Selective cyclization of S‐substituted pyrimidinethione: Synthesis and antimicrobial evaluation of novel polysubstituted thiazolopyrimidine and thiazolodipyrimidine derivatives

Abstract

AbstractThe synthetic strategy is based on alkylation of 4‐aryl‐N‐(4‐chlorophenyl)‐6‐methyl‐2‐thioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxamide derivatives IV a–g, with some alkyl halides and α‐haloketones, namely, methyl iodide, chloroacetonitrile, and phenacyl bromide to give the corresponding S‐substituted derivatives Va–c. Treatment of IVa–c with ethyl bromoacetate in ethanol under reflux in the presence of potassium hydroxide solution led to the formation of N‐(4‐chlorophenyl)‐7‐methyl‐3‐oxo‐5‐(aryl)‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxamide derivative VIII a–c in a single‐step synthesis. On the other hand, compound IVa reacted with α‐halo carbonitriles, namely, chloro acetonitrile, and monobromo malononitrile, to produce directly thiazolo[3,2‐a]pyrimidine derivatives Xa and Xb, respectively, Compound Xb also reacted with each of formic acid, formamide, and ammonium thiocyanate to form thiazolodipyrimidine derivatives XI–XIII, respectively. Compound VIIIa–c coupled with arenediazonium salts in pyridine to give the corresponding 2‐arylhydrazo derivatives XVIa–e. Compounds IV a–g and VIIIa–c were resynthesized under microwave irradiation. Some of the newly synthesized compounds were tested for their antimicrobial activities.