2-methoxy-3-methyl pyrazine

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

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... 

Benzyl-6-methoxy-5-methyl-2-pyrazinamine 2-Benzyl-3-methoxy-6-methyl pyrazine 2-Benzyl-6-methoxy-3-methylpyrazine... 

Both 2-methylpyrazine 1- and 4-oxides (625) (obtained by oxidation of 2-methyl-pyrazine with peroxyacetic acid) on treatment with phosphoryl chloride have been claimed to give 2-chloro-3-methylpyrazine(626)but the 2-methylpyrazine-4-oxide used is now known to have been a mixture of the 1- and 4-isomers (734). More recently other workers (735, 736) have claimed that the mixed 2-methylpyrazine 7V-oxides with phosphoryl chloride gave a mixture of 2-chloro-3-, -5-, and -6-methylpyrazine but Nakel and Haynes (686) have shown that 2-methylpyrazine 1-oxide with phosphoryl chloride followed by sodium methoxide gave 2-methoxy-3-methylpyrazine and 6-methoxy-2-methylpyrazine, and 2-methylpyrazine 4-oxide (3-methylpyrazine 1-oxide) similarly treated gave only 2-methoxy-6-methylpyrazine. 3-Trifluoromethylpyrazine 1-oxide with benzenesulfonyl chloride at 1(X)° has been shown to give 2-chloro-6-trifluoromethylpyrazine (44%) (759). 

The first lithiopyrazine derivative was prepared by Hirschberg et al. (1015) from 3-iodo-2,5-dimethylpyrazine and butyllithium in ether subsequent reaction with (a) carbon dioxide gave 3-carboxy-2,5-dimethylpyrazine, and (b) several aromatic aldehydes gave the carbinols (62, R = H, p-methoxy, m-nitro) (1015). Similar reactions were observed when 2-formylpyridine and 2-acetylpyridine (1016) were used as the carbonyl compounds, but with acetaldehyde attempted reactions were unsuccessful (1015). A patent also describes the preparation of many carbinols from 2,5-disubstituted 3-iodopyrazines (164). The lithio reagent derived from 3-iodo-2,5-dimethylpyrazine (with butyllithium in hexane) with 2-nitrobenzaldehyde gave 2,5-dimethyl-3[ 1 -hydroxy-1 (2"-nitrophenyl)methyl] pyrazine (1017). 

Pyrazine, 2-(3-furanyl)-5-methyl-Pyrazine, methoxy-Pyrazine, 3-methoxy-2-methyl-... 

Musty/mouldy aroma defects in black pepper are caused by a mixture of 2,3-diethyl-5-methyl-pyrazine and 3-isopropyl-2-methoxy-pyrazine. Some samples of white pepper contain up to 2.5 mg/kg of skatole (odor threshold on starch 0.23 pg/kg), which together with 3- and 4-methylphenol can cause a fecal aroma defect. This aroma defect arises during fermentation (degradation of amino acids, e. g., tryptophan 3-methylindole), which is carried out to remove the flesh. On longer storage, this defect becomes more noticeable because intensive aroma substances, which disguise it in fresh white pepper, volatilize. 

Hodgetts KJ, Ge P, Yoon T, Lombaert SD, Brodbeck R, GuUaneUo M, Kieltyka A, Horvath RF, Kehne JH, Krause JE, Maynard GD, HofEman D, Lee Y, Fung L, Doller D (2011) Discovery ofN-(l-ethylpropyl)-[3-methoxy-5-(2-methoxy-4-trifluoromethoxyphenyl)-6-methyl-pyrazin-2-yl]amine 59 (NGD 98-2) an orally active corticotropin releasing factor-1 (crf-1) receptor antagonist. J Med Chem 54 4187-4206... 

Pyrazine, 2-methoxy-3-sulfanilamido-plasma half-life, 1, 162 Pyrazine, methyl-chlorination, 3, 168 oxidation, 3, 168 reactions... 

Amino-3-Methoxy-5-Bromo-Pyrazine 7 grams of 2-amino-3,5-dibromo-pyrazine are boiled for 9 hours in a methanolic solution of sodium methylate (obtained from 0.65 gram of Na and 18.5 ml of methanol). By cooling a crystalline product is obtained, filtered and washed once with methanol and 2 to 3 times with water. The yield is 5.4 grams, melting at 138°C. 

Substituted pyrimidine N-oxides such as 891 are converted analogously into their corresponding 4-substituted 2-cyano pyrimidines 892 and 4-substituted 6-cya-no pyrimidines 893 [18]. Likewise 2,4-substituted pyrimidine N-oxides 894 afford the 2,4-substituted 6-cyano pyrimidines 895 whereas the 2,6-dimethylpyrimidine-N-oxide 896 gives the 2,6-dimethyl-4-cyanopyrimidine 897 [18, 19] (Scheme 7.6). The 4,5-disubstituted pyridine N-oxides 898 are converted into 2-cyano-4,5-disubsti-tuted pyrimidines 899 and 4,5-disubstituted-6-cyano pyrimidines 900 [19] (Scheme 7.6). Whereas with most of the 4,5-substituents in 898 the 6-cyano pyrimidines 900 are formed nearly exclusively, combination of a 4-methoxy substituent with a 5-methoxy, 5-phenyl, 5-methyl, or 5-halo substituent gives rise to the exclusive formation of the 2-cyanopyrimidines 899 [19] (Scheme 7.6). The chemistry of pyrimidine N-oxides has been reviewed [20]. In the pyrazine series, 3-aminopyrazine N-ox-ide 901 affords, with TCS 14, NaCN, and triethylamine in DMF, 3-amino-2-cyano-pyrazine 902 in 80% yield and 5% amidine 903 [21, 22] which is apparently formed by reaction of the amino group in 902 with DMF in the presence of TCS 14 [23] (Scheme 7.7) (cf. also Section 4.2.2). Other 3-substituted pyrazine N-oxides react with 18 under a variety of conditions, e.g. in the presence of ZnBr2 [22]. 

Geosmin, 2-Methyl isobomeol (MIB) and 2-isopropyl methoxy pyrazine are known to be produced by various types of actinomycete cultures (10-15). Geosmin and MIB are saturated tertiary alcohols and resist oxidation. The steric configuration of the hydroxyl and methyl groups in both compounds are believed to interact with receptors in the nose, imparting their characteristic earthy odour (16). The four compounds itemised as the key osmogenes in this odorous emission have extremely low odour threshold concentrations. Their occasional occurence in drinking water can lead to widespread complaints and are routinely monitored for within this Authority. 

Kinetic parameters k, often also and AS, occasionally AV ) for formation and dissociation of several pentacyanoferrate(II) complexes [Fe(CN)5L]" have been established. Ligands L include several S- and A-donor heterocycles,4-methyl- and 4-amino-pyridines, a series of alkylamines, 3- and 4-hydroxy- and 3- and 4-methoxy-pyridines, several amino acids, nicotinamide, " 4-pyridine aldoxime, 3-Me and 3-Ph sydnones, several bis-pyridine ligands,neutral, protonated, and methylated 4,4 -bipyridyl, 1,2-bis(4-pyridyl)ethane and traTO-l,2-bis0-pyridyl)ethene, pyrazine- 4,4 -bipyridyl- and bis(4-pyridyl)ethyne-pentaammine-cobalt(III), edta-ruthenium(III), and pentaammineruthenium-(II)and-(III) complexes of... 

The aposematic beetle, Metriorrhynchus rhipidius, contains three pyrazines as warning odor components and two amides as bitter principles (Tables III, V, and VIII) (97). Of the three components with the beetlelike odor, the most characteristic is 2-methoxy-3-isopropylpyrazine (24b). The other two components are 2-methoxy-3-methylpyrazine (24a) and 2-methoxy-3-sec-butylpyrazine (24d). It would seem likely that these compounds will occur in the defensive systems of the aposematic beetles. The two amide components, detectable in the hemo-lymph exuded by adult beetles, are 3-phenylpropanamide (130) and l-methyl-2-quinolone (57), the latter being the major component. It seems likely that these bitter principles contribute to distastefulness to potential predators. 

Methoxy-3-isobutylpyrazine 176 (Structure 4.53) is found in galbanum oil obtained from Ferula galbaniflua. 2,4-disubstituted pyridines 177, N,N-dimeth-ylated amino compounds 178, alkyl pyrazines 179, quinoline 180 and methyl quinolines 181 were isolated from fig leaf absolute [64]. 

Galbanum Ferula galbaniflua Boiss., F. rubricaulis Boiss. 2-Methoxy-3-isobutyl pyrazine, 5-sec-butyl-3-methyl-2-butenethioate, 1,3,5-undecatriene as minor components, and monoterpene hydrocarbons (75), sesquiterpene hydrocarbons (10), lactones umbeUic acid, umbeUiferone... 

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