Regioselective ortho-hydrodefluorination of pentafluorobenzoic acid by low-valent nickel complexes

2,3,4,5-Tetrafluorobenzoic and 3,4,5-trifluorobenzoic acids were prepared in high yields by reaction of C6F5COOH with zinc in the presence of NiCl2–2′-bipyridine (or 1,10-phenanthroline) complexes.