Magnesium bromide promoted barbier-type intramolecular cyclization of halo-substituted acetals, ketals, and orthoesters

[摘要] Although acetals, ketals and orthoesters are commonly used as protective groups against organometallic reagents, Grignard reagents derived from halo-acetals, ketals, or orthoesters cyclize intramolecularly under MgBr2 promoted conditions, giving rise to the corresponding cycloalkanol and cycloalkanone derivatives. Our results also suggest a Lewis acid catalyzed push-pull mechanism operating for the cyclization. (C) 1999 Elsevier Science Ltd. All rights reserved.

[发布日期] 1999-12-03