3-Polyfluoroacylmethylenephthalides: Synthesis and Structure

Abstract

3-Polyfluoroacylmethylenephthalides (R^F = CF₃, CF₂CF₂H, C₂F₅) can be synthesized conveniently by cyclodehydration of 1-(2-carboxyphenyl)-3-polyfluoroalkylpropane-1,3-diones, obtained from o-acetylbenzoic acid and polyfluorinated esters, as a separable mixture of Z- and E-isomers. In solution, the Z- and E-isomers of 3-polyfluoroacylmethylenephthalides are interconvertable. For CD₃CN and (CD₃)₂SO solutions of 1-(2-carboxyphenyl)-3-polyfluoroalkylpropane-1,3-diones a ring–chain tautomerism is observed. The structures of the new compounds have been determined by heteronuclear nuclear magnetic resonance (NMR) spectroscopy and nuclear Overhauser effect (NOE) experiments.