Base-catalyzed stereoselective intermolecular addition of imidazoles onto alkynes: an easy access to imidazolyl enamines

An efficient transition-metal free approach for the regio- and stereoselective addition of imidazoles 1a-f onto alkynes 2a-l to provide the Z- and E isomers of imidazolyl enamines 3a-q and 4a-d using catalytic amount of KOH is described. Stereoselectivity of the addition products (Z and E isomer) was found to be dependent upon time. Competitive experiments show that imidazole is less reactive than pyrrole and more reactive than aniline toward hydroamination.