1-Alkylpyrazoles and 1-alkyl-5-chloropyrazoles from halovinyl ketones and 1,1-dialkylhydrazines

Bozhenkov, G. V.; Savosik, V. A.; Клыба, Л. В.; Zhanchipova, E. R.; Мирскова, А. Н.; Levkovskaya, G. G.

doi:10.1134/s1070428008080150

Cited by 7 publications

(18 citation statements)

References 5 publications

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“…It was shown that the reactions involving 2-dimethylamino-substituted aryl, hetaryl, and dimethoxymethylvinyl ketones afforded only 1-tert-butyl-5-aryl(hetaryl)(formyl)-substituted pyrazoles (NMR and XRD data). These results are in agreement with the data of [33,34,38] where has been reported on the aryl 2-chlorovinyl ketones to react with alkylhydrazines and also with arylhydrazines giving only 1,3-disubstituted isomers. Yet in the reaction of hexyl (2-dimethylaminovinyl) ketone with tertbutylhydrazine under the same conditions a mixture formed of 1,5-and 1,3-isomers in the ratio 7 : 1.…”

Section: Methodssupporting

confidence: 95%

“…At the same time in the NMR spectrum of the closest analog of pyrazole 2a, 1-pentyl-3-propylpyrazole (4) the signals were observed at 5.99 (1H, Yet the assignment of the proton signals in [36] in the 1 Н NMR spectra of 1-tert-butyl-3-and -5-hexylpyrazoles contradicted our and the other data [33,40]. The Н 3 signal in the spectrum of 1-tert-butyl-5-hexylpyrazole appears upfield (7.20 ppm) from the Н 5 signal of the 1,3-isomer (7.21 ppm), although these signals are very close.…”

Section: Methodscontrasting

confidence: 80%

“…We showed in this study that under the conditions of the regioselective synthesis of 1,3-dialkylpyrazoles from alkyl 2-chlorovinyl ketones and unsymmetrical dialkylhydrazines [32,33] and of a mixture of isomeric 1,3-and 1,5-dialkylpyrazoles from alkyl chlorovinyl ketones and alkylhydrazines [34] the reactions of alkyl, haloalkyl 2-chlorovinyl ketones with tert-butylhydrazine also led to the formation of a mixture of 1,3-and 1,5-isomers of 2 and 3 dialkylpyrazoles (see the Table, Scheme 1). 1,5-Isomers 3 are evidently less feasible thermodynamically than the 1,3-substituted analogs 2.…”

Section: Methodsmentioning

confidence: 98%

“…Considering 1 Н NMR spectra it should be first of all mentioned that introducing the tert-butyl group in the position 1 of pyrazoles 2a-2e and 3a-3e significantly affects the position of the signals from the protons of the heterocycle as compared with the corresponding signals in the spectra of the other 1,3-and 1,5-dialkylpyrazoles [33,34]. For instance, we formerly observed that in 1,3-and 1,5-dialkylpyrazoles the positions of Н 4 signals in the 1 Н NMR spectra practically coincided (∆δ ≈ 0.01 ppm), and the signals of Н 3 protons appeared downfield with respect to those of Н 5 protons [16] (see the figure).…”

Section: Methodsmentioning

confidence: 99%

“…The probe of 1 µL volume was admitted at a split ratio 1 : 2. Initial 2-chlorovinyl ketones 1a-1e, among them previously unknown ketone 1e, were obtained from the chlorides of the respective acids and acetylene at the catalysis with anhydrous aluminum chloride [31,33,34,39]. Propyl 2,2-dichlorovinyl ketone 6 was synthesized from butyroyl chloride and 1,1-dichloroethylene by procedure [43].…”

Section: Mass Spectra Of Electron Impact Of Compounds 2-7mentioning

confidence: 99%

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Synthesis and structure of 1-tert-butyl-substituted 3(5)-alkylpyrazoles from 2-chlorovinyl ketones

et al. 2015

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Reactions of alkyl, halomethyl 2-chlorovinyl ketones with tert-butylhydrazine in the presence of triethylamine afford unsymmetrical 1-(tert-butyl)-3-and -5-disubstituted pyrazoles. The reaction direction is governed by the ketone ability of the nucleophilic substitution of chlorine and of the dehydrochlorination leading to acetylene ketones. 2-Chlorovinyl ketones react with tert-butylhydrazine along two routes giving mixtures of 1-(tert-butyl)-3-and -5-alkylpyrazoles. The content of 3-alkyl-1-(tert-butyl)pyrazole in the formed isomers mixture grows up to 73% with growing length of the alkyl chain of the ketone and up to 87 and 94% at introducing halogen atom in the alkyl fragment of the chloroenone.Pyrazole and its derivatives attract attention due to the widest range of their pharmacologic activity [1][2][3][4][5], versatile specific agrochemical properties [6][7][8][9]. The high interest in this class of heterocyclic compounds originates as well from their large potential in modern technologies of dyes in cosmetics, photography and production of fluorescent substances and stabilizers [1][2][3][4][5]. Compounds of the pyrazole series find application both in the large-scale and fine organic synthesis [1][2][3][4][5], in the supramolecular [10] and polymer chemistry [11, 12], as liquid crystls [13], ligands for metal complex catalysis [14][15][16], in designing complexes with uncommon magnetic properties [17,18].The practical utilization of pyrazoles and the extension of their application fields requires not only development of synthetic procedures for new pyrazole derivatives, but mainly the solution of an important task of working out directional procedures for preparation of individual isomers of unsymmetrically substituted pyrazoles. The analysis of the known approaches shows the especially promising application of haloenones as initial reagents for pyrazole synthesis [19][20][21][22][23], in particular, of their individual isomers. The systematic investigation of the reactivity of versatile haloenones [24][25][26][27][28][29] demonstrated that the reactions of 2,2-dihalovinyl ketones with unsymmetrical dialkylhydrazines, alkyl-, arylhydrazines under various condition resulted in the chemo-and regiospecific formation of 1-alkyl(aryl)-5-halo-3-alkyl(aryl)(haloalkyl)pyrazoles. Therewith the hydrazine character does not considerably affect the process direction.The preparation of 1,3-disubstituted pyrazoles with no halogen atoms in the ring from 2-chlorovinyl ketones is governed by the hydrazine structure. The regioselective synthesis of 1,3-disubstituted pyrazoles from 2-chlorovinyl ketones occurs at the use of 1,1-dialkyl-and arylhydrazines [29][30][31]. At the same time no formation of two isomers was observed in the reactions of 2-chlorovinyl ketones with hydrazines containing a long alkyl chain [32].In extension of the research on the development of syntheses of dialkyl-substituted pyrazoles we studied the reactions of a number of 2-chlorovinyl ketones with tert-butylhydrazine. The goal of the work consiste...

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Section: Methodssupporting

confidence: 95%

Section: Methodscontrasting

confidence: 80%

Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Mass Spectra Of Electron Impact Of Compounds 2-7mentioning

confidence: 99%

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Synthesis and structure of 1-tert-butyl-substituted 3(5)-alkylpyrazoles from 2-chlorovinyl ketones

et al. 2015

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ChemInform Abstract: 1‐Alkylpyrazoles and 1‐Alkyl‐5‐chloropyrazoles from Halovinyl Ketones and 1,1‐Dialkylhydrazines.

et al. 2009

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Pyrazole derivatives R 01801-Alkylpyrazoles and 1-Alkyl-5-chloropyrazoles from Halovinyl Ketones and 1,1-Dialkylhydrazines. -The regioselective heterocyclization of alkyl 2-chloro-and 2,2-dichlorovinyl ketones with 1,1-dialkylhydrazines to 1,3-dialkylpyrazoles and 1,3-dialkyl-5-chloropyrazoles, resp., involves the intermediate formation of dialkylhydrazones. -(BOZHENKOV, G. V.; SAVOSIK, V. A.; KLYBA, L. V.; ZHANCHIPOVA, E. R.; MIRSKOVA, A. N.; LEVKOVSKAYA*, G. G.; Russ. J.

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Access to gem-Dibromoenones Enabled by Carbon-Centered Radical Addition to Terminal Alkynes in Water Solution

et al. 2021

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We herein report a novel and more practical approach to prepare gem-dibromoenones from terminal alkynes, tetrabromomethane (CBr4), and water in a single step. Mechanistic studies reveal that the generation of a tribromomethyl radical with the assistance of a persulfate salt (K2S2O8) is essential to this transformation. The reaction features readily available chemicals, a broad substrate scope, a green solvent, and mild reaction conditions, providing an efficient alternative for construction of halogen-substituted enones.

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1-Alkylpyrazoles and 1-alkyl-5-chloropyrazoles from halovinyl ketones and 1,1-dialkylhydrazines

Cited by 7 publications

References 5 publications

Synthesis and structure of 1-tert-butyl-substituted 3(5)-alkylpyrazoles from 2-chlorovinyl ketones

Synthesis and structure of 1-tert-butyl-substituted 3(5)-alkylpyrazoles from 2-chlorovinyl ketones

ChemInform Abstract: 1‐Alkylpyrazoles and 1‐Alkyl‐5‐chloropyrazoles from Halovinyl Ketones and 1,1‐Dialkylhydrazines.

Access to gem-Dibromoenones Enabled by Carbon-Centered Radical Addition to Terminal Alkynes in Water Solution

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