Chemistry of aminophenols. Part 1: Remarkable additive effect on Sonogashira cross-coupling of 2-carboxamidoaryl triflates and application to novel synthesis of indoles

A novel and general synthesis of indoles has been established by utilizing 2-aminophenols as the starting materials. The key step is a modified Pd(0)–Cu(I)-catalyzed cross-coupling of 1-alkynes with 2-carboxamidoaryl triflates in the presence of n-Bu4NI as the additive. The 2-alkynylanilides obtained were subjected to an alkoxide-mediated cyclization to provide a number of indole containing compounds possessing substituents at the C2, C4, C5, and/or C6 position(s) in good overall yields.