2- ethylpyrazine

Bromination using NBS has been used to provide acetylpyrazine derivatives from the corresponding ethylpyrazines. Bromination of 2-ethyl-3-methylpyrazine gives 2-bromoethyl-3-methylpyrazine in quantitative yield this may be oxidized using the sodium salt of 2-nitropropane or with pyridine AT-oxide to yield 2-acetyl-3-methylpyrazine in yields of 66 and 25% respectively (Scheme 14). 

Direct oxidation of ethylpyrazines to the corresponding acetylpyrazines may also be carried out in favourable circumstances using hot chromic acid (75JOC1178). Treatment of 2-ethyl-3-alkylpyrazines with chromic acid yields the corresponding 2-acetyl-3-alkyl-pyrazines in yields of 50-70%. In the absence of the 3-alkyl substituent the yields fall dramatically to less than 10%. Acetylpyrazines are more generally prepared by the inverse addition of a Grignard reagent to a cyanopyrazine. 

The Stille coupling of tetraethyltin and chloropyrazine 15 led to ethylpyrazine 16, which was an important intermediate for preparing quinuclidinylpyrazine derivatives as muscarinic agonists [13]. In this particular case, the reductive elimination took place faster than (3-hydride elimination. 

Kang Y, Hu M, Zhu Y, Gao X, Wang MW. (2009) Antioxidative effect of the herbal remedy Qin Huo Yi Hao and its active component tetram-ethylpyrazine on high glucose-treated endothelial cells. Life Sci 84 428-436. 

The genetic activity of pure synthetic Maillard products has also been studied. 2-Methylpyrazine, 2-ethylpyrazine, 2,5-di-methylpyrazine and 2,6-dimethylpyrazine all induced a significant increase in chromosome aberrations in Chinese hamster ovary cells... 

The use of an isotope dilution assay is the best method to quantify labile and low level odorants. He applied this technique to the determination of 2-acetyl-l-pyrroline and 2-methyl-3-ethylpyrazine, the two compounds which showed the highest FD-factors among the compounds with roasty odor notes in extracts from wheat or rye bread crust, respectively ( 7, 38). The results are summarized in Table III. The high level of the acetylpyrroline in the crusts of the wheat breads was striking compared to the level in the rye breads. These quantitative data confirm that 2-acetyl-l-pyrroline is a character impact odor compound of the wheat bread crust. 

The following synthesis (Scheme 15) of 2-ethylpyrazine, based on the reaction of ethylenediamine and 1,2-butylene oxide, is illustrative of the further application of these reactions.171... 

Pyrazinecarboxylic acid has been obtained by selenious acid oxidation in pyridine of methylpyrazine or aqueous permanganate oxidation of ethylpyrazine, in yields of 64 and 48%, respectively.171,218 It has also been obtained in 70% yield by partial decarboxylation of pyrazine-2,3-dicarboxylic acid on heating in vacuo at 210°.219 Aqueous permanganate oxidation of 2,5-distyrylpyrazine gives the 2,5-dicarboxylic acid.220 Pyrazine-2,5-dicarboxylic acid has also been prepared in 45% yield by direct carboxylation of pyrazine with carbon dioxide at 50 atm pressure at 250° for 3 hours in the presence of a potassium carbonate and calcium fluoride catalyst.221 Pyrazine-tricarboxylic acid (57), obtainable in only very poor yields by oxidation of 2,5-dimethyl-3-ethylpyrazine, is prepared in 87% yield by alkaline permanganate oxidation of 2-(D-arabo)tetrahydroxybutyl-quinoxaline (56).222 Decarboxylation of the tricarboxylic acid by... 

Acetamidoethyl)pyrazine 2-Acetamido-5-ethylpyrazine 2- Acetamido-6- ethylpyrazine 2-Acetamido-3-guanidinocarbonyl-5-isopropylaminopyrazine 2-Acetamido-3-guanidinocarbonyl-5-methoxyaminopyrazine 2-Acetamido-3-guanidinocarbonyl-5-methoxypyrazine... 

Chloro-6-(A-ethyl-A-methylamino)-3-guamdinocarbonyl-2-pyrazinamine 2-Chloro-3-ethyl-5-methylpyrazine 5-Chloro-6-(A-ethyl-A-propylamino)-3-guamdinocarbonyl-2-pyrazinamine 5 - Chloro- 6- (1 - ethy lpropyl )ami no-3-guanidinocarbonyl-2-pyrazinamine 2-Chloro-3-ethylpyrazine... 

Ethoxy-5,6-diphenyl-2-pyrazinecarbonitrile 2-Ethoxy-3-ethoxymethyl-6-methylpyrazine 2-(l-Ethoxyethyl)-3-ethylpyrazine 2-Ethoxy-3-ethylpyrazine... 

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