2.6- Dimethyl-3-ethylpyrazines

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... 

Alkylpyrazines, which are commonly produced in the mandibular glands of ants and wasps (1 ), appear to have a limited distribution in the venoms of ants. 2,5-Dimethyl-3-ethylpyrazine (XXII) has been identified as a trace constituent in the venom of Atta sexdens (15), a myrmicine species that also produces a pyrrole (X) as a poison gland product. 

Cocoa Butter Cocoa butter is one of the most Uked and highly prized food ingredients because of its desirable flavor and unique melting behavior. As early as 1961, van Elzakker and van Zutphen (32) studied and identified 23 volatile compounds in the vacuum steam distillate of cocoa butter. Later, Rizzi (33) identified nine alkylpyrazines including methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-5-methylpyrazine, trimethylpyra-zine, 2,5-dimethyl-3-ethylpyrazine, 2,6-dimethyl-3-ethylpyrazine, and tetramethyl-pyrazine in the basic fraction of a vacuum steam distillate of cocoa butter. 

In the pyrazine series, the Mannich reaction was applied first to 2,5-dimethyl-pyrazine by Linder and Spoerri (715). Of the amines tried, positive reactions were obtained only with dime thy lamine, piperidine, and morpholine, and it was found that one, or more usually two, of the hydrogen atoms of each of the methyl groups could be substituted. Thus 2,5-dimethylpyrazine, dimethylamine hydrochloride, and formalin in refluxing isopentyl alcohol gave 2,5-bis[bis(dimethylaminomethyl)-methyl]pyrazine and 2,5-bis(j3-dimethylaminoethyl)pyrazine. Reaction of 2-methyl-pyrazine with formalin and diethylamine hydrochloride gave 2- 3-diethylamino-ethylpyrazine (716) similarly dimethylamine hydrochloride gave 2-dimethyl-aminoethylpyrazine (17) and some 2-[bis(dimethylaminomethyl)]methylpyrazine (18) (657). 

A patent (726) has described the preparation of 2methyl-pyrazine by reaction with ammonia and air at 350° over a catalyst containing vanadium pentoxide and potassium sulfate a series of cyanomethylpyrazines has been prepared from the corresponding methylpyrazines by reaction with sodium amide in liquid ammonia followed by Af-methyl-A -phenylcyanamide in dioxane (644). 2-Hydroxyiminomethylpyrazine has been prepared from 2-methylpyrazine, sodium amide, and liquid ammonia with butyl nitrite (727, 728), and 2-hydroxy-iminomethyl-3,6-dimethyI-5-pentylpyrazine similarly from 2,3,5-trimethyl-6-pentylpyrazine (648). Nitrones (28) have been prepared from 23-and 2,5-dimethyl-and tetramethylpyrazine through the substituted methylpyridinium (perchlorates) (27) by reaction with p-nitroso-A, fV-dimethylaniline (729). Dehydrogenation of ethylpyrazine at 600° over a calcium cobaltous phosphate catalyst gives 2-vinyl-pyrazine (658). 

Hydroxy-, 2-hydroxy-3-methyl-, 2diydroxy-3,6-dimethyl-(3diydroxy-2,5-di-methyl-), and 2-hydroxy-3-ethylpyrazines have been prepared by hydrolysis of the corresponding isodiazotate salts (3) in cold 40% aqueous sulfuric acid in 42-72%... 

Amino-5-bromomethyl-3-cyanopyrazine with ethyl acetoacetate and sodium hydride in tetrahydrofuran gave 5-[(2 -acetyl-2 -ethoxycarbonyl)ethyl]-2-amino-3-cyanopyrazine (1031) [which with sodium chloride in aqueous dimethyl sulfoxide at 155-170° for 6 hours gave 5-(2 -acetylethyl)-2-amino-3-cyanopyrazine] and a similar reaction with ethyl y-ethoxyacetoacetate gave 2-amino-3-cyano-5-[(2 -ethoxycarbonyl-2 -ethoxymethylcarbonyl)ethyl]pyrazine [which with sodium chloride in aqueous dimethyl sulfoxide at 155-170° for 6 hours gave 2-amino-3-cyano-5-(2 -ethoxymethylcarbonyl)ethylpyrazine] (1031). 

Acid extraction yielded the following pyrazine derivatives tetramethylpyra-zine, 2,6-diethyl-3-methylpyrazine (47), 2,3-dimethyl-5-ethylpyrazine, 2-methoxy-3-isopropoxy-5-methylpyrazine, and 2,6-dimethoxy-3-isopropoxy-5-methylpyra-zine.38 All structures were confirmed by synthesis. Pyrazine derivatives had previously been isolated from green peas (Pisum sativum).39... 

Pyrazine, 2-ethyl-3,5-dimethyl-, 2-ethyl-3,5-dimethylpyrazine, 2,6-dimethyl-3-ethylpyrazine 113925-07-0] FEMA 3150... 

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