Titanium(III) chloride and electrochemical reduction of pyrazine, quinoxaline and triazine derivatives and of their salts

Armand, Joseph; Chekir, Khaled; Pinson, Jean

doi:10.1002/jhet.5570170618

Cited by 21 publications

(3 citation statements)

References 14 publications

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“…Phenazine itself can be readily reduced to 5,10-dihydrophenazine which is unstable in air, and such reduced phenazines readily reduce ferric (hydr)oxides, which may play an important role in the iron uptake . Pyrazine and quinoxaline heterocycles have established redox characteristics, where they can be reduced in aqueous solutions both electrochemically and with titanium(III) chloride and can undergo two one-electron transfers . Pyrazine is completely reduced to piperazine by nickel–aluminum alloy and quinoxaline can also be reduced to 1,4-dihydroquinoxaline, − which appears to be stable in air.…”

Section: Resultsmentioning

confidence: 99%

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

2019

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The anaerobic oxidation of methane (AOM) mitigates the flux of methane from marine sediments into the water column. AOM is performed by anaerobic methanotrophic archaea (ANME) that reverse the methanogenesis pathway and partner bacteria that utilize the released reducing equivalents for sulfate reduction. Here, we investigated small-molecule extracts from sediment-free thermophilic enrichment cultures of ANME-1 and sulfate-reducing bacteria using ultraperformance liquid chromatography with high-resolution mass spectrometry. During the analysis, we discovered a novel thioquinoxalinol-containing redox molecule as a major component of the chemically derivatized small-molecule pool. This compound contains both a redox active quinoxaline heterocyclic ring and a thiol group. Additionally, the same core structure was identified that contains a sulfate ester on the hydroxyl group, which likely makes the molecule more water soluble. Hydrated versions of both structures were also observed as major compounds in the extracts. On the basis of reactions of model compounds such as quinoxalin-6-ol, the hydrated version appears to be formed from the addition of water to the dehydropyrazine ring followed by an oxidation. These thioquinoxalinol compounds, which represent completely new structures in biochemistry, may be involved in electron transport processes within and/or between ANME-1 and sulfate-reducing bacteria, may serve protective roles by reacting with toxic compounds such as hydrogen sulfide, or may transport sulfate as a sulfate ester into the sulfate-reducing bacteria.

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Section: Resultsmentioning

confidence: 99%

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

2019

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“…An abundance of synthetic methods have been developed for the construction of these useful heterocycles 30. Among them, the selective reduction of quinoxaline derivatives is still the most employed approach, but requires toxic or expensive reducing reagents, such as lithium aluminium hydride,31 sodium borohydride,32 titanium chloride,33 indium powder,34 and borane 35…”

Section: Resultsmentioning

confidence: 99%

Selective N‐Alkylation of Arylamines with Alkyl Chloride in Ionic Liquids: Scope and Applications

et al. 2012

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An efficient N-selective alkylation of primary aromatic\ud amines in molten quaternary ammonium salts, as the solvent,\ud under relatively mild and base-free conditions is presented.\ud On the basis of the Kamlet–Taft parameters and the nucleophilicity\ud of the IL (ionic liquid) anions, the influence of the ionic liquid was evaluated. This protocol was validated on a\ud larger multigram scale and with the syntheses of bioactive\ud heterocycles (e.g., 1,4-benzothiazine and quinoxalines) and\ud new efficient MALDI matrixes

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“…In fact, we found a significant amount of starting quinoxaline unconsumed by LAH even after increasing the stipulated reaction time to six to twelve hours. More recently, the use of titanium chloride [6] or indium powder [7], yields mixtures of stereoisomers and offer no experimental improvement. We were considerably more intrigued by sporadic reports over the last three decades that featured the use of various boron reagents for the reduction of the diazine ring in the quinoxaline system.…”

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confidence: 98%

A rapid and efficient method for the reduction of quinoxalines

McKinney

Jackson

Salvatore

et al. 2005

Journal of Heterocyclic Chem

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Mono and di-substituted alkyl and aryl quinoxalines are rapidly reduced in high yield to their respective 1,2,3,4-tetrahydro-derivatives by borane in THF solution. In the case of the 2,3-di-substituted compounds, reduction is stereoselective yielding exclusively the cis-isomers. Sodium borohydride in acetic acid also reduces alkyl and aryl quinoxalines, but proceeds with lower yields and often produces side products. Sodium borohydride in ethanol reduces quinoxaline and 2-methylquinoxaline in high yield; however, the reaction is very slow, whereas 2,3-dialkyl and 2-aryl quinoxalines are not efficiently reduced by sodium borohydride in ethanol. [3]. One approach to obtaining these compounds is direct reduction of the parent quinoxalines. Classical reagents for the conversion of quinoxalines to 1,2,3,4-tetrahydroquinoxalines include lithium aluminum hydride [4] and catalytic hydrogenation [4,5]. Both methods proceed with moderate to good yields but require substantial purification procedures and extended reaction times. In fact, we found a significant amount of starting quinoxaline unconsumed by LAH even after increasing the stipulated reaction time to six to twelve hours. More recently, the use of titanium chloride [6] or indium powder [7], yields mixtures of stereoisomers and offer no experimental improvement. We were considerably more intrigued by sporadic reports over the last three decades that featured the use of various boron reagents for the reduction of the diazine ring in the quinoxaline system. However, results from these prior studies were somewhat difficult to interpret. For example, pyridine-borane in acetic acid solution at room temperature after seven hours was shown to reduce 1a in 95% yield, while trimethylamine-borane was apparently ineffective [8]. Subsequently, 2-aminopyrimidine-borane was used for this same transformation [9] but the reported yield was only 54%. Use of the borohydride ion has a similar history. In 1973, Rao stated [10] that quinoxaline was unaffected by sodium borohydride in methanol, but showed that this reagent in acetic acid reduced quinoxalines in moderate to good yields, in the presence of an electron-withdrawing substituent on the fused benzene ring. Later papers demonstrated that both potassium borohydride in carboxylic acid media [11] and sodium cyanoborohydride with benzyl chloroformate in methanol [12] effectively reduced 1a but were accompanied by, respectively, alkyaltion or acylation at nitrogen.We report herein that borane in THF rapidly converts 1a-f to 2a-f (Scheme 1). As demonstrated in Table I, the reactions proceed in excellent yields and the reductions involving 1c and 1f are highly stereoselective, resulting in the syn addition of hydrogen to give 2c and 2f. We also examined sodium borohydride as a reducing agent for 1a-f and are now able to clarify prior ambiguities. In ethanol, sodium borohydride slowly reduces 1a and 1b to give excellent yields of 2a and 2b. In addition, we have extended the procedure of Rao [10] by using sodium borohydride in acetic a...

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Titanium(III) chloride and electrochemical reduction of pyrazine, quinoxaline and triazine derivatives and of their salts

Cited by 21 publications

References 14 publications

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

Selective N‐Alkylation of Arylamines with Alkyl Chloride in Ionic Liquids: Scope and Applications

A rapid and efficient method for the reduction of quinoxalines

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