Asymmetric synthesis of 1,3-diamines by diastereoselective reduction of enantiopure N-tert-butanesulfinylketimines: unusual directing effects of the ortho-substituent.

Chiral, nonracemic 1,3-diamines were prepared in a highly diastereoselective reduction of diaryl N-tert-butanesulfinylketimines. Correlation between facial selectivity of the reduction and E or Z geometry of the starting ketimines suggests involvement of a cyclic transition state for the reduction. The ortho-substituent controls the geometry of N-tert-butanesulfinylketimines in the solid state and provides additional stabilization of the cyclic transition state.