5-hydroxy-4,5-dihydropyrazoles

Зеленин, K. Н.; Alekseyev, V. V.; Tygysheva, Alja R.; Yakimovitch, S. I.

doi:10.1016/0040-4020(95)00672-u

Cited by 27 publications

(7 citation statements)

References 5 publications

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“…Similar tautomerism for the non-coordinated compounds is known for the series of 5-hydroxy-4,5-dihydropyrazoles [8], however linear isomers can be detected only in polar solvents (like DMSO) or in case of strong electron withdrawing substituents in the hydropyrazole moiety. As the tautomeric rearrangement 6 fi 7 is irreversible, the driving force of the transformation seems to arise from the decrease of steric hindrance due to formation of longer and flexible linker between C 10 terpenoid unit and bulky Os 3 (CO) 10 (l-S-) cluster fragment.…”

Section: Resultsmentioning

confidence: 89%

Triosmium clusters with bridging terpenic thioureato-like ligands

Кирин

Максаков

Вировец

et al. 2004

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 89%

Triosmium clusters with bridging terpenic thioureato-like ligands

Кирин

Максаков

Вировец

et al. 2004

Journal of Organometallic Chemistry

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“…However, the strongly electron-withdrawing nature of the α,β-diketone used in the synthesis led to the isolation of a stable intermediate, a dihydropyrazole (Scheme I), that when dehydrated, should furnish the pyrazole. The synthesis of the dihydropyrazole has previously been reported (Yakimovich et al, 2002;Zelenin et al, 1995). The fivemembered dihydropyrazole ring of C 10 H 9 F 3 N 2 O is approximately planar, the ring being buckled at the methylene carbon, and its phenyl substituent is aligned at 14.7 (2)° ( (Table 1) to generate a helical chain running along the b axis of the monoclinic unit cell (Fig.…”

Section: Data Collectionmentioning

confidence: 98%

“…For the synthesis, see: Yakimovich et al (2002); Zelenin et al (1995). For two related structures, see: Dias & Goh (2004); Yang & Raptis (2003).…”

Section: Related Literaturementioning

confidence: 99%

5-Hydroxy-3-phenyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazole

et al. 2011

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“…It has been shown that 1,3-diketone hydrazones form stable 5-hydroxy-2-pyrazolines only if an electron-withdrawing group, i.e. acyl, is at the 1-position, or if a perfluoroalkyl group is present at the 5-position of the pyrazoline ring 8. Synthesis of the series of stable 3-(2-arylvinyl)-5-hydroxy-5-phenyl-1-tosyl-2-pyrazolines 2a-f expands our knowledge about structure-stability dependence of 5-hydroxysubstituted pyrazolines.…”

mentioning

confidence: 99%

Synthesis of 5-Hydroxy- and 5-Amino-1-tosyl-5-phenyl-3-(2-arylvinyl)-4,5-dihydropyrazoles

Kuz’menok¹,

Koval'chuk²,

Zvonok³

2005

Synlett

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The reaction of b-arylacryloyloxiranes with tosylhydrazine leads to unexpected 5-hydroxysubstituted D 2 -pyrazolines. A series of 3-styryl substituted pyrazoles and 5-amino-D 2 -pyrazolines were synthesized from the 5-hydroxy-D 2 -pyrazolines. The mechanism of this process has been proposed based on current and previous results.The reaction of hydrazine and its derivatives with a,b-unsaturated ketones and a,b-epoxy ketones is one of the preparative methods for the synthesis of pyrazolines and pyrazoles. Pyrazolines are typical products of these reactions, when a,b-unsaturated ketones are used, and 4-hydroxy pyrazolines in the case where a,b-epoxy ketones are applied. 1 Combination of the functionalities of the barylacryloyloxiranes allowed evaluation of the reactivity of the carbonyl group, oxirane ring and conjugated double bond to nucleophilic reagents such as hydrazine. Earlier, we found that the reaction of b-arylacryloyloxiranes with hydrazine gives the oxiranylpyrazoline intermediates, stable enough for isolation. However, in solution these compounds undergo further intramolecular oxidative-reductive transformation to b-hydroxyalkylpyrazoles. 2 These data indicate that hydrazine reacts preferentially with the conjugated double bond of barylacryloyloxiranes. Reaction of phenylhydrazine with b-arylacryloyloxiranes in proton solvents gives b-arylvinylpyrazoles, which shows participation of the oxirane ring in the cyclization process. 3 In this paper, the reaction of b-arylacryloyloxiranes with tosylhydrazine is reported. Pyrazoles and pyrazolines with aromatic substituents are interesting as potential bioreceptor ligands. 4 Although 4-hydroxypyrazolines are the typical products of the reaction of a,b-epoxy ketones with tosylhydrazine 5 and other hydrazines, 1 we found that the reaction of 3-aryl-1-(3-phenyloxiran-2-yl)-prop-2-en-1-ones (1a-f) with tosylhydrazine under acid catalysis leads to formation of 3-(2-arylvinyl)-5-hydroxy-5-phenyl-1-tosyl-2-pyrazolines (2a-f) with 58-83% yield (Scheme 1). Additionally, 3-(2-arylvinyl)-5-phenyl-1-tosyl-1H-pyrazoles (3a-f) were isolated with 7-21% yield by chromatography after crystallization of the major products. 6The structures of 5-hydroxy-3-styrylpyrazolines (2a-f) were determined by IR, 1 H NMR and 13 C NMR spectroscopy. 7 Thus, the hydroxyl, azomethine and vinyl group absorptions were observed in IR spectra, but there was no presence of the carbonyl band. The 1 H NMR spectra indicated the presence of the methylene diastereotopic protons at d = 3.20-3.50 ppm (J = 17.6-17.9 Hz), consistent with 5-hydroxypyrazoline structures. 8,9 The chemical shift of the double bond protons appeared in the range of d = 6.55-6.66 ppm and 6.92-7.14 ppm (J = 16.4-16.7 Hz). Compared to the initial enones, they are displayed at the higher field as an ABsystem. The tosyl group protons are shown in the 1 H NMR spectrum as a characteristic singlet at d = 2.4 ppm (for the methyl group) and AB-system of aromatic protons signals in the low field at the range of d = 7.22 and 7.68 ppm (J = 8.3 ...

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5-hydroxy-4,5-dihydropyrazoles

Cited by 27 publications

References 5 publications

Triosmium clusters with bridging terpenic thioureato-like ligands

Triosmium clusters with bridging terpenic thioureato-like ligands

5-Hydroxy-3-phenyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazole

Synthesis of 5-Hydroxy- and 5-Amino-1-tosyl-5-phenyl-3-(2-arylvinyl)-4,5-dihydropyrazoles

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5-hydroxy-4,5-dihydropyrazoles

Cited by 27 publications

References 5 publications

Triosmium clusters with bridging terpenic thioureato-like ligands

Triosmium clusters with bridging terpenic thioureato-like ligands

5-Hydroxy-3-phenyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazole

Synthesis of 5-Hydroxy- and 5-Amino-1-tosyl-5-phenyl-3-(2-arylvinyl)-4,5-­dihydropyrazoles

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Synthesis of 5-Hydroxy- and 5-Amino-1-tosyl-5-phenyl-3-(2-arylvinyl)-4,5-dihydropyrazoles