Synthesis of 3-substituted 8,9-didehydroazepino[4,5-b]indolines via ring expansion reaction of pyrroloindolines

An unexpected ring expansion reaction was observed to give the 3-substituted 8,9-didehydroazepinoindolines when 3-substituted pyrroloindolines reacted with electron-deficient acetylenes in the presence of catalytic amount of CuI. The ring expansion reaction proceeded via a three-step one-pot cascade pathway of aza-Michael-addition/ring-opening/iminium-cyclization.