Abstract The insitu reaction of triphenylphosphine, tribromofluoromethane, and a difluoromethylene olefin successfully allows the capture of the intermediate dibromofluoromethide ion. With fluorinated propenes, the product is an allylic dibromofluoromethyl alkene; with longer chain fluoro-olefins the major product is a 1-bromo- 1, 3-fluorinated diene derivative. Pentafluoropyridine yields 4- ...