Controlled Ring-Opening of Siloxy­difluoro­cyclo­propanes for Carbocyclization: Synthesis of Difluoro­cyclo­pentenones

A highly controlled ring opening of siloxy­difluoro­cyclo­propanes, formed by nBuN4Br-catalyzed difluorocyclo­propanation of methyl vinyl ketones bearing a β-alkylthio group by using TMSCF2Br as a unique difluorocarbene source, results in metal difluoro­homoenolates with assistance of copper or silver followed by an intramolecular addition and elimination reaction leading to α-gem-difluorocyclopentenones efficiently.