Synthesis of Heterocycle Compounds Containing Two Pyridazinone Units

Four novel compounds containing two pyridazinone units attached to one benzene or pyridine ring, protected and deprotected 1,5-di[3(2H)-pyridazinon-6-yl]benzene and 2,6-di[3(2H)-pyridazinon-6-yl]pyridine were synthesized in eight steps, which provided a useful method for the preparation of pyridazinone derivatives via the Stetter and cyclization reactions. Their structures were characterized by 1H NMR, 13C NMR, and HRMS.