Asymmetric Synthesis of 1,3-Diamines. II: Diastereoselective Reduction of Atropisomeric N-tert-Butanesulfinylketimines

Chiral, nonracemic o-aminobenzylamines were prepared in a highly diastereoselective reduction of atropisomeric N-tert-butanesulfinylketimines. The ortho-substituent ensures the distinct reactivity of atropisomers 4d−f. The free energy of activation for atropisomerization of sulfinylimines 4d−f in THF-d₈ was determined by NMR methods to range from 70.8 to 97.9 kJ/mol.