Opianic acid reacts with various hydrazines to yield either hydrazone (3, 6) or phthalazinone (4) derivatives depending upon the electronic properties of the substituent attached to the hydrazine molecule. Oxidative cyclization of opianic acid aroylhydrazones with iodine and yellow mercuric oxide gave the 1,3,4‐oxadiazole derivatives 21. The aroylhydrazones were also condensatively cyclized by heating with acetic anhydride to give the 1,3,4‐oxadiazoline derivatives 24. Structures assigned to the prepared compounds were corroborated by studying their chemical as well as their spectral characteristics.
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