Synthesis and some reactions of 2-mercapto-4-hydroxypyrimidine [3,4-(b)under-bar]coumarin

2-Mercapto-4-hydroxypyrimidine[3,4-b]coumarin (3) was prepared by the conde nsation of 3-ethoxycarbonylcoumarin (1) with thiourea. Alkylation of 3 with alkyl halides (namely, methyl iodide, ethyl iodide, benzyl chloride and et hyl chloroacetate) yielded the corresponding 2-alkylthio-4-hydroxypyrimidin e[3,4-b]coumarin 4a-d. Hydrolysis of 4d with 2 N NaOH gave acid derivative 6, and condensation of 4d with hydrazine hydrate gave hydrazone 7. 1,3,4-Ox adiazol derivatives 9 and 11 were obtained by the reaction of 7 with aromat ic aldehydes to give aryldene derivatives 8a,b. Cyclization of 8 followed w ith bromine in acetic acid and treatment of 7 with ethyl chloroformate in p yridine and sodium acetate led to 11.