Synthesis of 2-Aryl[1]benzofuro[2,3-e][1,2,4]triazin-3(2H)-ones and Their Use for Preparation of 1-Aryl-5-(2-hydroxyphenyl)-6-azauracils

A series of arylhydrazones 1a-1i was prepared by coupling of arene diazonium salts with ethyl N-(benzo[ b ]furan-2-yl)carbamate. The hydrazones 1 were thermally cyclized to the corresponding 2-aryl[1]benzofuro[2,3- e ][1,2,4]triazin-3(2 H )-ones 2a-2i , derivatives of a new fused ring system. Compounds 2 were transformed by hydrolytic splitting to the corresponding 1-aryl-5-(2-hydroxyphenyl)-6-azauracils 3a-3i .