PREPARATION OF ALPHA,ALPHA-DIBROMOCYCLOBUTANONES FROM OLEFINS - A SIMPLE PROCEDURE FOR THE REGIOSELECTIVE FUNCTIONALIZATION OF OLEFINS

摘要

Dibromoketene is prepared by in-situ Zn dehalogenation of tribromoacetyl bromide in the presence of POCl3. Under these conditions, the cycloaddition of dibromoketene with olefins 5 yields alpha,alpha-dibromocyclobutanones 2, which are cleaved with alkoxides to yield beta-dibromomethyl esters 4. Several examples are given. For monosubstituted olefins, the functionalization is regioselective, the methoxycarbonyl group being introduced at the terminal C-atom. [References: 20]