Facile Synthesis and Ring‐Opening Cross Metathesis of Carbo‐ and Heterocyclic Bicyclo[3.2.1]oct‐6‐en‐3‐ones Using Gaseous Olefinic Reaction Partners

Abstract

Abstract The title compounds were prepared by a facile [4+3]‐cycloaddition strategy involving sonochemistry. The oxyallyl species required for the reaction with the corresponding diene was generated from a suitable perbromo ketone with activated zinc under sonification conditions. The resulting dibromo bicyclo compounds were reduced to the target products using a Cu/Zn couple. Ring‐opening cross metathesis of the resulting bicyclic species was established as an efficient method for the diastereoselective preparation of cis ‐3,5‐disubstituted cycloketones. Especially gaseous olefins gave symmetrical and unsymmetrical products as versatile platforms for subsequent transformations. This is the first example of such a ring‐opening reaction of a non‐strained ring system.