Studies on the Bisoxazoline- and (−)-Sparteine-Mediated Enantioselective Addition of Organolithium Reagents to Imines
作者:Scott E. Denmark、Noriyuki Nakajima、Cory M. Stiff、Olivier J.-C. Nicaise、Michael Kranz
DOI:10.1002/adsc.200800017
日期:2008.5.5
The enantioselective addition of organolithiumreagents to N-anisyl aldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 95.5:4.5 er)
Asymmetric Reduction of Imines with Trichlorosilane, Catalyzed by Sigamide, an Amino Acid-Derived Formamide: Scope and Limitations<sup>†</sup>
作者:Andrei V. Malkov、Kvetoslava Vranková、Sigitas Stončius、Pavel Kočovský
DOI:10.1021/jo900561h
日期:2009.8.21
nonaromatic ketones 1−5, in which the steric difference between the alkyl groups R1 and R2 is sufficient. Simple nitrogen heteroaromatics (8a,b,d) exhibit low enantioselectivities due to the competing coordination of the reagent but increased steric hindrance in the vicinity of the nitrogen (8c,e) results in a considerable improvement. Cyclic imines 32d-d exhibited low to modest enantioselectivities.