Efficient synthesis of novel 6-Phenylthio-2,4-disubstituted pyrimidines

Abstract

6-Phenylthio-2,4-disubstituted pyrimidines were prepared in five steps starting from barbituric acid. Reaction of barbituric acid with POCl3 in presence of N, N-dimethylaniline furnishes the 2,4,6-trichloropyrimidine, which on reaction with aq. NaOH under reflux yielded the 6-chlorouracil. Reaction of 6-chlorouracil with thiophenol under basic condition furnishes the 6-phenylthiouracil, which on chlorination using excess POCl3 under reflux yielded the key synthon, 6-phenylthio-2,4-dichloropyrimidine. Aromatic nucleophilic substitution reaction of 6-phenylthio-2,4-dichloropyrimidine with a oxygen nucleophile like sodium benzylate and nitrogen nucleophiles like heterocyclic primary amines, aliphatic primary amines and substituted aromatic primary amines furnished the target compounds, 6-phenylthio-2,4-disubstituted pyrimidines respectively in 40-80% yield.