Platinum-Catalyzed Enantioselective Aldol Addition of Ketene Silyl Acetals to Aldehydes

The first platinum-catalyzed enantioselective aldol reactions are reported. The catalysts are generated from chiral bisphosphine platinum acyl complexes by activation with noncoordinating or weakly coordinating strong acids and can be used to catalyze the enantioselective aldol addition of ketene silyl acetals to various aldehydes. The presence of oxygen and water during catalyst activation is required to obtain enantioselectivity. The enantioselectivities observed in the cases of aliphatic primary aldehydes are more than 90% enantiomer excess. IR and 31 P NMR spectroscopies were used to demonstrate the intermediacy of C-bound platinum enolate in the aldol process.