A facile approach for synthesis of thiazines-, thiazoles- and triazoles-annulated 6-styryl-2-thiouracil derivative

Abstract

Utility of 4-oxo-6-styryl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile 1 in synthesis of a new series of fused pyrimidines was described. Pyrimido[2,1-b][1,3]thiazines 6–9 were obtained via Michael addition of compound 1 to the polarized systems 2–5 in the presence of nanosized ZnO. S-alkylation of pyrimidine 1 followed by cyclization with phenacyl bromide, monochloroacetic acid, chloroacetonitrile and oxalyl chloride afforded the desired thiazolo[3,2-a]pyrimidines 10–13. Hydrazinolysis of compound 1 followed by addition cyclization with acetic anhydride, formic acid, carbon disulfide and benzoyl chloride afforded triazolo[4,3-a]pyrimidines 15–18. The antimicrobial screening showed high activity for thiazolo[3,2-a]pyrimidines 11 and 12 against both Gram (+ ve) and Gram (− ve) bacteria.