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.

采用手性锂酰胺（chiral lithium amide）2对N-对甲苯磺酰基硅亚胺（N-tosylsilylimines）进行Meerwein-Ponndorf-Verley型还原反应，可高对映选择性地合成α-硅基胺（α-silylamines）。鉴于观测到的对映选择性与我们此前提出的椅式六元环过渡结构不符，我们以N-苯磺酰基衍生物12和13作为模型体系，对生成(S)-、(R)-7a以及(S)-、(R)-7e的过渡态开展了密度泛函理论（DFT）计算。计算结果表明，该过渡态结构与椅式构型存在显著畸变，其中1′-亚甲基与亚胺碳取代基之间的空间排斥作用对对映选择性的调控发挥了关键作用。