Reaction of perfluorinated and partially fluorinated olefins with fluorinated thioketones. Efficient synthesis of perfluorinated 1,3-dithioles

Abstract While the reaction of F-butene-2 and F-pentene-2 with sulfur, CsF catalyst and 2,2,4,4-tetrakis(trifluoromethyl)-dithietane-1,3 at ambient temperature produced an equimolar mixture of the corresponding perfluorinated 1,3-dithiole and branched perfluorinated polysulfides, it was discovered that the formation of undesirable polysulfides can be avoided by employment of monohydrofluorolefins in this process. The reaction of RfCF=CHRf, sulfur, 2,2,4,4-tetrakis(trifluoromethyl)-dithietane-1,3 and an excess of CsF (or KF) resulted in selective formation of previously unknown perfluorinated 2,2-bis(trifluoromethyl)-1,3-dithioles in 47–74 % yield. Surprisingly, even 2,3-H-hexafluorobutene-2 was active in this reaction resulting in selective formation of the corresponding 2,2,4,5-(tetrakis)trifluoromethyldithiole-1,3.