Synthesis of Difluorinated Enynes through Sonogashira-Type Coupling

The Sonogashira-type coupling of 2,2-difluoroethenyl tosylate with a variety of aliphatic and aromatic terminal alkynes proceeds smoothly even at room temperature to produce the corresponding difluorinated enyne derivatives. 2,2-Difluoroethenyl tosylate is a useful difluoroethenyl source because of its ready availability from 2,2,2-trifluoroethanol. Some of the obtained enynes exhibit strong fluorescence in the solid state. Further derivatization of a difluorinated enyne through Rh(III)-catalyzed oxidative coupling has also been examined.