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. I29 ul. Br. Kashirinvkh, 454136 CheO,abinsk. Russian Federation A number of 1,4-dihydropyridazines and pyridazines were prepared by the Diets--Alder reaction with an inverse electron demand from cyclic heterodicne systems, 3.6-bisc3.5-dimethyl-4-R-pyrazol-l-yl)-1,2,4.5-tetrazines. :lnd some enamines :is well as from 4-vinytpyridine, butyl vinyl ether, phenylacetyiene, and ac~lamide. The reaction of 3.6-bis(3,5-dimethylpyrazol-I-yl/-l,2,4.5-tetrazme with styrene afforded 4,5-dihydropyridazine, which was readily oxidized by atmospheric oxygen to lbrm the corresponding pyridazine. Electron-withdrawing substituents (Br or CI) m the pyrazole rings accelerate [4+21-cycloaddition. When heated, 1,4-dihydropyridazines, which were synthesized from tetrazines and enamines, eliminated amine to give pyridazincs. The reactivities of tetrazines were evaluated by quantum-chemical methods.

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