view:20506 Last Update: 2019-1-30
Ali Souldozi; Ali Ramazani; Nader Noshiranzadeh|
Dipotassium Hydrogen Phosphate Powder Catalyzed Conversion of Dialkyl 2-(2,5-Dihydroxyphenyl)-3-(1,1,1-triphenyl-5-phosphanylidene)succinates to Alkyl 6-Hydroxy-2-oxo-2H-chromen-4-carboxylates
Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by hydroquinone leads to vinyltriphenylphosphonium salts, which undergo an electrophilic substitution reaction with a conjugate base to produce corresponding stabilized phosphorus ylides. Dipotassium hydrogen phosphate powder was found to catalyze conversion of the stabilized phosphorus ylides to alkyl 6-hydroxy-2-oxo-2H-chromene-4- carboxylates under thermal or microwave irradiation in solvent-free conditions.