Silver ion-assisted solvolysis of 2,2-dibromo-1-phenylcyclopropanecarboxylic acid: Solvent-dependent competition between decarboxylation and ring closure

The solvolysis of the title compound has been studied in several alcohols ( methanol, 2,2,2-trifluoroethanol, isopropyl alcohol, tert-butyl alcohol and 1,I,1,3,3,3-hexafluoro-2-propanol [HFP]) in the presence of an excess of s liver trifluoroacetate. In all solvents the corresponding butenolide, 4-bro mo-3-phenyl-2(SH)-furanone, was a major or the predominant product. Another product formed in all solvents but HFP was (Z)-4-alkoxy-3-bromo-2-phenyl-2 -butenoic acid, which resulted from solvent attack on intermediate allylic cations. Furthermore, both 3-alkoxy-1-phenyl-1-propyne and 3-alkoxy-1-pheny l-1-propanone were formed except when reactions were performed in HFP; thei r formation involved decarboxylation and their total yield was 15-40%.