Rhenium(I)-catalyzed reaction of terminal alkynes with imines leading to allylamine derivatives

The rhenium-catalyzed reaction of terminal alkynes with imines gives N-alkylideneallylamine derivatives. A diphenylmethyl group as the substituent on the imine nitrogen gave the best result. Deuterium labeling experiments revealed that the regioselective addition of both the hydrogen and the N-alkylideneaminoalkyl group to the terminal alkynes also proceeded stereoselectively. While alkynes bearing primary and secondary alkyl-, vinyl-, and aryl groups were applicable to the catalytic reaction, tertiary alkyl-and silyl-substituted alkynes gave propargylamines. The C-C bond-forming step via the nucleophilic attack of the alkynyl beta-carbon on the imine carbon leading to the formation of a vinylidene rhenium species appears to be involved in the catalytic cycle.