Synthesis Of Pyrazines Research Articles

Clean and Green Approach for One-pot Synthesis of Pyrazines from Ethylenediamine and 1, 2-Diketone or Its Analogues Under Neat Reaction Condition

Clean and Green Approach for One-pot Synthesis of Pyrazines from Ethylenediamine and 1, 2-Diketone or Its Analogues Under Neat Reaction Condition

Visible-Light-Mediated Synthesis of Pyrazines from Vinyl Azides Utilizing a Photocascade Process

A convenient method for the synthesis of substituted pyrazines from vinyl azides has been developed. This method is enabled by a dual-energy and electron-transfer strategy by visible-light photocatalysis. Initially, vinyl azides are activated by a triplet sensitization process from an excited ruthenium photocatalyst in the presence of water to form dihydropyrazines, followed by a single-electron-transfer (SET) process under oxygen (air) atmosphere that leads to the tetrasubstituted pyrazines in good to excellent yields.

Conversion of Tobacco Biomass to Flavor Components by Means of Microwave and Parr Reactors

Summary In the present work, microwave and Parr reactors were utilized for synthesis of pyrazines from plant-based biomass in the presence of ammonia and different amino acids. Using these techniques led to synthesis of a relatively wide range of pyrazines with sweet odor and chocolate-like smell. The optimum synthetic conditions to have maximum pyrazine yield for both the microwave and Parr reactions were 41 g of fructose/glucose syrup derived from cellulosic biomass, 28 mL NH4OH (30%), and 0.96 g L-threonine, 0.56 g L-valine, 0.5 g L-leucine, and 0.5 g L-isoleucine at 120 °C for 30 min. Quantitative results obtained via gas chromatography-mass spectrometry (GC-MS) using the traditional open-heated oil bath method have been compared with data obtained via microwave and Parr reactors. In these two latter methods, sealed vessels under high pressure and higher temperature were used. The yield of synthesized pyrazines increased dramatically with both microwave and Parr reactors. Surprisingly, the yield of synthesized pyrazines was both reproducible and nearly two times higher via the Parr reactor than that observed with the microwave reactor under comparable conditions.

Alkyl pyrazine synthesis via an open heated bath with variable sugars, ammonia, and various amino acids.

Semi-quantitative characteristics of headspace volatile pyrazines which constituted around 1% by weight of the final product have been previously described. The influence of reactant concentration, reaction temperature, and reaction time on both the yield of total alkyl pyrazines and the distribution pattern of specific identified pyrazines has not been reported. The optimum synthetic conditions were 5 mol L-1 NH4 OH, 2 mol L-1 rhamnose, 0.5 mol L-1 leucine at 110°C for 2 h. The greatest total amount of pyrazines obtained was 17 280 µg of extracted product which translated into 31% 2,6-dimethyl pyrazine, 17% 2-methyl pyrazine, 15% 2-ethyl-6-methyl pyrazine, and 16% 2-isoamyl-6-methyl pyrazine. The yield of synthesized pyrazines increased at higher temperatures. Quantitative total and specific pyrazine results as opposed to analysis of only headspace volatiles are more representative of pyrazine synthesis. © 2016 Society of Chemical Industry.

Synthesis of pyrazine via chemoselective reduction of β-keto-α-oximino ester using baker’s yeast

The synthesis of pyrazines by the baker’s yeast-mediated reaction of β-keto-α-oximino esters and amides is described. Baker’s yeast reduced oximes selectively over ketones of β-keto-α-oximino esters to give the corresponding β-keto-α-amino ester intermediates, which underwent spontaneous dimerization followed by air-induced aromatization to yield pyrazines. The chemoselective reduction of β-keto-α-oximino amides using baker’s yeast also afforded the corresponding pyrazines. Interestingly, both hydroximes and alkoximes gave the pyrazines by the baker’s yeast-mediated reduction via the corresponding amino ketones, the known precursors of pyrazines. The reaction was strongly dependent upon pH of reaction medium, and gave optimum yields at pH 5. These results demonstrate that pyrazines were synthesized efficiently and eco-friendly using a whole-cell biocatalytic system as an alternative to chemical reduction.

ChemInform Abstract: Synthesis of Pyrazines from Rhodium‐Catalyzed Reaction of 2H‐Azirines with N‐Sulfonyl 1,2,3‐Triazoles.

AbstractA new and efficient method for the synthesis of trisubstituted pyrazines is developed.

ChemInform Abstract: Iodine‐Mediated Oxidative Annulation for One‐Pot Synthesis of Pyrazines and Quinoxalines Using a Multipathway Coupled Domino Strategy.

An efficient iodine-mediated oxidative annulation of aryl acetylenes–arylethenes–aromatic ketones with 1,2-diamines for the synthesis of pyrazines and regioselective synthesis of quinoxalines is presented. A multipathway coupled domino approach has been developed for the one-pot synthesis of 1,4-diazines with high functional group compatibility.

Synthesis of pyrazines from rhodium-catalyzed reaction of 2H-Azirines with N-sulfonyl 1,2,3-triazoles.

An efficient synthetic route to a wide range of trisubstituted pyrazines is developed from Rh-catalyzed reaction of 2H-azirines with N-sulfonyl-1,2,3-triazoles through the elimination of nitrogen molecule and arylsulfinic acid. The present reaction proceeds through formation of in situ generated dihydropyrazines.

Synthesis of unsymmetrical pyrazines based on α-diazo oxime ethers.

Synthesis of unsymmetrically substituted pyrazines has been a challenge. The reactivity of α-imino carbenoids derived from α-diazo oxime ethers has been exploited for pyrazine synthesis, in which the reaction of α-diazo oxime ethers with 2H-azirines provides highly substituted pyrazines in good to excellent yields.

I2/Cu-mediated self-sorting domino reaction of aryl β-ketoesters into symmetrical 2-carboalkoxy-1,4-enediones: application to synthesis of pyrazine, β-carboline and quinoxalines

A self-sorting domino reaction of aryl β-ketoesters into symmetrical 1,4-enediones is reported by an I2/Cu system.

Iodine-mediated oxidative annulation for one-pot synthesis of pyrazines and quinoxalines using a multipathway coupled domino strategy.

An efficient iodine-mediated oxidative annulation of aryl acetylenes-arylethenes-aromatic ketones with 1,2-diamines for the synthesis of pyrazines and regioselective synthesis of quinoxalines is presented. A multipathway coupled domino approach has been developed for the one-pot synthesis of 1,4-diazines with high functional group compatibility.

Synthesis of Pyrazine Substituted 1,3,4-Thiadiazole Derivatives and Their Anticonvulsant Activity

The synthesis of new pyrazine substituted 1,3,4-thiadiazole derivatives was carried out in good yield by the reaction of pyrazine substituted 1,3,4-thiadiazoles with various sulfonyl chlorides. A chemical structure of all the new compounds was confirmed by ¹H NMR and mass spectral data. The new compounds were screened for their anticonvulsant activity against maximal electroshock (MES) seizure method. Rotarod method was employed to determine the neurotoxicity. Few compounds showed significant changes in anticonvulsant activity. The same compounds showed no neurotoxicity at the maximum dose administered (100 mg/kg).

Controlled synthesis of MoO3 microcrystals by subsequent calcination of hydrothermally grown pyrazine–MoO3 nanorod hybrids and their photodecomposition properties

We present our results on successful synthesis of pyrazine–MoO3 nanorod hybrids by using pyrazine and MoO3 nanorods. On the first stage, MoO3 nanorods were grown hydrothermally and, on the second stage, their mixture with pyrazine was again involved in a hydrothermal reaction to produce organic–inorganic hybrids. To understand the growth mechanism of the hybrids we varied time and temperature of the hydrothermal process. Intercalation of pyrazine was confirmed through X-ray diffraction analysis, X-ray photoelectron spectroscopy, X-ray emission spectroscopy, scanning electron microscopy methods. Upon calcinations, pyrazine was deintercalated, i.e. removed from the MoO3 hybrid system, and the MoO3 nanorods were found to bind together resulting in formation of MoO3 microslabs with increased surface area. Photodecomposition performance of the MoO3 nanorods, pyrazine–MoO3 hybrids and MoO3 microcrystals was studied against Procion Red MX-5B textile dye. A high photodecomposition performance was found to decrease when going from MoO3 nanorods to MoO3 microcrystal and, further, to pyrazine–MoO3 hybrids.

ZrOCl2·8H2O in water: An efficient catalyst for rapid one-pot synthesis of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines

Abstract Zirconium(IV) oxide chloride was found to be a rapid and efficient catalyst for the synthesis of pyrazines and 2,3-disubstituted quinoxalines in water. A variety of pyridopyrazine and 2,3-disubstituted quinoxaline derivatives are readily prepared in high yields under green conditions by cyclocondensation of the desired 1,2-diamine and 1,2-diketone using a catalytic amount of zirconium(IV) oxide chloride in water. Less active diamines, such as 2,3- and 3,4-diaminopyridines took part in this protocol to provide the desired products in good to excellent yields.

Greener approach toward one pot route to pyrazine synthesis

A very simple, cost effective, and environmentally benign method has been reported for the preparation of pyrazine derivatives of pentacyclic triterpenoids. The versatility of the method is determined by synthesizing a large number of pyrazine derivatives of smaller molecules.

The Cephalostatins. 22. Synthesis of Bis-steroidal Pyrazine Pyrones

Cephalostatin 1 (1), a remarkably strong cancer cell growth inhibitory trisdecacyclic, bis-steroidal pyrazine isolated from the marine tube worm Cephalodiscus gilchristi, continues to be an important target for practical total syntheses and a model for the discovery of less complex structural modifications with promising antineoplastic activity. In the present study, the cephalostatin E and F rings were greatly simplified by replacement at C-17 with an α-pyrone (in 12), typical of the steroidal bufodienolides, and by a dihydro-γ-pyrone (in 16). The synthesis of pyrazine 12 from 5α-dihydrotestosterone (nine steps, 8% overall yield) provided the first route to a bis-bufadienolide pyrazine. Dihydro-γ-pyrone 16 was synthesized in eight steps from ketone 13. While only insignificant cancer cell growth inhibitory activity was found for pyrones 12 and 16, the results provided further support for the necessity of more closely approximating the natural D-F ring system of cephalostatin 1 in order to obtain potent antineoplastic activity.

Mechanochemical synthesis of pyrazine:dicarboxylic acid cocrystals and a study of dissociation by quantitative phase analysis

Cocrystals of pyrazine with dicarboxylic acids were synthesised by mechanochemical methods. Crystal structure determination was performed by single crystal and powder X-ray diffraction (PXRD). The cocrystals consist of infinite 1D hydrogen-bonded chains exploiting the familiar pyridine-carboxylic acid synthon. The kinetics of dissociation of the pyrazine:phthalic acid cocrystal was studied at non-ambient conditions using PXRD and quantitative Rietveld phase analysis. We show that the dissociation process is both temperature and humidity dependent providing useful information about a possible dissociation mechanism.

Zwitterion-Induced Synthesis of Pyrazines and Pyrazolopyridazines

Zwitterion-Induced Synthesis of Pyrazines and Pyrazolopyridazines

Pb(NO3)2 Mediated Synthesis of Pyrazine.

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Pb(NO3)2 Mediated Synthesis of Pyrazine

AbstractLead nitrate was used as an efficient catalyst in the oxidation and condensation reaction of hydroxy ketone with diamine leading to the formation of pyrazine derivatives in excellent yields.