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 towards hydroamination.