On the Way to Chiral Copper(I) Arenethiolate Catalysts for the Enanatioselective Conjugate Addition of Methyl Lithium and Methyl Magnesium Iodide to Benzylideneacetone

Abstract

Selective conjugate addition (0 % enantiomeric excess (e.e.)) of organoarenethiolatocuprates (from methyl lithium and 2-[1-(R)-(dimethylamino)ethyl]phenylthiolatocopper(I), CuSAr*) to benzylideneacetone (BA) is found up to a LiMe/CuSAr* ratio of 21 indicating the potential of the chiral SAr*-anion as non-transferable group; at higher ratios only 1, 2-addition occurs. Reactions of methyl magnesium iodide with BA in the presence of a catalytic amount of CuSAr* (9 mol%) result in exclusive conjugate addition with 57% e.e..