mixture was washed with water,
dried, and the solvent removed. The off-white solid was
recrystallized from hexane, then methanol to give 1.6 g

(50%) small white crystals, mp l40-142°C. l

H NMR (CDC13):
62.4 (s, 6 H), 5.7 (br s, 2 H), 6.95 (br s, 2H). Mass
spectrum n/g (relative intensity) 330 (10), 304 (18), 221

(100), 141 (78), 115 (75)-

1,9,10-Trimethyl-l,4,5,8-tetrahydroanthracene-l,4;5,8-
bis(epoxide), 86

To a solution of 45 (1.65 g, 5 mmol) and 2—methylfuran
(2 g, excess) in 50 mL dry toluene at -78°C under argon was
added n-butyllithium (5 mmol in 20 mL hexane) dropwise over
two hours. The reaction was allowed to come slowly to room
temperature, and methanol (1 mL) was added. The mixture
was washed with water, dried, and the solvent removed.
The waxy yellow solid remaining (1 g, 80%) was a mixture

Of syn and anti isomers. Treatment with hexane gave one

89

isomer (nyn ?) preferentially as small, off-white crystals,
mp 190-195°C. Removal of the hexane left a yellow oil

(90% enriched sample of other isomer) which could not be
further purified. 1H NMR of crystalline isomer (CD013):
61.90 (s, 3 H), 2.18 (S, 3 H), 2.21 (S, 3 H), 5.60 (br

s, 3 H), 6.95 (br s, 4 H). Mass spectrum n/e (relative
intensity) 252 (29), 226 (13), 209 (16), 197 (41), 181

(100), 165 (59), 152 (23), 43 (l4).

9,lO-Dimethoxyanthracene, 22

To a suspension of 1 mL titanium tetrachloride in 50
mL dry tetrahydrofuran under argon at 0°C was added 1.4 g
zinc powder (excess). The steel gray suspension was heated
to reflux, and a solution of bis-epoxide 4Qu9 (212-2221
mixture) (0.27 g, 1.0 mmol) in 50 mL tetrahydrofuran was
added dropwise (15 minutes). The mixture was refluxed for
eight hours, then cooled to room temperature, and poured
into dilute hydrochloric acid. The resulting purple mixture
was extracted with methylene chloride, and the organic layer
was washed with water, and dried. The remaining yellow
solid was recrystallized from chloroform to give 0.21 g

1H

(90%) yellow plates, mp 198-199°C (lit.56 202°C).
NMR (00013): 54.05 (s, 6 H), 7.30 (m, 8 H), 8.10 (m,

4 H).

90

l,2,3,4,5,6,7,8-Octamethylanthracene, 81

 

Deoxygenation of 11 was carried out in the same manner
and scale as 18' The crude product was recrystallized
from chloroform - hexane to give 0.25 g (80%) small yellow

crystals, mp 292—29400 (lit.39 299-30000). l

H NMR (tol-
uene-d8): 62.30 (s, 12 H), 2.71 (s, 12 H), 8.83 (s, 2 H).

Mass spectrum n/g (relative intensity) 290 (100), 275 (9).

 

1,8,9,10-Tetramethylanthracene,_8,857

Deoxygenation of 19 was carried out in the same manner
and scale as 44, except the reaction was worked up in the
dark. Removal of the solvent left a yellow oil which was
recrystallized from methanol-ether to give 135 mg (57%)

yellow flakes, mp 80-82°C. l

H NMR (toluene-d8): 62.66

(s, 6 H), 2.71 (s, 3 H), 2.79 (s, 3 H), 7.16-7.25 (m, 4 H),
8.02 (d, 2 H). Mass spectrum n/n (relative intensity)

234 (97), 219 (100), 202 (29), 189 (14), 101 (29), 94

(16).

l,5,9,lO-Tetramethylanthracene,_89

Deoxygenation of 89 was carried out in the same manner
and scale as 42, except the reaction was worked up in the
dark. The crude product was recrystallized from methanol

1

to give 0.20 g (85%) yellow needles, mp 71-72°C. H NMR

(toluene—d8): 62.65 (s, 6 H), 2.87 (s, 6 H), 7.14-7.24

91

(m, 4 H), 8.01 (d, 9 Hz, 2 H). Mass spectrum n/g (relative
intensity) 234 (100), 219 (62), 202 (16), 108 (28).
Anal. Calcd for C18H18: C, 92.26; H, 7.74. Found:

C, 92.17; H, 7.84.

9,lO-Diisopropoxyanthracene,94

Deoxygenation of 8% was carried out in the same manner
and scale as 44. The crude product was recrystallized from
methanol to give 0.26 g (88%) yellow needles, mp 122-124°C.
1H NMR (toluene-d8): 51.29 (d, 6.1 Hz, 12 H), 4.49 (sept.
6.1 Hz, 2 H), 7.35 (m, 2.5 Hz, 4 H), 8.45 (m, 2.5 Hz, 4 H).
Mass spectrum m/e (relative intensity) 294 (15), 252 (2),

209 (100), 180 (8), 152 (15), 43 (15).

2,3,6,7,9,10-Hexamethoxyanthracene, 94

Deoxygenation of 44 was carried out in the same manner
and scale as 44. Removal of the solvent left 0.31 g (85%)
of a yellowish solid which was recrystallized from methanol,
mp 26l-62°C. 1H NMR (00013): 54.05 (s, 12 H), 4.04 (s,
6 H), 7.45 (s, 4 H). Mass spectrum n/g (relative intensity)
358 (48), 343 (100), 328 (9), 313 (8), 179 (3).

nnnl. Calcd for C2OH22O6: C, 67.03; H, 6.19. Found:

C, 67.11; H, 6.35“

92

2,3,6,7-Tetrahydroxyanthroquinone,453

A solution of 94 (0.3 g, 0.8 mmol) in 12 mL methylene
chloride was addedtx>boron tribromide (1.5 g, 6 mmol) in
10 mL methylene chloride under argon at -78°C. The solu-
tion was allowed to come slowly to room temperature, stirred
for an additional four hours, then cooled in an ice bath.
Ice-water (mlO mL) was added cautiously, and the brown-
orange crystals which formed were filtered. Recrystalliza-
tion from ethanol gave 0.14 g (67%) bright orange crystals,
mp <330°C (dec.) (lit?9 <330°C, dec.). Mass spectrum n/g
(relative intensity) 272 (45), 258 (100), 240 (16), 229

(37), 212 (22), 184 (18).

l,9,lO-TrimethylanthraceneL 933:

Deoxygenation of 44 was carried out in the same manner
and scale as 18’ except work—up was carried out in the
dark. The crude product was sublimed at 30°C and 0.7
torr to give 0.17 g (80%) yellow needles, mp 76-78°C.
1H NMR (00013): 52.75 (s, 3 H), 2.8 (s, 3 H), 2.95 (s,

3 H), 7.2 (m, 4 H), 7.8 (m, 3 H). Mass spectrum n/g
(relative intensity) 220 (100), 205 (47), 189 (11), 178
(8), 101 (8).

a:
2.

AV

o.
'1'

,
M

bron

~n1u
a

stir

0001

en
DU
1!.

a 6
M:
W

O

‘lk\
,

‘1‘

i

y

p

 

93

4,5-Dibromo—3,6-diiodoveratrole, 96

 

A solution of 4,5-dibromoveratrole58 (18 g, 0.61 mol)
and mercuric oxide (42 g) in 160 mL trifluoroacetic acid
was heated to reflux for four hours. The reaction mixture
was cooled in an ice bath, and the white solid (4,5-di-
bromo-3,6-di-(trifluoroacetatomercurio)veratrole) which
formed was filtered.

The crude solid was heated at 70-75°C with iodine (60 g)
and potassium iodide (40 g) in 200 mL water (mechanical
stirrer) for eight hours. After the reaction mixture was
cooled, the solid was filtered, and taken up into chloro-
form. The organic solution was washed successively with
10% sodium thiosulfate, dilute sodium bicarbonate, and
water, dried, and the solvent removed. The off-white
solid remaining was recrystallized from chloroform-methanol
to give 26.4 g (79% from 4,5-dibromoveratrole) white needles,
mp 144-145°C. Mass spectrum n/g (relative intensity) 532
(25), 504 (21), 489 (l4), 405 (5), 390 (15), 254 (l3),

203 (53), 155 (61), 127 (100), 104 (42), 76 (54)-

9,10-Dimethoxyoctamethyl-l,4,5,8-tetrahydrophenanthrene-

1,4L5,8-bis(epoxide)3_,2,7,

 

To a solution of 24 (1.37 g, 2.5 mmol) and tetramethyl-
furan, 1639(1 g, 8 mmol) in 50 mL dry ether was added n-

butyllithium (9 mmol in 50 mL hexane) dropwise over four

at
«M.

.U

A:

‘70

GU
Cu

«14

fro

nee

 

94

hours. The reaction mixture was allowed to come to room
temperature and stirred overnight. Methanol (1 mL) was
added, and the mixture was washed with water, dried, and
the solvent removed. A light yellow oil remained which

could not be purified. l

H NMR (00013); 51.65 (s, 6 H),

1.80 (s, 6 H), 1.85 (s, 6 H), 1.86 (s, 6 H), 3.75 (s, 6 H).
Mass Spectrum n/g (relative intensity) 382 (10), 339 (100),
328 (29), 296 (85), 285 (50), 281 (79), 165 (45), 123 (87),

71 (89).

9,lO-Dimethoxyoctamethylphenanthrene,»98

 

Deoxygenation of the crude oil, 21, was carried out in
the same manner as 18' The crude product was recrystallized
from methanol to give 0.22 g (25% from 94) light yellow

needles, mp 187-188°C. l

H NMR (00013): 52.30 (s, 6 H),

2.36 (s, 6 H), 2.41 (s, 6 H), 2.80 (s, 6 H), 3.86 (s, 6 H);
130 NMR (00013): 16.78, 16.98, 18.05, 20.82, 60.10, 118.50,
127.20, 131.31, 131.94, 134.08, 146.20. Mass spectrum n/g
(relative intensity) 350 (53), 307 (100), 292 (16), 277

(12), 175 (16), 160 (18), 131 (19).

Anal. Calcd. for C24H C, 82.24; H, 8.62. Found:

3002‘
C, 82.12; H, 8.75.

95

General Procedure for Photolysis of Anthracenes and Phen-

 

anthrenes

 

The arene to be photolyzed (10-12 mg) was dissolved in
0.5 mL benzene-d6, placed in a 5 mm NMR tube and flushed with
nitrogen. Irradiation of the sample for 60-90 minutes using
a Hanovia 450 W medium pressure lamp with Pyrex filter was
carried out by taping the sample tube directly to the water-
cooled Jacket of the lamp.

All of the anthracenes and phenanthrenes discussed
were irradiated first at room temperature, then at -78°C.

For the low temperature runs, toluene-d8 was substituted

for benzene—d6 as solvent. The lamp and cooling Jacket
along with the sample were immersed in a dry ice-isopropanol
bath, and dry nitrogen was passed through the cooling
jacket.

After irradiation, the sample tube was immediately trans—
ferred to the WM 250 NMR spectrometer, pre-set at a suitable
temperature between -60°C and room temperature, and the
spectrum was recorded. The results are presented in the

text.
Irradiation of 1,5,9,10-tetramethylanthracene,49, in the
Presence of Oxygen

The reaction was carried out in the same manner as des-

cribed for the room temperature photolyses of arenes,

96

except the sample was undegassed. After irradiating for

1H NMR

30 minutes, the endoperoxide 44% was produced.
(benzene—d6): 61.96 (s, 6 H), 2.09 (s, 6 H), 6.75-7.01
(m, 6 H); 13c NMR (benzene-d6): 518.56, 21.87, 81.24,
119.66, 126.91, 131.53, 131.88, 143.80 (a sixth aromatic
peak must fall coincidentally under the solvent peak).

Mass spectrum n/g (relative intensity) 266 (4), 234 (100),

219 (32), 85 (22), 40 (16).

 

Irradiation of 1,8,9,lO-tetramethylanthracene,48, in the

Presence of Oxygen

 

Photolysis of an undegassed sample of 44 for thirty

minutes produced endOperoxide $44. 1

H NMR (benzene-d6):
61.79 (S, 3 H), 1.99 (S, 3 H), 2.07 (s, 6 H), 6.71-7.06
(m, 6 H). Mass spectrum n/n (relative intensity) 266 (4),

251 (9), 234 (100), 219 (36), 85 (20)-

Reaction of Octamethylanthracene_81 with TFA

 

To a solution of octamethylanthracene 41 (6 mg, 0.02
mmol) in 0.5 mL chloroform-d was added 0.02 mL of 1M tri-
fluoroacetic acid in chloroform-d. Immediately, the solu-

tion turned a deeper shade of yellow. The l

H NMR spectrum
of 84 disappeared, and an ESR signal (shown in Figure 6a)
was observed. After no change in the spectra of the sample
for one hour, the solution was quenched with water. The 1H

NMR of octamethylanthracene 81 reappeared unchanged.

97

 

 

Reaction of 9—methoxyoctamethylanthracene 28 with TFA

The experiment was carried out in the same manner and

1

scale as 88. Initially, the H NMR spectrum was wiped

out, and a weak ESR signal (Figure 6b) appeared. After
several hours, a new 1H NMR spectrum appeared. After quench-
ing with a few drOps of water, the solvent was removed,

leaving an off-white residue. This was recrystallized from

methanol to give 4 mg (70%) white solid, mp 245-248°C.

 

The spectral data of this solid are consistent with that

1

of the octamethylanthrone 448 (lit.39 mp 251-252°C). H

NMR (CD013): 52.28 (s, 6 H), 2.31 (s, 6 H), 2.35 (s, 6 H),

2.54 (s, 6 H), 3.56 (s, 2 H). IR spectrum (CHCl3): 820

l ’1 (m),.l450 cm"l (m),

-1

cm“1 (m), 1160 cm’
1

(w), 1320 cm

-1

1580 cm- (m), 1655 cm (s), 1670 cm (s), 2960 cm'1 (s).

Mass spectrum m/e (relative intensity) 306 (86), 291 (100).

Reaction of 9,10-dimethoxyoctamethylanthracene 84 with TFA

The experiment was carried out in the same manner as 88.
On addition of trifluoroacetic acid, the solution turned
dark blue. But the color faded in an instant to pink, and
a new 1H NMR spectrum appeared. Quenching with water, and
removal of the solvent gave a pink residue. Fractional re-
crystallization of the residue with acetone gave first 8428
(mp 278-280°C), then 8428 (mp 290-292°C), both as white

crystalline solids. (The yield of each product determined

98

by integration of the l

H NMR was 60% 4888 and 40% 1488.
Much product was lost in the isolation).

For 1128 - 1H NMR (00013): 52.28 (s, 1 H), 2.51 (s, l H);
130 NMR (00013): 516.90, 17.19, 49.15, 133.29, 134.14,
136.79, 140.73. IR spectrum (CHC13): 880 cm“1 (m), 1240

l (m), 3025 cm"1 (m). Mass spectrum: n/g

cm.1 (s), 1410 cm—
320 (32), 305 (100), 290 (24), 277 (10).

For $128 - 1H NMR (CDC13): 51.35 (s, 6 H), 1.94 (s,
6 H), 2.20 (s, 6 H), 2.49 (s, 6 H), 4.51 (s, l H). IR
spectrum: 1280 cm'1 (m), 1340 cm-1 (m), 1680 cm-1 (s),

1

2940 cm- (s), 3690 cm.1 (br). Mass spectrum n/n (relative

intensity) 305 (100), 291 (7)..

1,4,5,8-Tetrahydroanthracene-l,4;5,8—bis(epoxide), 848

To a stirred solution of 1,2,4,5-tetrabromobenzene,
48,52 (3.94 g, 10 mmol) and furan (10 ml) in dry toluene
(200 mL) at -23°C under argon was slowly added (4 h) n-
butyllithium (7.7 mL, 12 mmol, of a 1155 M solution in
hexane diluted with 200 mL of dry hexane). After addition
the mixture was slowly allowed to warm to room temperature.
Methanol (1 mL) was added cautiously and the mixture was
stirred for a few minutes. The organic layer was washed
with water and dried. Solvent removal under reduced pres-
sure gave a gummy yellow solid which partially dissolved
on addition of methanol (10 mL). The off-white crystals

which remained (0.7 g) were recrystallized from acetone to

99

give small white plates of the anti isomer, mp (dec) 245°C.
The methanol solution was evaporated to dryness and the
residue was recrystallized from ethyl acetate-hexane, then

from methanol to give the pure syn isomer (0.8 g), mp

1H

191-193°C. The total yield of both isomers was 71%.
NMR (00013) (anti): 55.62 (s, 4 H), 7.01 (s, 4 H), 7.18
(s, 2 H); 13c NMR (00013) (£231): 582.23, 113.75, 143.30,
147.69; the NMR spectra of the syn isomer were virtually

identical with those of the anti isomer (differences of

P‘.‘ {.flmmm

0.01 in the proton spectrum and 0.10 in the carbon spectrum).
Mass spectrum (anti) m/g (relative intensity) 210 (43),

184 (26), 181 (13), 156 (34), 155 (63), 154 (31), 153 (100),
152 (73), 151 (18), 128 (22), 127 (13), 126 (10), 87 (12),

85 (29). Anal. (anti): Calcd. for C14H1oo2‘ c, 80.0;

H, 4.76. Found: C, 79.95; H, 4.87.

Adduct of Anthracene and bis-epoxide 125_(121)

A solution of bis-epoxide 125 (anti isomer) (2.1 g,
10 mmol) and anthracene (3.6 g, 20 mmol) in xylene (100
mL) was heated at reflux for 48 h. The reaction mixture
was cooled to room temperature and the resulting white
precipitate was collected (4.6 g, 80%) as a mixture of
121 and a trace amount of unreacted anthracene. The latter
was removed by sublimation to give pure 127, mp 440°C
(dec). 1

4.82 (s, 4 H), 6.90 (s, 2 H), 6.98 (m, 4 H), 7.11 (m, 4 H),

H NMR (00013): 52.13 (s, 4 H), 4.36 (s, 4 H),

7.19 (m, 4 H), 7.26 (m, 4 H); 13c NMR (00013): 547.48, 48.80,

81.00.,

145.6.

191 (

stere

OJ
0/

2C
2

all

in
aci
ac)

 

 

100

81.09, 110.08, 123.50, 123.68, 125.70, 125.97, 141.49, 144.25,
145.61; mass spectrum, n/n (relative intensity) 566 (6),
530 (21), 375 (50), 370 (65), 326 (17), 339 (15), 203 (13),
191 (43), 178 (100), 44 (43).

Analogous reaction of nynflgé with anthracene gave a

stereoisomer of 127 in 60% yield; mp 395°C (dec); 1H NMR

‘ ~

(CDClB): 62.13 (S, 4 H), 4.35 (s, 4 H), 4.80 (s, 4 H),
6.90 (s, 2 H), 6.98 (m, 4 H), 7.12 (m, 4 H), 7.18 (m, 4 H), ,

if. (in: .

7.26 (m, 4 H); 130 NMR: 547.47, 49.07, 81.18, 110.04, 123.42,
123.70, 125.66, 126.0, 141.34, 144.19, 145.79.

Pentiptycene,_l§8

A suspension of 127 (nyn or nnEi) (800 mg, 1.4 mmol)
in acetic anhydride (20 mL) and concentrated hydrochloric
acid (4 mL) was heated at reflux for 8 h. The cooled re-
action mixture was poured into 200 mL of ice-water and
the resulting light yellow crystals were extracted with
chloroform. The organic layer was washed successively
with water and saturated sodium bicarbonate, and dried.
Removal of the solvent gave a light yellow residue which
was recrystallized from tetrahydrofuran and methanol to
give 300 mg (41%) of pentiptycene as small, white plates,
mp >500°c. 1H NMR (00013): 55.50 (s, 4 H, bridgehead
protons), 7.02 (m, 8 H), 7.40 (m, 8 H), 7.81 (s, 4 H),
8.06 (s, 2 H); 130 NMR (00013): 553.81, 121.34, 123.81,

125,11, 125.71, 130.58, 140.80, 144.40; UV (CH3CN): Amax

a
fv

#b
.nnhs.

bromc

the

all

 

 

101

371 nm (e 6540), 353 (8830), 336 (7150). 320 (4240), 306
(2030), 284 (212, 000), 272 (81,270), 266 (60,500), 260
(61,600), 243 (23,200). Anal. Calcd for Cu2H26: c, 96.98;

H, 4.90. Found: C, 96.46; H, 4.98.

Attempted Reaction of Pentiptycenelgg with 1,2,4,5-tetra-

bromobenzenes,4_17, 19 and 40

 

To a solution of 128 (0.7 g, 1.3 mmol) and 11, 19 or
40 (1 mmol) in 200 mL dry tetrahydrofuran at -23°C under
argon was added n-butyllithium (1 mmol in 20 mL hexane)
dropwise over two hours. The reaction mixture was allowed
to come slowly to room temperature, and methanol (1 mL)
was added. The mixture was washed with water, dried and
the solvent removed. The white solid remaining (~0.7 g) in

all cases was found to be unreacted pentiptycene 128.

Attempted Reaction of Pentiptycenelgé with Diaryne Pre-
cursor 130

Lead (IV) tetraacetate (265 mg, 0.6 mmol in 50 mL
tetrahydrofuran) was added all at once to a solution of
pentiptycene 128 (350 mg, 0.66 mmol) and bis-triazole 130
(57 mg, 0.3 mmol) in 50 mL tetrahydrofuran under argon at
room temperature. The reaction mixture was stirred for
thirty minutes at room temperature. A white solid (50

mg) formed which was filtered. .This solid was insoluble

.A

‘

f.
S

l .9.

I
q

 

.Av‘
0‘.
-

ea
I’e
tu

.. n. I“. . I 44 .fi .1 . u ‘0 fi" ..r.\ u I
7 “ a n. w. M: d_ .. S 71 Ad“ C ». ..._
«I. . w; e n u & M. :. , G» unififiu +b ml.
2. t .20. 3.. . t 0
VA .. L. ‘IP
0. . r5

31.
a“
re
r
r

6

 

 

102

in all normal organic solvents_as well as water, and did
not melt below 500°C.

The mother liquor was diluted with water (50 mL) and
extracted into ether. The organic layer was washed with

water and brine, and dried. Removal of the solvent left

320 mg pentiptycene 128.

Attempted Reaction of Pentiptycenenng with Bis-epoxide

125 (anti)

A solution of pentiptycene 128 (53 mg, 0.1 mmol) and
anti-125 (12 mg, 0.05 mmol) in 20 mL xylene was stirred at
reflux for four days. Removal of the solvent left a white

1

residue (65 mg) shown by H NMR to be a mixture of un-

reacted 125 and 128.

6,7-Dibromo-l,4—dihydronaphthalene-l,fleepoxide,13%

To a stirred solution of 1,2,4,5-tetrabromobenzene,
49,52 (8 g, 10 mmol) and furan, 81, (10 mL) in 200 mL dry
toluene at -23°C under argon was added n-butyllithium (22
mmol in 200 mL hexane) dropwise over three hours. The
reaction mixture was allowed to come slowly to room tempera-
ture after addition. Methanol (1 mL) was added, and the
mixture was washed with water, dried, and the solvent re-
moved. The remaining yellow, oily solid was treated with

hexane to give 4.1 g (70%) small crystals, mp 115-ll7°C

103

(methanol). 1

H NMR (00013): 55.64 (s, 2 H), 6.98 (s,
2 H), 7.45 (s, 2 H); 130 NMR (00013): 581.76, 120.61,
125.43, 142.68, 150.19. Mass spectrum n/n (relative

intensity) 302 (9), 276 (19), 193 (100), 113 (46), 87

(21), 63 (25).

 

Adduct ofy132 and Anthracene(13gl

A solution of epoxide 132 (1.5 g, 5 mmol) and anthra-
cene (l g, 5.6 mmol) in 50 mL xylene was heated at reflux
for 72 hr. The reaction mixture was cooled, and 50 mL
hexane was added. A light tan solid formed which was col-
lected and washed with hexane. Recrystallization of the
solid from tetrahydrofuran and methanol gave 2.3 g (96%)

small, off-white crystals, mp 265—266°c. l

H NMR (CDCl3):
62.09 (s, 2 H), 4.26 (s, 2 H), 4.74 (s, 2 H), 7.02 (m,

2 H), 7.06 (m, 2 H), 7.11 (m, 6 H); 13c NMR (00013):

547.21, 48.45, 80.82, 123.61, 123.81, 124.17, 125.31, 125.9,
126.17, 128.17, 141.10, 143.84. Mass spectrum n/g_(rela-
tive intensity) 480 (4), 462 (l), 302 (2), 289 (7), 276

(9), 203 (26), 191 (100), 178 (53).

3,4—Dibromo:L2Pl.lltriptycenea_%%§

A suspension of 134 (200 mg, 0.4 mmol) in acetic an-
hydride (10 mL) and concentrated hydrochloric acid (2 mL)
was heated at reflux for 24 hrs. The cooled reaction mix-

ture was poured into 200 mL ice-water, and the resulting

104

light brown solid was extracted with methylene chloride.
The organic layer was washed successively with water and
saturated sodium bicarbonate, and dried. Removal of the
solvent gave a light brown residue which was recrystal-
lized from tetrahydrofuran and methanol to give 110 mg
(57%) of 135 as small, off—white crystals, mp 386-388°C

(dec.). 1

H NMR (00013): 55.50 (s, 2 H), 7.02 (m, 4 H),
7.41 (m, 4 H), 7.60 (s, 2 H), 7.93 (s, 2 H); 130 NMR
(CDC13): 053.62, 120.58, 123.84, 125.78, 131.64, 144.02,
155.16 (lacks two peaks due to quaternary carbons because

of low solubility of compound).

Adduct of 135_spd Furan (139)

 

 

To a stirred solution of 135 (250 mg, 0.54 mmol) and
furan, 81, (2 mL) in 100 mL dry tetrahydrofuran at -78°C
under argon was added n-butyllithium (2 mmol in 100 mL
hexane) dropwise over two hours. The reaction mixture was
allowed to come slowly to room temperature after addition.
Methanol (1 mL) was added, and the mixture was extracted
with methylene chloride, washed with water, dried, and the
solvent removed. The remaining yellow residue was recrystal-
lized from methanol to give 140 mg (71%) small, light yellow

crystals, mp 188-190°C. l

H NMR (00013): 55.48 (s, 2 H),
5.72 (s, 2 H), 6.88 (s, 2 H), 7.01 (m, 4 H), 7.41 (m, 4 H),
7.65 (s, 2 H), 7.76 (s, 2 H); 130 NMR (00013): 553.92,

81.88, 118.37, 121.64, 122.17, 123.70, 125.52, 125.61,

105

127.43, 141.75, 145.82. Mass spectrum n/n (relative in-
tensity) 370 (l), 341 (l), 303 (l), 170 (2), 149 (4), 84
(5), 40 (100).

[381.1J-Triptycene, 137

Deoxygenation of 136 was carried out in the same manner
and scale as 10. The crude product was recrystallized
from tetrahydrofuran and methanol to give 280 mg (79%)

small off-white crystals, mp 221-222°C (dec). 1

H NMR (CDCld):
55.53 (s, 2 H), 7.04 (m, 4 H), 7.38 (m, 2 H), 7.44 (m,
4 H), 7.87 (s, 2 H), 7.91 (m, 2 H), 8.22 (s, 2 H); 130
NMR (CDC13): 653.65, 121.31, 123.81, 124.96, 125.61, 125.75,
127.99, 130.52, 131.69, 141.10, 144.19. Mass spectrum
n/n (relative intensity} 354 (100), 353 (66), 278 (3),

176 (69).

BIBLIOGRAPHY

10.

11.

12.

13.

l4.
15.

BIBLIOGRAPHY

For a review, see Hoffmann, R. w. Dehydrobenzene and
Cycloalkynes, Academic Press, New York (1967).

 

 

Fields, E. K.; Meyerson, S. Adv. Phys. Org. Chem.
1284: 6, 18-21.

gittig, G.; Harle, H. Justus Liebigs Ann. Chem. 1989
23, 17.

 

 

Cragg, G. M. L.; Giles, R. G. F.; R005, 0. H. P.
J. Chem. Soc., Perkin I 1918, 1339.

Stringer, M. B.; Wege, D. Tetrahedron Lett. 1989,
21, 3832.

Hart, H.; Lai, C.-Y.; Nwokogu, G.; Shamouilian, 8.;
Teuerstein, A.; Zlotogorski, C. J. Am. Chem. Soc.

1989, 192, 6649.

Sy, A.; Hart, H. J. Org. Chem. 1919,l44, 7.

Hart, H.; Nwokogu, G. J. Org. Chem., 1981, 46, 1251.

 

Egrt, H.; Shamouilian, S. J. Org. Chem. 1981, 46,
74.

 

 

Lehoullier, C. S.; Gribble, G. W. J. Org. Chem. 1988,
48, 1682.

Hart, H.; Shamouilian, S.; Takehira, Y. J. Org. Chem.
1981, 4§_, 4427.

Skvarchenko, V. R.; Shalev, v. K. Dokl. Akad. Nauk.
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Cadogan, J. I. G.; Harger, M. J. P.; Sharp, J. T.
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106

16.

fill
11

dd

ad

 

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.
28.

29.

30.

31.

107

Franck, R. W.,Mande11a, W. L. ; Falci, K. J. J. Org.
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Pritschins, W.; Grimme, W. Tetrahedron Lett. 1989,
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Yang, N. C.; Carr, R. V.; Li, E.; Mcvey, J. K.;
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Cowan, D. 0.; Drisko, R. L.; Elements of Organic Photo-
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Fritsche, J. J. Prakt. Chem. 86 , 101, 333; 86
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Calas,R .; Lalande,R . Bull. SOC. Chim. Fr. 1989,

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Chapman, 0. C.; Lee, K. J. Org. Chem. 1989, 95, 4166.

 

Hart, H., unpublished results.

Lai, C.-Y., Ph.D. Thesis, Michigan State University,
1981.

Low valent titanium produced from zinc and titanium
tetrachloride has been used successfully to reduc-
tively couple carbonyl compounds: Makaiyama, T.;
Sato, T.; Hanna, J. Chem. Lett. W191 1041; and to
reduce sulfoxides: Drabowicz, J.; kolajczyk, M.
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Best, W. M.; Collins, P. A.; McCulloch, R. K.; Wege,
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For papers dealing with strain in 4,5-dimethylphen-
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32.

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34.

32.

33.
34.

35.

36.

37.

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108

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Jiang, J. B.—C., Ph.D. Thesis, Michigan State University,
1975.

 

 

 

Synthesized by Y. Takehira, unpublished results.

Bowden, B. F.; Cameron, D. W. J. Chem. Soc., Chem.
Comm. 1911, 77-

Reduction potentials of series of anthracenes increase
almost linearly with the amount of alkyl substitu-
tion regardless of the position.36 Although there

is no similar compilation of oxidation half-wave po-
tentials, it follows that the E1/2 would decrease
similarly along the same series.

 

 

Klemm, L. H.; Kohlik, A. J.; Desai, K. B. J. Org.
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Sullivan, P. D.; Menger, E. M.; Reddoch, A. H.;
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Nemoto, F.; Ishizu, K. Chem. Phys. Lett. 1981, 84,
44; Gerson, F.; Kaupp, G.; Ohya- Nishigichi,
Angew. Chem. Int. Ed. Eng1.1911,1§_, 657

 

 

Backer, H. J.; Strating, J.; Hiusman, L. H. H.
Rec. Trav. Chim. 1999, 99, 761.

 

Wittig, G.; Harle, H.; Krauss, E.; Niethammer, K.
Chem. Ber. 1999, 99, 951.

 

 

See also: Wolthius, E. J. Org. Chem. ,2215;
Wittig, G.; Steinhoff, G. Chem. JBer. ,‘;5, 203;
Fieser L. F. ; Haddadin, M. J. hem. Soc.

 

1994, 86, 2081; Parham, M. E. Frazer, M. G. ; Bradsher,
. J. Org. Chem. 1911, 37, 358; Sasaki, T.
Kanematsu, K.; Hayakawa, K. —J. Chem;Soc;, Perkin I,
1911, 1951; Sasaki, T. ,Kanematsu, K.; Hayakawa,
Uchide, M. Ibid 19 2750, Wittig, G.; Reuther,
W.‘ Liebggs Ann. Chem. 11; 761, 20; Sasaki, T.;
Kanematsu, K.; Hayakawa, Kondo, A. J. Org. Chem.
1919,38 4100; Bremmer, J. B.; Hwa, Y.;*Whittle, C. P.;
ust J— Chem. 1 14, 91, 1597; Sasaki, T.; Kanematsu,
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42.

43.
44.

45.
46.

47.
48.

49.

50.

51.

52.

53.

54.

55.

56.
57.

109

Sasaki, T.; Kanematsu, K.; Iizuka, K.; Izumichi, N.
Tetrahedron1W19 32, 2879; Tochtermann, W.; Malchow,
A.; Timm,H hem. —Ber. 1919, 111, 1233, Mori, M.;
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kfiék: 1259-

Independent results by N. Raju.

 

 

 

Hart, H.; Ok, D., unpublished results.

Lipczynska—Kochany, E.; Iwamura, H. Chem. Lett.

1991, 1075.

Godfrey, R. J. Chem. Soc., Perkin II, 1918 1019.

 

Attempts in this laboratory to synthesize 141 have to
date failed! A report in the literature CIETming to

have made 2- amino- 4 ,5 dibromobenzoic acid (from which
141 can be made) by direct bromination of anthranilic
a—id is in error.“

J. Indian Chem. Soc. 1919, 56, 1237.

 

Sarauw, Justus Liebigs Ann. Chem. 1919, 209, 125.

 

ngkogu, G. Ph. D. Thesis, Michigan State University,
19 l.

 

Sala, T.; Sargent, M. V. Chem. Commun. 19 , 253;
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McOmie, W. F. W.; Harrisons, C. R. J. Chem. Soc.

191 LQQQ, 997.

Scheufelen, A. Justus Liebigs Ann. Chem. 1QL9, 231
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Shamouilian, 8., Ph. D. Thesis, Michigan State Uni-
versity, 1981. '

 

 

 

McDonald, E.; Suksamrarn, A.; Wylie, R. J. Chem. Soc.,

 

Perkin I, 1911, 1893.
Iten, P.; Hofmann, A.; Eugster, C. Helv. Chim. Acta,

1919, 61, u3o.

Meyer, K. H. Liebigs Ann. Chem. 1911, 319, 37.

 

Attempts to synthesize 99 by another group failed.314

The authors reported that they were only able to

58.

59.

110

isolate tautomer %%§.

H
Ll§

Tautomer % (20%) was detected by NMR in crude fig
in the method of synthesis reported here.

Underwood, H. W.; Baril, O. L.; Toone, G. C. J. Am.
Chem. Soc. ggég, fig, 4087.

 

Boldt, P. Chem. Ber. &géz, 100, 1270.

 

 

   

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