Reactions of mesomeric fluorocarbanions with acid anhydrides. Transformation of trifluoromethyl groups into fluorocarbonyl and perfluoroacyl groups

Abstract It was found that the reaction of mesomeric fluorocarbanions of the CF 3 C θ XCOY type with benzoic anhydride leads to the loss of benzoyl fluoride and the formation of mesomeric carbanions of the FCO C θ XCOY type. In a similar reaction with perfluorocarboxylic acid anhydrides, besides a CF 3 →COF transformation, further change of COF into COR F is observed, leading to the formation of salts containing mesomeric anions of the R F CO C θ XCOY type, which, upon acidification, give 1,1- -bis(perfluoroacyl)-2,2,2-trifluoroethanes CF 3 CH(COR F ) 2 , tris- (perfluoroacyl)methanes (R F CO) 3 CH and bis(trifluoroacetyl)- acetic ester (CF 3 CO) 2 CHCOOMe. It has been shown that perfluoroalkyl groups in β-diketones and β,β′-triketones may hinder enolization despite their electron-attracting effect.