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

Abstract

Ozonolysis of mono-substituted alkenes A- 1 followed by reacting with a preheated mixture of CH 2Br 2–Et 2NH affords α-substituted acroleins A- 2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A- 2 can be easily converted to α-methylene esters A- 4 , which could be further converted to the corresponding α-keto esters A- 5 . This methodology can be also applied to the preparation of α-methylene lactones B- 4 , α-methylene lactams, and α-keto lactones B- 5 with various ring sizes.