In(III)-TMSBr-catalyzed [2+2] cycloaddition and dearomatization cascade reaction of aryl alkyne and acrylate
Date of Issue2017
School of Physical and Mathematical Sciences
Given the relatively weak strength of indium salts as Lewis acids, trimethylsilyl halides or other silane derivatives are often employed together with In(III) salts as robust combined Lewis acid catalysts. This thesis focuses on the development of novel organic reactions using In(III)-TMSBr catalyst system. A novel example of In(tfacac)3-TMSBr-catalyzed [2+2] cycloaddition reaction of aryl alkynes with acrylates that afford cyclobutenes with aryl and ester substituents in moderate to good yields is developed. Moreover, selective cleavage of C-C/C=C bond of cyclobutene products is also attained to give synthetically useful 1,4- and 1,5-dicarbonyl compounds. Furthermore, a novel In(tfacac)3-TMSBr-catalyzed cascade dearomatization reaction of aryl alkyne with acrylates is also studied for efficient assembly of densely functionalized polycyclic ene skeletons with high stereocontrol. Mechanistic studies conducted aid in elucidation of a plausible mechanism involved for this serendipitously discovered reaction. Using In(III)-TMSBr catalyst system, the synthesis of 1,5-di-bromo-1,4-pentadienes, 1,3,5-triaryl benzenes as well as [4+2] cycloaddition of ɑ-aryl vinyl bromide with methyl acrylate are also demonstrated.