[4 + 2]-Annulation of MBH-Acetates of Acetylenic Aldehydes with Imidazoles/Benzimidazoles To Access Imidazo[1,2-a]pyridines/Benzimidazo[1,2-a]pyridines.

An unprecedented one-pot successive base-mediated allylic amination/cycloisomerization reaction strategy has been developed to construct diversely substituted imidazo[1,2-a]pyridines and benzimidazo[1,2-a]pyridines in good to excellent yield. The advantage of this unique [4 + 2]-annulation lies in the employment of readily accessible starting materials, Morita-Baylis-Hillman acetates of acetylenic aldehydes as C4 synthons, and simple imidazoles or benzimidazoles as C2 synthons.