[4+2]-Cycloaddition of 3,6-bis(3,5-dimethyl-4-R-pyrazol-1-yl)-1,2,4,5-tetrazines with alkenes |
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Authors: | G L Rusinov R I Ishmetova N I Latosh I N Ganebnych O N Chupakhin V A Potemkin |
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Institution: | (1) Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, 20 ul. S. Kovalevskoy, 620219 Ekaterinburg, Russian Federation;(2) Chelyabinsk State University, 129 ul. Br. Kashirinykh, 454136 Chelyabinsk, Russian Federation |
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Abstract: | A number of 1,4-dihydropyridazines and pyridazines were prepared by the Diels-Alder reaction with an inverse electron demand
from cyclic heterodiene systems, 3,6-bis(3,5-dimethyl-4-R-pyrazol-1-yl)-1,2,4,5-tetrazines, and some enamines as well as from
4-vinylpyridine, butyl vinyl ether, phenylacetylene, and acrylamide. The reaction of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine
with styrene afforded 4,5-dihydropyridazine, which was readily oxidized by atmospheric oxygen to form the corresponding pyridazine.
Electron-withdrawing substituents (Br or Cl) in the pyrazole rings accelerate 4+2]-cycloaddition. When heated, 1,4-dihydropyridazines,
which were synthesized from tetrazines and enamines, eliminated amine to give pyridazines. The reactivities of tetrazines
were evaluated by quantum-chemical methods.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 354–360, February, 2000. |
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Keywords: | 1 2 4 5-tetrazine 1 4-dihydropyridazine pyridazine enamine Carboni-Lindsey reaction [4+2]-cycloaddition azadiene dienophile quantum-chemical calculations |
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