Regioselective oxidative cross-coupling of benzo[d]imidazo[2,1-b]thiazoles with styrenes: a novel route to C3-dicarbonylation.

A novel I2 promoted, highly efficient metal-free and peroxide-free greener domino protocol for the C3-dicarbonylation of benzo[d]imidazo[2,1-b]thiazoles (IBTs) with styrenes has been developed via oxidative cleavage of the C(sp2)-H bond, followed by C3-nucleophilic attack of IBT and oxidation. Interestingly, under these conditions 2-(benzo[d]imidazo[2,1-b]thiazol-2-yl)aniline gave the benzo[4',5']thiazolo[2',3':2,3]imidazo[4,5-c]quinoline derivative via oxidative cleavage of the C(sp2)-H bond, followed by Pictet-Spengler cyclization and aromatization. This method offers the advantages of broad substrate scope, ecofriendly feature and high atom economy apart from higher yields.