Abstract

Protonation of the highly reactive 1:1 intermediates, produced in a reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 4-fluorophenol leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce dialkyl 2-(4-fluoro-phenoxy)- 3-(triphenylphosphoranylidene)butanedioates. Dipotassium hydrogen phosphate powder was found to catalyze the conversion of dialkyl 2-(4-fluoro-phenoxy)- 3-(triphenylphosphoranylidene)butanedioates to dialkyl 2-(4-fluoro-phenoxy)-2- butenedioates in solvent-free conditions under microwave (0.5 KW, 3 min) and thermal (90   ◦C, 60 min) conditions