In this doctoral research, focus has been on the development of the new chiral Brønsted acid catalysts, large-scale synthesis, novel reaction methodologies and understanding their mechanisms by experimental/computational analysis. In due course of time, a pool of unprecedented chiral Brønsted acid catalysts known to be "BOROX" catalysts, were prepared and characterized by NMR spectroscopy and X-ray analysis. These Wulff's BOROX catalysts were then employed on a variety of asymmetric reactions. In particular, the long-lasted problem of the alkyl aziridination has been solved by the development of the first multi-component aziridination reaction using the IMINO-BOROX catalyst. Out of the investigations regarding alkyl aziridination, a novel multi-component asymmetric [3+2] cycloaddition has also been developed. Additionally, an asymmetric epoxidation of aldehydes utilizing an unprecedented chiral SULFOX-BOROX catalyst has been successfully realized. By means of 1H, 11B NMR and computational analysis, the catalytic cycle of a Brønsted acid catalyzed reaction and its intermediates have been characterized using the Wulff aziridination reaction as the template. Interestingly, during this doctoral research, it has been found that the Brønsted acid catalysts derived from chiral borate anions are generated only upon the addition of a base. This was further supported by NMR spectroscopy, computational chemistry and X-ray analysis. Lastly, a new mechanism has been examined for the imino-aldol reaction using computational chemistry. This mechanism supports the idea of a Lewis acid assisted Brønsted acid catalyzed reaction.
Read
