A facile synthesis of dimethyl 4-(alpha-furyl)- and 4-(alpha-thienyl)-6-perfluoroalkylisophthalates via acyclic precursors

In the presence of K2CO3, reaction of methyl propynoate 2 with (alpha-furoyl)methyltriphenylphosphorium bromide la or (alpha-thienacyl)methyltriphenylphosphonium bromide Ib gave methyl 4-(alpha-furoyl)-2-(triphenylphosphoranylidene)but-3-enoate 4a or methyl 4-(alpha-thienacyl)-2-(triphenylphosphoranylidene)but-3-enoate 4b as the major product. Phosphorane 4a or 4b could react further with methyl perfluoroalkynoates 5a-b to afford dimethyl 2-(alpha-furoyl-1-perfluoroalkylvinyl)-4-(triphenylphosphoranylidene)pent-2-enedioates 7a-b or dimethyl 2-(alpha-thienacyl-1-perfluoroalkylvinyl)-4-(triphenylphosphoranylidene)pent-2-enedioates 7c-d, respectively. Dimethyl 4-(alpha-furyl)-6-perfluoroalkylisophthalates 8a-b or dimethyl 4-(alpha-thienyl) -6-perfluoroalkylisophthalates 8c-d were prepared in high yields via intramolecular Wittig reaction of phosphoranes 7a-d under heating in a sealed tube in xylenes. The structures of these compounds were confirmed by IR spectroscopy, mass spectrometry, H-1, F-19 and C-13 NMR spectra, and elemental analyses. Reaction mechanisms of the formation of compounds 4, 6, 7 and 8 were also proposed. (C) Elsevier Science S.A.