Enantioselective reductive coupling of acetylene to N-arylsulfonyl imines via rhodium catalyzed C-C bond-forming hydrogenation:: (Z)-Dienyl allylic amines

The first highly enantioselective catalytic vinylation of aldimines to furnish allylic amines is reported. Exposure of aromatic and aliphatic N-arylsulfonyl aldimines 1a-12a to equal volumes of acetylene and hydrogen gas at 45 degrees C and ambient pressure in the presence of chirally modified cationic rhodium catalysts provides the (Z)-dienyl allylic amines 1b-12b in highly optically enriched form (93-98% ee) and as single geometrical isomers (>95:5, Z/E). The coupling products 1b-12b arise via multicomponent coupling of four molecules: two molecules of acetylene, a molecule of aldimine, and elemental hydrogen. Unlike other imine additions involving nonstabilized carbanions, the present protocol circumvents use of preformed organometallic reagents.