Enantioselective Synthesis of α‑Silylamines by Meerwein–Ponndorf–Verley-Type Reduction of α‑Silylimines by a Chiral Lithium Amide

Meerwein–Ponndorf–Verley-type reduction of N-tosylsilylimines with chiral lithium amide 2 affords α-silylamines in high enantioselectivity. Since the enantioselectivity observed was inconsistent with our previously proposed chairlike six-membered transition structure, we performed density functional theory (DFT) calculations on transition states leading to (S)- and (R)-7a and (S)- and (R)-7e using an N-phenylsulfonyl derivatives 12 and 13 as model systems. Results of the calculations showed that the structures are considerably deformed from the chairlike form with steric repulsions between the 1′-methylene group and the imine-carbon substituents playing an important role in the control of the enantioselectivity.