Enantioselective Synthesis of α-Silylamines by Meerwein–Ponndorf–Verley-Type Reduction of α-Silylimines by a Chiral Lithium Amide
摘要:
Meerwein-Ponndorf-Verley-type reduction of N-tosylsilylimines with chiral lithium amide 2 affords alpha-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.
Meerwein-Ponndorf-Verley-type reduction of N-tosylsilylimines with chiral lithium amide 2 affords alpha-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.
[3 + 2] Annulation of β-Heteroatom-Substituted α,β-Unsaturated Acylsilanes with Methyl Ketone Enolates: Scope and Investigation of the Reaction Course
作者:Kei Takeda、Kenji Yamawaki、Noriaki Hatakeyama
DOI:10.1021/jo0160219
日期:2002.3.1
A new route to (Z)-beta-silylacryloylsilanes 10 and the improved conditions for the [3 + 2] annulation using 10 and alkyl methyl ketone enolates are reported. Also, details of investigations defining a reactioncourse of the [3 + 2] annulation using beta-phenylthio- and beta-trimethylsilyl-acryloylsilanes 1 (X = SPh, SiMe(3)) and alkyl methyl ketone enolates are described.