Synthesis of bis(enolnonaflates) and their 4-exo-trig-cyclizations by intramolecular Heck reactions

Starting from dimedone, novel 1,3-bis(enolnonaflates) (nonafluorobutanesulfonates) have been prepared in four efficient steps. Cyclization of these 1,5-hexadienes under Palladium catalysis proceeded cleanly to give bicyclo[4.2.0]octadienes and bicyclo[4.2.0]octenones, respectively, by an unprecedented 4-exo-trig process. Insertion in one enolsulfonate moiety, intramolecular cyclization and subsequent second insertion after intermolecular reaction with alkenes (acrylates) or alkynes (3,3-dimethylbutyne) led to novel, highly congested hydrocarbons. Application of a chiral catalyst system resulted in modest asymmetric induction to furnish an enantioselective Heck-type desymmetrization reaction product.