Fine tuning the outcome of 1, 3-dipolar cycloaddition reactions of benzimidazolium ylides to activated alkynes. Issue 19 (12th May 2016) - Georgescu, Emilian
Abstract: 1, 3-Dipolar cycloaddition reactions of benzimidazolium ylides, generated from 3-phenacylbenzimidazolium bromides, to non-symmetrical activated dipolarophiles in various reaction conditions led to complex mixtures of pyrrolo[1, 2- a ]benzimidazole and pyrrolo[1, 2- a ]quinoxaline derivatives. In order to explain all experimental results, the influence of reaction conditions on the reaction products was investigated. For the first time, 4-hydroxy-4, 5-dihydropyrrolo[1, 2- a ]quinoxaline derivatives6, pyrrolo[1, 2- a ]quinoxalinium quaternary salts8, as well as 4-methoxy-4, 5-dihydropyrrolo[1, 2- a ]quinoxalines9, were separated, fully characterized and their interconversions are presented, together with a proposed reaction mechanism. Graphical abstract: