Asymmetric Synthesis of 1,3-Diamines by Diastereoselective Reduction of Enantiopure <i>N</i>-<i>tert</i>-Butanesulfinylketimines: Unusual Directing Effects of the <i>ortho</i>-Substituent

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