Cyclization of 4-(2-aminoanilino)-2-benzylthiopyrimidine to novel 1-(2-benzylthiopyrimidin-4-yi)-2-substituted benzimidazoles

Abstract

1-(2-Benzylthiopyrimiden-4-yl)-2-substituted benzimidazoles 6a-d were prepared efficiently in four steps. Reaction of 2-thiouracil with benzyl chloride in presence of base, furnishes 2-benzylthiouracil 2. This on chlorination with excess POCl3 furnishes 4-chloro-2- benzylthiopyrimidine 3. Compound 3 on reaction with ortho-phenylenediamine via aromatic nucleophilic displacement reaction yielded 4-(2-aminoanilino)-2- benzylthiopyrimidine 4. This on cyclization with CS2 in presence of base furnishes 1-(2-benzylthiopyrimidin-4-yl)-2-thiobenzimidazole 5. Compound 5 on reaction with alkyl, aryl halides and hydrazine hydrate yielded target compounds 6a-d in 52-62% yield.