Pyrazines and their Benzo Derivatives

Sato, Nobuhiro

doi:10.1016/b978-008096518-5.00119-2

Cited by 30 publications

(13 citation statements)

References 345 publications

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“…1 Although rarely described in nature, synthetic quinoxaline ring is a part of a number of antibiotics which are known to inhibit the growth of Grampositive bacteria and are also active against various transplantable tumors. 2 From the synthesis standpoint, despite remarkable efforts in the last decade, [3][4][5][6][7] the development of effective methods for the synthesis of quinoxaline is still an important challenge. By far, the most common method relies on the condensation of an aryl 1,2-diamine with a 1,2-dicarbonyl compound in refluxing ethanol or acetic acid for 2-12 h. For example, the condensation of 1,2-diaminobenzene with benzil provides quinoxaline 1a in literature yields ranging from 34-85% depending on the reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Benign approaches for the microwave-assisted synthesis of quinoxalines

Mohsenzadeh

Aghapoor

Darabi

2007

J. Braz. Chem. Soc.

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Neste trabalho foram usados dois sistemas simples, rápidos (3 min) e versáteis, de transferência de energia de microondas, na ausência de solventes, para a síntese de quinoxalinas (2,3-difenilquinoxalina e seus derivados, 2,3-difenil-4a,5,6,7,8,8a-hexahidroquinoxalina, 2-fenilquinoxalina, piridina-2,3-diamina e 2,3-dihidro-5,6-difenilpirazina). O primeiro método consiste no uso de suportes minerais na reação de 1,2-dicarbonil (benzil) ou α-hidroxicetona (aciloína) com 1,2-diaminas. Entre os suportes minerais, a eficiência da alumina ácida como catalisador foi claramente comprovada (80-86%). Além disso, apresenta um papel importante na oxidação de aciloína ao correspondente sistema 1,2-dicarbonílico. O segundo método consiste no uso de microondas em mistura dos reagentes 1,2-dicarbonil(benzil) e 1,2-diaminas. O excelente rendimento dos produtos (90-97%) e a simples lavagem com água e filtração na ausência de solventes orgânicos fazem desse sistema uma ótima alternativa para a prevenção de poluição, em um processo ambientalmente benigno. Embora os dois métodos tenham sido planejados para evitar passos adicionais de purificação, o último é um processo mais limpo com tratamento reacional mais simples.Two benign, simple, rapid (3 min), solvent-free and versatile microwave energy transfer systems for the synthesis of quinoxalines, i.e. 2,3-diphenylquinoxaline and its derivatives, 2,3-diphenyl-4a,5,6,7,8,8a-hexahydroquinoxaline, and 2-phenylquinoxaline and also pyridine-2,3-diamine and 2,3-dihydro-5,6-diphenylpyrazine have been used. The first approach consists on the use of mineral supports on the reaction of 1,2-dicarbonyl (benzil) or α-hydroxyketone (acyloin) with 1,2-diamines. Among mineral supports, the efficiency of acidic alumina as catalyst was clearly proved (80-86%). Moreover, it has an oxidative role in the tandem oxidation of acyloin to the corresponding 1,2-dicarbonyl. The second approach is the use of polar paste system on the reaction of 1,2-dicarbonyl (benzil) with 1,2-diamines. The excellent products yield (90-97%) and simple washing with water and filtration in the absence of organic solvent makes it an impressive alternative green platform. Although both methods implemented in this study have been designed to circumvent additional purification steps, the latter is cleaner with an easier work-up.

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Section: Introductionmentioning

confidence: 99%

Benign approaches for the microwave-assisted synthesis of quinoxalines

Mohsenzadeh

Aghapoor

Darabi

2007

J. Braz. Chem. Soc.

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“…The evidence for the structures of all di(hetero)aryl-substituted dihydropyrazines has been obtained by means of 1 H and 13 C NMR spectroscopy, and X-ray crystallography analysis performed for racemic 1-ethyl-5-phenyl-6-thiophen-2-yl-1,6-dihydropyrazine-2,3-dicarbonitrile (11a), 1-ethyl-5-thiophen-3-yl-6-thiophen-2-yl-1,6-dihydro-pyrazine-2,3-dicarbonitrile (11c) and 1-ethyl-5-phenyl-6-thiophen-3-yl-1,6-dihydropyrazine-2,3-dicarbonitriles (12a) (Figs. 1-3).…”

Section: Methodsmentioning

confidence: 99%

“…11 It is known that the addition reaction of 1,4-diazines and their benzo derivatives is of great importance for the synthesis of biologically active compounds, including alkaloids. [12][13][14][15][16][17] In order to cause these transformations azaaromatic compounds are usually activated by quaternization to obtain N-alkyl-1,4-diazinium salts. 17,18 Indeed, it has recently been shown that 1-alkyl-1,4-diazinium cations are prone to add carbo-and heteroatomic nucleophiles to give mono-and diadducts, or to be transformed into condensed tetrahydropyrazines through the tandem addition reactions with bifunctional nucleophiles.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, X-ray crystal structure and antimycobacterial activity of enantiomerically pure 1-ethyl-2,3-dicyano-5-(het)aryl-6-hetaryl-1,6-dihydropyrazines

Verbitskiy¹,

Toporova²,

Кодесс³

et al. 2014

Arkivoc

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The Petasis reaction of 6-alkoxy adducts of 1-alkyl-2,3-dicyano-5-arylpyrazinium salts with aromatic boronic acids, such as 2-thienylboronic, 2-furanylboronic and 3-thienylboronic acids, or their benzo analogs in dichloromethane proceeds smoothly at room temperature with the formation of the corresponding 5-aryl-6-hetaryl substituted 1,6-dihydropyrazine derivatives. All dihydropyrazines were separated as pure enantiomers by chiral HPLC, and their absolute configurations for each pair of enantiomers have been determined by X-ray analysis. Individual enantiomers were screened in vitro for their antimycobacterial activities against Mycobacterium tuberculosis H 37 Rv, avium, terrae and extensively drug-resistant and multi-drug-resistant strains isolated from tuberculosis patients in Ural region (Russia). It has been shown that several compounds exhibit a good level of antituberculosis activity compared to the reference drugs.

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“…In the core part of many agrochemicals and pharmaceuticals were found quinoxaline ring. (Sakata et al 1988;Sato et al 1996;Seitz et al 2002;Gazit et al 1996) Similarly, it was found that quinoxaline ring also exists in antibiotics, such as actinomycin, levomycin, and echinomycin (Brown et al 2004) . Its derivatives have been used as anti-viral (Lindsley et al 2005) and anticancer agents (Loriga et al 1997).…”

Section: Introductionmentioning

confidence: 99%