作者:T. Jon Seiders、D. William Ward、Robert H. Grubbs
DOI:10.1021/ol0165692
日期:2001.10.1
[reaction: see text] The first enantioselective ruthenium olefinmetathesis catalysts have been prepared, and high enantiomeric excesses (up to 90%) are observed in the desymmetrization of achiral trienes. A model consistent with the stereochemical outcome of the reactions is described and suggests side-on olefin binding and reorganization of the halide ligands.
Chiral relay in NHC-mediated asymmetric β-lactam synthesis I; substituent effects in NHCs derived from (1R,2R)-cyclohexane-1,2-diamine
作者:Nicolas Duguet、Adele Donaldson、Stuart M. Leckie、James Douglas、Peter Shapland、Thomas B. Brown、Gwydion Churchill、Alexandra M.Z. Slawin、Andrew D. Smith
DOI:10.1016/j.tetasy.2010.03.001
日期:2010.3
The synthesis of a range of C-2-symmetric imidazolinium salts from (1R,2R)-cyclohexane-1,2-diamine, and an evaluation of the reactivity and asymmetric induction of the derived NHCs as catalysts for the asymmetric synthesis of beta-lactams, is reported. In this series, optimal enantioselectivity (up to 70% ee) is observed using N-benzyl or N-1-naphthylmethyl-substituted NHCs, consistent with a chiral relay effect operating to dictate the stereochemical outcome of this reaction. (C) 2010 Elsevier Ltd. All rights reserved.