Sodium trifluoroacetate: an efficient difluorocarbene precursor for alkenes

A novel and efficient difluorocarbene precursor was achieved. In a convenient procedure, a variety of alkenes could be gem-difluorocyclopropanated with sodium trifluoroacetate to give the corresponding products in moderate to high yields, using azobisisobutyronitrile (AIBN) as the catalyst.