Chromium-Catalyzed Allylic Defluorinative Ketyl Olefin Coupling

Herein we report a chromium-catalyzed allylic defluorinative ketyl olefin coupling between aldehydes and α-trifluoromethyl alkenes, which provides novel and efficient access to diverse gem-difluorohomoallylic alcohols. Remarkably, the high chemoselectivity of this reaction enables the conversion of the formyl moiety in the presence of various easily reducible functionalities including ketone, organohalides, aziridine, sulfone, alkyne, and unactivated alkene. The utility of this method is demonstrated by various simple derivatizations of the attached hydroxyl group of the coupling products. The preliminary mechanistic investigations suggest a reaction pathway with a rate-limiting C-C forming step followed by facile β-fluoro elimination.