Potassium Iodide → Phenytoin Impurity 31

Participants

Reaction Conditions

Reaction Steps

A mixture of 250 kg 3-(chloromethyl)-5,5-diphenyl-2,4-imidazolidinedione from Step (A), 270 kg of potassium dibenzyl phosphate, 6 kg of potassium carbonate, 0.75 kg of potassium iodide, and 500 kg of acetonitrile is heated at 70° C. to reflux for 2 to 5 hours or until the reaction is essentially complete. The reaction mixture is cooled to 40° C. to 65° C. and filtered. The solution is stirred with at least 11 kg of activated carbon and filtered using a filter-aid. The reaction solvent is replaced by adding toluene in portions and vacuum distilling. The resulting slurry is cooled to less than 5° C. The title compound is collected by filtration and washed with cold toluene. The wet cake is dried at 50° C. under vacuum to give phosphoric acid dibenzyl ester 2,5-dioxo-4,4-diphenyl-imidazolidin-1-ylmethyl ester, 315 kg (70% yield); mp 118.6-119.7° C.

Provenance & Evidence