AbstractThe title compounds 5a–‐5c were prepared via the reaction of methyl 2‐perfluoroalkynoates (4) with methyl 5‐oxo‐4‐(triphenylphosphoranylidene)hex‐2‐enoate (3), which was obtained from the reaction of methyl propynate (2) with acetylmethylenetriphenylphosphorane (1) at–‐5–0°C. Intramolecular elimination of Ph3PO took place when compound 5 was heated in aqueous methanol at 115–120°C in sealed tube, yielding dimethyl 2‐trifluoromethyl‐4‐methylisophthalate (6a) from 5a and methyl 5‐acetyl‐4‐hydroxy‐2‐heptafluoropropanylbenzoate (6b) from 5b, respectively. The structures of compounds5, 6a and 6b were confirmed by IR, MS,1H NMR,19F NMR and13C NMR spectroscopy and elemental analyses. Reaction mechanisms for the formati