α-Aminoazoles in syntheses of heterocycles. 3(5)-Aminopyrazole-4-carbonitriles in the synthesis of pyrazolo[1,5-α]pyrimidines

Emelina, E. E.; Петров, А. А.; Firsov, A. V.

doi:10.1134/s1070428007030281

Cited by 12 publications

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References 8 publications

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“…The 13 C NMR spectra of VIIIc and VIIId contained doublet signals in the region δ C 146 -147 ppm ( 1 J CH = 188 Hz). Comparison with the data for model pyrazolopyrimidines [25][26][27][28] possessing N=C 5 H-C (δ C 148.5-149 ppm) and N-C 7 H=C fragments (δ C 134.2-135 ppm) showed that molecules VIIIc and VIIId possess an N=C 5 H-C fragment and a cyclohexene ring fused at the C 6 -C 7 bond of the pyrazolo[1,5-a]pyrimidine core. The structure of compounds IXa-IXc and X-XIII unambiguously followed from the chemical shifts of carbon nuclei in the pyrimidine ring and methyl group and the corresponding data for the N-C(CH 3 )=C and N=C(CH 3 )-C fragments given in Table 2.…”

Section: Ia Idmentioning

confidence: 98%

“…The heterocyclic fragment α-AMINO AZOLES IN THE SYNTHESIS OF HETEROCYCLES: VI. a If a strong electron-withdrawing substituent (e.g., CN group) is present in position 3, the chemical shift is ~163-165 ppm [27]. N 1 C 2 C 3 C 3a N 4 C 4a C 8a C 9 N 10 is almost planar: the largest deviation from the mean-square plane is 0.041 Å (C 3 ).…”

Section: Ia Idmentioning

confidence: 99%

“…The structure of the synthesized compounds was determined on the basis of their elemental analyses, 1 H and 13 C NMR spectra, and X-ray diffraction data. The chemical shifts of carbon nuclei in the pyrimidine ring and methyl group were compared with the data reported by us previously [25][26][27] and those given in [28] ( Table 2). The 13 C NMR spectra of VIIIc and VIIId contained doublet signals in the region δ C 146 -147 ppm ( 1 J CH = 188 Hz).…”

Section: Ia Idmentioning

confidence: 99%

“…Characteristic 13 C chemical shifts of pyrazolo[1,5-a]pyrimidines[25][26][27][28] and compounds VIII-XVI…”

mentioning

confidence: 99%

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α-Amino azoles in the synthesis of heterocycles: VI. Synthesis and structure of cycloalkane-annulated pyrazolo[1,5-a]pyrimidines

et al. 2009

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Reactions of 4-aryl-1H-pyrazol-5(3)-amines with 2-acylcycloakanones and 2-acyl-5,5-dimethylcyclohexane-1,3-diones led to the formation of regioisomeric 6,7,8,9-tetrahydropyrazolo[1,5-a]quinazoline, 5,6,7,8-tetrahydropyrazolo[5,1-b]quinazoline, and 7,8-dihydro-6H-cyclopenta[e]pyrazolo[1,5-a]pyrimidine derivatives. The product structure was determined by X-ray analysis and 1 H and 13 C NMR spectroscopy. * For communication V, see [1]. Extensive development of synthetic approaches to polyfunctional pyrazolo[1,5-a]pyrimidine derivatives is stimulated by the fact that compounds possessing pyrazole and pyrimidine fragments are promising as potential biologically active substances. Several efficient medical agents exhibiting sedative and soporific activity (such as Zaleplon [2], Indiplon [3], and Ocinaplon [4]) are known; some compounds of this series have been patented as antidiabetic [5] and antiphlogistic agents [6], antidepressants [7], and analgesics [8,9]. Pronounced biological activity of pyrazolo-[1,5-a]pyrimidine derivatives was noted in [10][11][12][13][14][15][16][17].The goal of the present work was to study regioselectivity in the formation of cycloalkane-annulated pyrazolo[1,5-a]pyrimidines and determine characteristic 13 C NMR spectral parameters of particular regioisomers. We examined reactions of 5(3)-amino-4-aryl-1H-pyrazoles Ia-Id with 2-acylcycloalkanones III-VII and three-component condensation of 5(3)-amino-4-aryl-1H-pyrazoles Ia and Id with dimedone and aldehydes.Aminopyrazoles I reacted with 2-ethoxymethylidene-5,5-dimethylcyclohexane-1,3-dione (II) and 2-acetyl-5,5-dimethylcyclohexane-1,3-dione (III) to give only substituted 6,7,8,9-tetrahydropyrazolo-[1,5-a]quinazolines which may be regarded as pyrazolopyrimidines fused at the C 6 -C 7 bond to cyclohexene ring. The reaction begins with nucleophilic attack by the amino nitrogen atom of pyrazole I at the carbon atom of the ethoxymethylidene or acetyl group in II or III, respectively. In the first case, the primary linear adduct, 5,5-dimethyl-2-{[(3-methyl-4-phenyl-1H-pyrazol-5-yl)amino]methylidene}cyclohexane-1,3-dione (A), was isolated as individual substance, while in the second case, 3-hydroxy-5,5-dimethyl-2-{1-[(4-phenyl-1H-pyrazol-3-yl)imino]ethyl}cyclohex-2-en-1-one (B) was detected as intermediate product by 1 H NMR (Scheme 1). The formation of an analogous intermediate compound was observed previously in the reaction of 5-methoxymethylidene-2,2-dimethyl-1,3-dioxane-4,6-dione with 5(3)-aminopyrazoles [18]. In the 1 H NMR spectrum of compound A, the NH proton in the pyrazole ring resonated at δ 12.82 ppm, and the exocyclic CH= and NH protons gave doublets at δ 8.65 and 12.76 ppm, respectively, with a coupling constant 3 J of 13.1 Hz. The downfield position of the latter NH signal indicates formation of intramolecular hydrogen bond NH · · · O. The structure of intermediate B was determined by 1 H NMR monitoring of the reaction of aminopyrazole Id with acetyldimedone III in DMSO-d 6 at 20°C. After 2 days, the 1 H NMR spectrum of the reaction...

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Section: Ia Idmentioning

confidence: 98%

Section: Ia Idmentioning

confidence: 99%

Section: Ia Idmentioning

confidence: 99%

“…Characteristic 13 C chemical shifts of pyrazolo[1,5-a]pyrimidines[25][26][27][28] and compounds VIII-XVI…”

mentioning

confidence: 99%

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α-Amino azoles in the synthesis of heterocycles: VI. Synthesis and structure of cycloalkane-annulated pyrazolo[1,5-a]pyrimidines

et al. 2009

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“…Pyrazole dyes are prepared either by coupling of diazopyrazoles with a suitable coupler or by coupling aromatic and heteroaromatic diazonium salts with pyrazolones 1,2 or aminopyrazoles. [3][4][5][6][7][8] Cyclization of 1,3-bifunctionally substituted-2-arylhydrazones by hydrazines have been extensively employed. We have investigated the possible utility of the Gabriel approach for the synthesis of amino acids from alkyl halides and indolidenedione for the synthesis of both heteroaromatic amines and 2-arylhydrazono-1,3-bifunctional pyrazole precursors with methylamino substituents.…”

Section: Introductionmentioning

confidence: 99%

Microwave-assisted organic synthesis: the Gabriel approach as a route to new pyrazolylhydrazonoazoles

Al‐Mousawi¹,

El‐Apasery²,

Al-Kanderi³

2008

Arkivoc

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The pyrazole 7 was diazotized in the presence of hydrochloric acid in acetic acid to give in situ the diazonium chloride 9. The latter was coupled with malononitrile to afford 2-pyrazolylhydrazonomesoxalonitrile 10, which could be converted into aminopyrazolone 11 by reaction with hydrazine hydrate. The phenylhydrazone 13 reacted with hydroxylamine hydrochloride to afford the oxime 18 that could be readily converted into the nitrile 19 either by refluxing in a solution of sodium acetate in acetic acid or by heating in a microwave oven (MW). Compound 19 reacted with hydroxylamine hydrochloride to give amidooxime 20 either by refluxing in dioxane or by heating in MW.

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α‐Aminoazoles in Syntheses of Heterocycles. 3(5)‐Aminopyrazole‐4‐carbonitriles in the Synthesis of Pyrazolo[1,5‐a]pyrimidines.

2007

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Fused pyrimidine derivatives R 0515 α-Aminoazoles in Syntheses of Heterocycles. 3(5)-Aminopyrazole-4-carbonitriles in the Synthesis of Pyrazolo[1,5-a]pyrimidines. -A procedure for the regioselective synthesis of substituted 7-aryl-5-methylpyrazolo[1,5-a]pyrimidines (III) that are structurally related to the sedative and soporitic drug Zaleplon is described. -(EMELINA, E. E.; PETROV, A. A.; FIRSOV, A. V.; Russ. J. Org. Chem. 43 (2007) 3, 471-473; St. Petersburg State Univ., St. Petersburg 198504, Russia; Eng.) -D. Singer 36-147

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α-Aminoazoles in syntheses of heterocycles. 3(5)-Aminopyrazole-4-carbonitriles in the synthesis of pyrazolo[1,5-α]pyrimidines

Cited by 12 publications

References 8 publications

α-Amino azoles in the synthesis of heterocycles: VI. Synthesis and structure of cycloalkane-annulated pyrazolo[1,5-a]pyrimidines

α-Amino azoles in the synthesis of heterocycles: VI. Synthesis and structure of cycloalkane-annulated pyrazolo[1,5-a]pyrimidines

Microwave-assisted organic synthesis: the Gabriel approach as a route to new pyrazolylhydrazonoazoles

α‐Aminoazoles in Syntheses of Heterocycles. 3(5)‐Aminopyrazole‐4‐carbonitriles in the Synthesis of Pyrazolo[1,5‐a]pyrimidines.

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