Diastereoselective Synthesis of Bicyclo[3.3.0]octenones by Copper-Catalyzed Transannular Ring-Closing Reaction.

A novel and efficient copper-catalyzed transannular ring-closing reaction of eight-membered rings has been developed that provides a straightforward way to synthesize bicyclo[3.3.0]octane derivatives in good yields. Mechanistic studies revealed that the reaction pathway might involve chlorination followed by the Kornblum reaction. Readily accessible starting materials and good functional group tolerance make this procedure attractive.