Rhodium-catalyzed asymmetric addition of terminal alkynes to diarylphosphinylallenes.

The presence of an acid was found to be essential in the rhodium-catalyzed asymmetric addition of terminal alkynes to diarylphosphinylallenes giving exo-enynes in high yields with high regio- and enantioselectivity. The stereochemical outcome is determined at the protonolysis of the pi-allylrhodium(I) intermediate involved in the catalytic cycle.