Water-tolerant enantioselective carbonyl-ene reactions with palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP

Palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP have been proved to be water-tolerant in enantioselective carbonyl-ene reactions, thus arylglyoxal monohydrate could be used directly as substrate achieving good to excellent enantioselectivities as high as 95.4% e.e.. The enantioselective carbonyl-ene reactions using phenylglyoxal monohydrate as substrate with four alkenes including methylenecyclohexane, 2,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene and alpha-methylstyrene, were investigated demonstrating comparable oreven higheryields and enantioselectivities in comparison with the corresponding carbonyl-ene reactions using dry phenylglyoxal as substrate for both palladium(II)BINAP catalyst and platinum(II)-BINAP catalyst. The palladium(II) and platinum(II)-BINAP catalyzed enantioselective carbonyl-ene reactions between 4-methylphenylglyoxal monohydrate and the four alkenes were also investigated affording enantioselectivities between 76.2% and 91.8% e.e.. A mechanism involving the coordination of arylglyoxal and 2,2-dihydroxy-1-phenylethanone with chiral catalyst was proposed to interpret the enantioselective carbonyl-ene reactions using arylglyoxal monohydrate as substrate. (c) 2006 Elsevier B.V. All rights reserved.