Utility of a Pyrimidin-2-Thione Derivative in Synthesis of New Fused Thiazolo[3,2-a]pyrimidines

A pyrimidin-2-thione derivative 2 was prepared and treated with 1,2-dibromoethane, chloroacetic acid and ethyl chloroacetate to give the alkylation products 3,4,9,5, respectively. Furthermore, the reaction of 2 with acrylonitrile and hydrazine hydrate yielded the pyrimidino[2,1-b]thiazine derivative 7, and [1,2,4]-triazolo[4,3-a]pyrimidine 8. Compound 9 was used as the key starting material for synthesis of thiazolo[3,2-a]pyrimidine and pyrano[2',3' :4,5]thiazolo[3,2-a]pyrimidine derivatives 10-13, through the reaction with ethyl acetate, malononitrile, hydrazine hydrate, -aroylacrylic acid, and chalcone, respectively. Treatment of compound 5 with 3,5-dibromo-2-aminobenzoic acid in refluxing butanol gave the 3,1-benzoxazinone derivative 6. The structure assignment of the new compounds is based on chemical and spectroscopic evidence.