Heck-type 5-endo-trig cyclizations promoted by vinylic fluorines: Ring-fluorinated indene and 3H-pyrrole syntheses from 1,1-difluoro-1-alkenes

Arylpalladium or aminopalladium species bearing a 2,2-difluorovinyl group undergo an unusual 5-endo alkene insertion followed by β-fluorine elimination. These processes provide a facile access to ring-fluorinated five-membered carbocyclic and heterocyclic compounds starting from an o-(3,3-difluoroallyl)phenyl trifluoromethanesulfonate and 3,3-difluoroallyl ketone O-pentafluorobenzoyloximes. In both systems, the two vinylic fluorine atoms are essential for Heck-type 5-endo-trig cyclizations.