Synthesis of 4-(2-hydroxyphenyl)-1-phenyl-1,2,4-triazolidine-3,5-dione derivatives through cyclic transformations of 3-(2-phenylcarbazoyl)-2(3H)-benzoxazolone derivatives

Four 3-(3 -benzylidene-2-phenylcarbazoyl)-2(3H)-benzoxazolone derivatives 3 have been synthesized from benzoxazolone derivatives 1 and benzaldehyde N- chloroformylphenylhydrazone 2, By acid hydrolysis, these compounds yielded 3-(2-phenylcarbazoyl)-2(3H)benzoxazolone derivatives 4 which were not isola ted and were transformed via an intramolecular reaction into 4-(2-hydroxyph enyl)-1-phenyl-1,2,4-triazolidine3,5-dione derivatives 5 in a good yield. A ttempts to cyclize these compounds by intramolecular elimination of water i nto tricyclic compounds 6 with various dehydrating agents were unsuccessful .