Fluorinated phosphonium ylides: versatile in situ Wittig intermediates in the synthesis of hydrofluorocarbons

Abstract

A simple and convenient technique has been developed for the synthesis, characterisation and isolation of hydrofluoro/hydrohalofluorocarbons such as chlorodifluoromethane (CF 2ClH), difluoromethane (CF 2H 2), bromodifluoromethane (CF 2BrH) and dibromofluoromethane (CFBr 2H) as possible chlorofluorocarbon (CFC) alternatives. The Wittig reaction of carbonyl compounds with in situ generated triphenylphosphonium ylides in DMF forms terminal fluoroolefins. However, in the absence of the carbonyl moiety these ylides undergo decomposition. The high reactivity of fluoromethylene triphenylphosphonium ylides in DMF in the absence of the carbonyl moiety has been exploited for the first time to design the synthesis of hydrofluorocarbons.