Synthesis of some novel isoxazolyl pyrimido[4,5-d][1,3]-thiazol-7-ones, isoxazolyl-2-(4-oxo-4H-1,3-benzothiazin-2-yl)acetamides and isoxazolyl thiazolidinones from isoxazolyl cyanoacetamide synthon

The synthesis or title compounds has been achieved from isoxazolyl cyanoacetamide 2 synthon. Isoxazolyl cyanoacetamide 2 has been obtained by reaction of 4-amino-3-methyl-5-styrylisoxazole 1 with ethyl cyanoacetate. The cyclocondensation of 2 with aryl isothiocyanates in presence of sulphur followed by subsequent reaction with acetic anhydride afforded isoxazolylpyrimido[4,5-d][1,3]-thiazol-7-ones 4a-i. Compounds 2 have been converted to isoxazolyl 2(4-oxo-4/H,3-benzothiazin-2-yl)acetamides 5a-f by treatment with 2-sulfonyl benzoic acid in boiling acetic acid. Cyclocondensation of 2 with thioglycolic acid in boiling acetic acid furnishes isoxazolyl thiazolidinoncs 6a-f in excellent yields. The newly synthesized compounds 2-6 have been characterized by IR, (1)H NMR and mass spectral studies.