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

Abstract

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