Synthesis of Indolizines via Reaction of 2-Substitued Azaarenes with Enals by an Amine-NHC Relay Catalysis.

A metal-free catalytic strategy for the facile synthesis of biologically relevant molecular architectures indolizines and imidazopyridines has been developed. The process is promoted by amine and N-heterocyclic carbene (NHC) relay catalysis via Michael addition-[3 + 2] fusion of simple azaarenes and α,β-unsaturated aldehydes. The preparative power is demonstrated in the synthesis of anxiolytic drug saripidem via two simple one-pot operations with overall 45% yield.