Syntheses of Diaryl sulfone. 6

It has been found by direct heating of bis[4-(1-methyl-3-carboxypropylidene)hydrazinophenyl] sulfone at 160° resulted in the cyclization to form bis[4-(3-methyl-6-oxo-1, 4, 5, 6-tetrahydropyridazino)phenyl] sulfone. The reaction took a different course when heated at 180-190° in the presence of zinc chloride as a catalyst and formed bis(2-methyl-3-carboxymethyl-5-indolyl) sulfone.