Rhodium-catalyzed conjugate addition of aryl- and alkenyl-stannanes to α,β-unsaturated carbonyl compounds

The addition of aryl- or alkenyl-trimethylstannanes to α,β-unsaturated carbonyl compounds in the presence of a catalytic amount of a cationic rhodium complex ([Rh(cod)(MeCN)2]BF4) and water to afford the conjugate addition products in good yields was examined. It was observed that addition of water was necessary for the reaction to proceed smoothly. The aryl- or alkenyl-rhodium complex, which is generated by the transmetalation from the organotin compound, is considered to be the active catalytic species.