Green and high efficient synthesis of triaza‐benzo[b]fluoren‐6‐one derivatives in water under microwave irradiation

Shao, Qingqing; Tu, Shu‐Jiang; Li, Chunmei; Cao, Lushuai; Zhou, Dianxiang; Zhang, Yan; Hao, Wen‐Juan; Wang, Qian

doi:10.1002/jhet.5570450218

Cited by 27 publications

(4 citation statements)

References 23 publications

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“…Synthesis of quinazolinone analogs (4a-n). >300 [31] (Continued) [31] 5 70 92 >300 >300 [31] 6 85 88 >300 >300 [50] (Continued) 303-305 [31] (Continued) [31] 14 65 94 >300 307-309 [31] and 13 C NMR (100 MHz) spectra were recorded on a Bruker spectrometer using dimethylsulfoxide (DMSO-d 6 ) as solvents and tetramethylsilane (TMS) as an internal standard at IISC, Bangalore. The chemical shifts were given on the δ scale (ppm).…”

Section: Methodsmentioning

confidence: 99%

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

Beerappa

Shivashankar

2016

Synthetic Communications

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Section: Methodsmentioning

confidence: 99%

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

Beerappa

Shivashankar

2016

Synthetic Communications

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“…The first of these consists of decomposition of E into aminopyrazole I and 2-R 2 -methylidenecyclohexane-1,3-dione E which give rise to adduct G, while the second pathway is the rearrangement E → G. Analogous schemes were proposed for the reaction of 2-aminobenzimidazole with aldehydes and cyclohexane-1,3-dione in water under microwave activation [21] and for the three-component condensation of aldehydes with aromatic amines and dimedone [22].…”

Section: Ia Idmentioning

confidence: 97%

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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“…The synthesis of benzo [4,5]imidazo [1,2-a]pyrimidine derivatives has been considered of great interest to organic chemists because of their pharmacological and therapeutic properties such as antineoplastic [1], protein kinase inhibitor [2], T cell activation [3], TIE-2 and/or VEGFR2 inhibitory activities [4]. The most common methods for the preparation of benzo [4,5]imidazo [1,2-a]pyrimidine derivatives is the one-pot three-component condensation reactions of β-dicarbonyl compounds, aldehydes and 2-aminobenzimidazole in the presence of, 1,1,3,3,N,N,N',N'-tetramethylguanidinium trifluoroacetate (TMGT) [5], sulfamic acid [6], microwave [7][8][9]. Other methods involve the reaction of β-ketoester with aldehyde followed by condensation with 2-aminobenzimidazole to give the target products [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Silica sulfuric acid promoted one-pot synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine derivatives under solvent-free conditions

Yan

Yang

2010

Bull. Chem. Soc. Eth.

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Green and high efficient synthesis of triaza‐benzo[b]fluoren‐6‐one derivatives in water under microwave irradiation

Cited by 27 publications

References 23 publications

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

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

<b>Silica sulfuric acid promoted one-pot synthesis of benzo[4,5]imidazo[1,2-<i>a</i>]pyrimidine derivatives under solvent-free conditions</b>

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