Dibromomethane as one-carbon source in organic synthesis: a versatile methodology to prepare the cyclic and acyclic alpha-methylene or alpha-keto acid derivatives from the corresponding terminal alkenes

摘要

Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords alpha-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these alpha-substituted acroleins A-2 can be easily converted to alpha-methylene esters A-4, which could be further converted to the corresponding alpha-keto esters A-5. This methodology can be also applied to the preparation of alpha-methylene lactones B-4, alpha-methylene lactams, and alpha-keto lactones B-5 with various ring sizes. (C) 2004 Elsevier Ltd. All rights reserved.