Iridium-catalyzed asymmetric hydrogenation of unfunctionalized enamines.

Optically active tertiary amines are readily prepared by iridium-catalyzed asymmetric hydrogenation of unfunctionalized enamines (see scheme). The best enantioselectivities with >90% ee were obtained with N-aryl- and N-benzyl-substituted enamines with a terminal double bond. The hydrogenation of enamines derived from cyclic ketones, which has not been reported yet with other catalysts, gave enantiomeric excesses of up to 87%.