Ring-opening of epoxides 1 by heteroatom-substituted allyl anions 2 occurs with high regioselectivity. In situ tosylation of the resulting alkoxides 3 or tosylation of the corresponding alcohols 4 yields 4-pentenyl tosylates 5. Anion generation by deprotonation or desilylation gives vinylcyclopropanes 9 by an S(Ni) process. The approach allows annulation of vinylcyclopropanes onto existing five- and six-membered rings and synthesis of vinylcyclopropanes with functionality on the olefin.
Lewis acid supported reactions of 1,3-bis(silyl)allyl compounds with epoxides — inter- and intramolecular versions
作者:Anette Nowak、Oliver Bolte、Ernst Schaumann
DOI:10.1016/s0040-4039(97)10675-x
日期:1998.2
Easily available 1,3-bis(silyl)allyl compounds react with epoxides under Lewis acid catalysis to give interesting synthetic building blocks. The course of reaction depends on the stabilization of cationic intermediates by the silicon beta-effect. (C) 1998 Elsevier Science Ltd. All rights reserved.