Simple synthesis of dimethyl 4-methyl-6-perfluoroalkylisophthalates and dimethyl 5-perfluoroalkylbiphenyl-2,4-dicarboxylates via acyclic precursors

Abstract

Reaction of methyl propynoate 2 with acetylmethylenetriphenylphosphorane 1a or benzoylmethylenetri - phenylphosphorane 1b at 90 °C gives methyl 5-oxo-2-(triphenylphosphoranylidene)hex-3-enoate 4a or methyl 4-benzoyl-2-(triphenylphosphoranylidene)but-3-enoate 4b as the main product, respectively. Phosphoranes 4a or 4b can further react with methyl perfluoroalkynoates 5a and 5b to afford dimethyl 2-(3- oxo-1-perfluoroalkylbut-1-enyl)-4-(triphenylphosphoranylidene)pent-2-enedioates 6a and 6b or dimethyl 2-(2-benzoyl-1-perfluoroalkylvinyl)-4-(triphenylphosphoranylidene)pent-2-enedioates 6c and 6d, respectively. Diemethyl 4-methyl-6-perfluoroalkylisophthalates 7a and 7b or dimethyl 5-perfluoroalkylbiphenyl-2,4-dicarboxylates 7c and 7d were prepared in high yield via intramolecular Wittig reaction of phosphoranes 6a/6b or 6c/6d in benzene or methanol. The structures of compounds 4a, 6a and 7a were confirmed by IR, MS and ¹H, ¹⁹F and ¹³C NMR spectroscopy and elemental analyses. Reaction mechanisms for the formation of compounds 4, 6 and 7 are proposed.