Pyrazine, 2-Methyl

Other reactions with their counterparts in the pyridine series are also well known. Thus, 2,3-dimethylpyrazine 1,4-dioxide reacts with acetic anhydride to yield 2,3-bis(acetoxy-methyl)pyrazine (S3) in good yield (72KGS1275). Pyrazine 1-oxide also reacts directly with acetic anhydride to yield 2(ljH)-pyrazinone by way of the intermediate acetate (Scheme 22). The corresponding reaction in the quinoxaline series is not so well defined and at least three products result (Scheme 23) (67YZ942). 

Methyl pyrazine-2-carboxylic acid is refluxed with thionyl chloride in anhydrous benzene for approximately 12 hours. Benzene and thionyl chloride excess is removed by distillation. Then some anhydrous dioxane is added and this acid chloride solution is allowed to drop into p-(/3-aminoethyl)-benzenesulfonamide suspension in dioxane and anhydrous pyridine. The resulting mixture is then refluxed for 3 hours. Dioxane is removed by distillation and then the residue is washed with water and acetic acid. The raw acylated sulfonamide is then filtered and crystallized from 95% ethanol, thus obtaining a product of MP 200 to 203 C. 

CjjHjjOj 35363-65-6) see Dimethisterone methyl pyrazine-2-carboxylate (QH N202 6164-79-0) see Pyrazinamide 5-methyl-2-pyrazinecarboxylic acid (QHfiN202 5521-55-1) see Adpimox Glipizide 5-methylpyrazine-2-carboxylic acid see under 5-methyl-2-pyrazinecarboxylic acid... 

Although methylation of 2(l//)-pyrazinones with diazomethane gives a mixture of O- and N-methylated pyrazines as the fixed tautomers (Equation 20) <1993JOC7542>, the trimethylsilylation leads to the exclusive formation of 0-silyl compounds, which are effectively converted to bromopyrazines 42 (Scheme 33) <1999JHC783>. In the same... 

With chiral racemic oxiranes one enantiomer reacts faster than the other the degree of kinetic resolution is very high for L-valine/alanine-based dialkoxydihydropyrazines. For example, in the reaction of one equivalent of (2.S )-2,5-dihydro-2-isopropyl-3,6-dimethoxy-5-methyl-pyrazine (1, R1 = CH3) with two equivalents of fW-(//,/ )-2,3-dimethyloxirane (R2,R4 = CH3 R = H) virtually only the (2//,3/ )-oxirane enantiomer reacts with the lithiated dihydropyrazine to give exclusively the (l /, 2/, 2 / )-configuratcd adduct i.e., (2/ ,5S)-2,5-dihydro-5-isopropyl-3,6-dimethoxy-2-[(l/ ,2/ )-2-(2-methoxyethoxymethoxy)-l-methylpropyl]-2-methylpyrazine, entry 7. Likewise, kinetic resolution (intramolecular) occurs upon reaction with rac-7-oxabicy-clo[4.1.0]heptane (entry 8). 

Beim kurzen Erhitzcn in waBriger Natronlauge dehydratisiert 3-Amino-2-(amino-benzoyloxi-mino-methyl)-pyrazin in guter Ausbeute zu 3-(3-Amino-2-pyrazinyl)-2-phenyl-l,2,4-oxadi-azol (77% Schmp, 220-2230)211 ... 

At elevated temperatures, sugars react more quickly than at lower temperatures with aqueous ammonia, to give, mainly, substituted imidazoles and pyrazines, summarized in Table IV, and a catalyst is not needed. At the higher temperatures, there is an increase in the methyl-pyrazine and -imidazole fractions and a decrease in the (hydroxymethyl)imidazole and (tetrahydroxybutyl)pyrazine fractions, indicating occurrence of thermal cleavage of the side chains.10... 

Oxidation, by nitric acid, 48 of aldehyde to carboxyl group, 49 of hydroxyl to carboxyl group, 49 of 2-methylquinoxaline to 2-methyl-pyrazine-5,6-dicarboxylic acid, 89 of quinoxaline to 2,3-pyrazinedicar-boxylic acid, 87... 

Bourguignon and coworkers in their preparation of thieno[2,3-6]pyrazine used methyl-pyrazine (364 Scheme 107) (80JHC257) as starting material. The chlorination of (364) yields 2-chloro-3-methyl- and 2-chloro-6-methyl-pyrazine in a ratio of 80 20. Without separation this mixture is treated with ethyl mercaptoacetate in the presence of sodium ethoxide to give (365) in 91% yield (based on 2-chloro-3-methylpyrazine). Oxidation of the methyl group to an aldehyde function and subsequent base catalyzed ring closure yields (366), which is transformed to (363) by the method depicted already in Scheme 106. 

Methoxy-3-isopropyl-5-methyl-pyrazine OCH3 i-C3H7 ch ... 

Methoxy -3-isopropyl-6-methyl-pyrazine OCH3 i-C3H7 ch3... 

Methoxy-3-acetyI-6-methyl- pyrazine OCHj COCHj ch3... 

Isobutyl-2-methoxy-3-methyl -pyrazine OCHj CH3 i-C4H9 ... 

Ethoxy-5-iso butyI-3-methyl-pyrazine oc2h5 ch i-c4h9 ... 

O Like 2-methylamino-3-methyl-pyrazine but more green and peanut-like, less cocoa notes O 180 ppb/water s 64... 

Quantitatively, dimethylpyrazine production was also lower, suggesting fewer available carbonyl fragments or less desirable conditions exist for formation of dimethyl versus unsubstituted or methyl pyrazine. 

Quantitatively, dimethylpyrazine production was also lower, suggesting fewer available carbonyl fragments and mechanistically less desirable conditions exist for formation of dimethyl versus unsubstituted or methyl pyrazine. A linear relationship of hi< i correlation was found to exist between pH and the rate of formation of pyrazines, with r2 values of 0.974 and 0.999 for pyrazine and 2-methylpyrazine, respectively. Effect of pH on yield was investigated under standard conditions (2 hr heat treatment at 95°C). pH was found to have a great effect on yield, with a total of 13,000 ppb pyrazines produced at pH 9.0 and only 24 ppb at pH... 

Ethyl-3-methyl pyrazine 2-Ethyl-6-methyl pyrazine + + +... 

Concentrations of thermally generated meat flavor components are diminished by protein adsorption when soy extenders are added to fresh meat products before heating. The amounts of individual alkyl pyrazines, thermally generated by heating beef diffusate, decreased linearly as the amount of whole soy, soy 7S or soy 11S proteins were increased in a model system. Similar recoveries were obtained when pyrazines were mixed with soy either as chemical standards or from diffusate. Stoichiometry and energetics of interaction were determined for methyl pyrazine congeners with soy proteins at 120° and 145°C. Results of this study suggest that flavorants can be added in readily determined amounts to compensate for losses due to adsorption in meat-soy products. 

In this study the physical parameters involved in interaction of a major class of meat flavorants, methyl pyrazines, with soy proteins were determined at meat roasting temperatures. Beef diffusate, the water soluble, low molecular weight fraction that constitutes about IX of beef, was shown to contain the necessary precursors to obtain a desirable, thermally generated meat aroma (8). Diffusate was heated under controlled conditions and generated volatiles were transferred to a gas chromatograph for separation and quantitation. Methyl pyrazines, either from heated diffusate or from standard solutions, were measured in the presence of purified soy proteins and the thermodynamics of binding were determined. 

There was no loss in flavorant at a 100 mg level when either whole soy or soy 7S protein was used, but there was a 14-24 percentage loss when 11S protein was used. Only soy 11S protein affected the substituted pyrazine content of the mixture at all addition levels. The higher the substituted pyrazine congener, the smaller was the percentage loss with any of the protein types. At the 500 mg level, only about 50% of the amount of any of the methyl pyrazines in the control was recovered from either soy 7S or 11S protein while 70% was recovered from whole soy protein. These results greatly extend the initial work reported by Palkert and Fagerson (11J who determined that about 75% of dimethyl thiazole, a sulfur-nitrogen heterocycle, was recovered from dry, textured soy protein. 

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