Distinguishing Features of reactions of 2-chloro-and 2,2-dichloro(bromo)vinyl ketones with alkyl-and arylhydrazines |
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Authors: | G. V. Bozhenkov V. A. Savosik L. I. Larina L. V. Klyba E. R. Zhanchipova A. N. Mirskova G. G. Levkovskaya |
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Affiliation: | (1) Faworsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033, Russia |
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Abstract: | 2-Chlorovinyl alkyl ketones react with alkylhydrazines to give mixtures of 1-R-3-R′- and 1-R-5-R′-pyrazoles: The 1-R-3-R′-pyrazoles form through the heterocyclization of 2-chlorovinyl ketone alkylhydrazones whereas in the heterocyclization into 1-R-5-R′-pyrazoles N 1-alkyl-N 2-(2-acylvinyl)hydrazines are involved. The regiospecific heterocyclization of 2-chloro-and 2,2-dichlorovinyl ketones with arylhydrazines and also of 2,2-dichloro(bromo)vinyl trifluoromethyl ketones with C alkylhydrazines into pyrazoles and 5-chloro(bromo)-pyrazoles proceeds through a stage of haloenones hydrazones formation. The study of the structure of the obtained 1-alkyl-3(5)-alkylpyrazoles by means of two-dimenaional 1H and 13C NMR spectroscopy and GC-MS method made it possible to assign the proton and carbon signals of isomeric pyrazoles and to establish the diagnostic ions for the pair of 1,3-and 1,5-isomers. |
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