Reduction of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-3H-1,2-dithiole-3-thione with sodium sulfide: Synthesis of fluoro-containing sulfur-rich heterocycles

Treatment of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-3H-1,2-dithiole-3-thione with 2 equivalents of sodium sulfide gives after acidification 3,4-difluoro-2-mercapto-1,6,6aλ4-trithiapentalene, which can be further reduced by sodium sulfide to 3,5-difluoro-4-mercapto-thiopyran-2-thione.