Enantioselective Reduction of N-Arylketimines with S-Chiral Catalysts

Significance

Recently the authors reported on the use of S-chiral sulfinamides in the enantio­selective reduction of ketimines (Org. Lett. 2006, 8, 5913). Based on their observations a variety of second-generation catalysts for this transformation, consisting of two S-chiral sulfinamide groups connected by tethers of different lengths, were designed. With these new catalysts the reduction of different substituted N-arylketimines with trichlorosilane proceeds in good yields and enantio­selectivities. The best catalyst was found to be the simple and highly flexible bissulfinamide 1. The use of several basic additives had only little beneficial effect on the enantioselectivities but lowered the reactivity in most cases. Only the use of 2,6-lutidine (30 mol%) increased the stereoselectivity without decreasing the yield.