Rhenium-Catalyzed Regio- and Stereoselective Addition of Imines to Terminal Alkynes Leading to <i>N</i>-Alkylideneallylamines

The reaction of terminal alkynes with imines using ReBr(CO)(5) as a catalyst results in the production of N-alkylideneallylamines and not the conventional propargylamines. The substituent on the imine nitrogen is important, and a diphenylmethyl group gave the best result. The catalytic cycle of this regioselective C-C bond forming reaction appears to involve the formation of an alkynyl rhenium species and subsequent nucleophilic attack of the alkynyl β-carbon atom on the imine carbon to give a vinylidene rhenium species.