Transition-metal-free synthesis of indolizines via [3 + 2]-annulation from α-bromoenals and 2-substituted azaarenes

A transition-metal-free synthetic approach to synthesize indolizines from α-bromo-substituted enals and simple 2-substituted azaarenes has been developed. A variety of functional groups were tolerated under mild reaction conditions. Moreover, Michael addition, intramolecular N-alkylation and aromatization were involved in this convergent and feasible "one-pot" tandem reaction to afford the annulation products in moderate to good yields.