Platform for Ring-Fluorinated Benzoheterole Derivatives: Palladium-Catalyzed Regioselective 1,1-Difluoroallylation and Heck Cyclization

The synthesis of difluoromethylene-containing heterocycles was achieved via the palladium-catalyzed 1,1-difluoroallylation of heteronucleophiles followed by intramolecular Heck reaction. The allylic substitution of 3-bromo-3,3-difluoropropene was regioselectively accomplished by heteronucleophiles without rearrangement to give the corresponding 1,1-difluoroallylated compounds whose Heck cyclization proceeded in a 5-exo manner to afford ring-difluorinated indolines and dihydrobenzofurans. Their defluorinative allylic substitution further provided 2-fluoroindoles and 2-fluorobenzofurans.