Cu-catalyzed cascade difluoroalkylation/5-endo cyclization/β-fluorine cleavage of ynones.

A copper-catalyzed, redox-neutral cascade difluoroalkylation/5-endo annulation/β-fluorine cleavage of ynones is developed, providing a direct and stereoselective method to access synthetically important α-monofluoroalkenyl cyclopentanones. Mechanistic studies suggest an unprecedented Cu^II-assisted β-fluorine fragmentation, which may be valuable for the challenging but important C–F bond activation. Moreover, the in situ generated difluorocarbene was found to serve as an effective reductant for the regeneration of copper(I) catalyst, thus avoiding the addition of external reductants. [ABSTRACT FROM AUTHOR]