Construction of Azepino[2,3- b]indole Core via Sulfur Ylide Mediated Annulations.

A novel [4 + 3] annulation of indoline-based aza-dienes and crotonate-derived sulfur ylides is described. This method could be further expanded by using more efficient synthetic strategies, including three-component [3 + 1 + 3] cascade and the direct sulfide-catalyzed [4 + 3] cyclization. These protocols enable the rapid construction of azepino[2,3- b]indole cores, and a broad spectrum of the desired products with diverse substituents was facilely accessed in generally high yield.