First enantioselective addition of diethylzinc and dimethylzinc to prostereogenic ketones catalysed by camphorsulfonamide-titanium alkoxide derivatives

Article abstract of DOI:10.1016/S0040-4020(98)00236-1

The reaction of diethylzinc or dimethylzinc with prostereogenic ketones, in the presence of a stoichiometric amount of titanium tetraisopropoxide and a catalytic amount (20%) of camphorsulfonamide derivatives as chiral ligands leads to the formation of the corresponding enantioenriched tert-alcohols with enantiomeric ratios up to 94.5 : 5.5. the best results were obtained when phenones are used as substrates independently of the dialylzinc reagent. The enantioselectivity shows a linear relationship with the enantiomeric excess of the ligand and seems to be independent of the reaction yield. A tentative catalytic cycle and mechanistic model are proposed for this new reaction.