An efficient dehyrohalogenation method for the synthesis of α,β,β-trifluorostyrenes, α-chloro-β,β-difluorostyrenes and E-1-arylperfluoroalkenes

Dehydrofluorination of 1-aryl-1,2,2,2-tetrafluoroethanes (ArCHFCF3) and 1-aryl-1-chloro-2,2,2-trifluoroethane (ArCHClCF3) using lithiumhexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) at room temperature produced 1,2,2-trifluorostyrene and 1-chloro-2,2-difluorostyrene, respectively, in very good isolated yields. Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhCHFCF2CF3) and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (PhCHFCF2CF2CF3) using LHMDS produced the corresponding substituted olefins (1-phenyl-1,2,3,3,3-pentafluoroprop-1-ene and 1-phenyl-1,2,3,3,4,4,4-pentafluorobut-1-ene) in good yield and high E-selectivity. Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane (PhCHClCF2CF3) and 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluorobutane (PhCHClCF2CF2CF3) produced a mixture of the corresponding E and Z olefins (PhCClCFCF3 and PhCClCFCF2CF3) in good yield.