synthesis of some 3-(thiazol-4-yl)-4-hydroxycoumarins

In this work, an easy and efficient procedure for the synthesis of eight 3-(thiazol-4-yl)-4-hydroxychromen-2-one derivatives is presented. 3-Acetyl-4-hydroxychromen-2-one (1) was brominated with phenyltrimethylammonium tribromide to afford 3-(2-bromoacetyl)-4-hydroxychromen-2-one (2). Compound 2 reacts with thiourea, thioacetamide and ammonium dithiocarbamate to afford 3-(2-aminothiazol-4-yl)-4-hydroxychromen-2-one (3), 4-hydroxy-3-(2-methylthiazol-4-yl)chromen-2-one (4a) and 4-hydroxy-3-(2-mercaptothiazol-4-yl)chromen-2-one (5), respectively. In a similar manner, compound 2 was treated with four mono-N-substituted thioureas and thiobenzamide to give the corresponding 3-(thiazol-4-yl)-4-hydroxychromen-2-one derivatives.