Regiospecific preparation of α,α-dihalofluoromethyl perfluoroalkyl ketones via halogenation of perfluoro betaines
摘要:
Acylation of fluorinated phosphoranium salts with perfluorinated acyl chlorides provided the corresponding (Z)-perfluoro betaines in high yield. Subsequent chlorination or bromination of the betaines regiospecifically yields the alpha,alpha-dihalofluoromethyl perfluoroalkyl ketones. Halogen specificity is best controlled via use of CFCl3/Cl2 for the preparation of dichloroketones and CFBr3/Br2 for the corresponding dibromoketones. The dihalophosphorane by-product can promote a halogen-exchange reaction with ketones.