Asymmetric Diels-Alder reactions employing modified camphor-derived oxazolidin-2-one chiral auxiliaries
作者:Malcolm R. Banks、Alexander J. Blake、J.I.G. Cadogan、Allan A. Doyle、Ian Gosney、Philip K.G. Hodgson、Paul Thorburn
DOI:10.1016/s0040-4020(96)00070-1
日期:1996.3
Transposition of the dormant methyl group from C-1 in chiral oxazolidin-2-one 2 to C-7 in a six step synthetic sequence from (1R)-camphor 5 creates a novel transfigomer 4 with sufficient pi-topological bias to induce excellent levels of asymmetric induction in Lewis-acid catalysed Diels-Alder reactions of its alpha,beta-unsaturated carboximide derivatives with cyclopentadiene. Further modification of 4 by replacement of the C-7 methyl group with an ethyl substituent raises the level of diastereoselectivity for the acrylate derivative 11a from 81 to >95% d.e..