2- 6-methylpyrazine

Side chain reactivity is also enhanced and is typified by the difference in reactivity of 2-methylpyrazine and 2-methylpyrazine 1,4-dioxide towards anion formation and subsequent condensation reactions. 2-Methylpyrazine undergoes condensation with benzal-dehyde at 180 °C, with zinc chloride catalysis, to yield the styrylpyrazine (58), whereas the corresponding reaction of 2-methylpyrazine 1,4-dioxide proceeds at 25 °C under base catalysis (67KGS419). 

It has been discovered that direct chlorination of pyrazines can be accomplished and this has also been used to make candidate drugs. For example, when 2-methylpyrazine (120) is heated with chlorine in carbon tetrachloride, a mixture of the 3-chloro (121) and the 6-chloro derivatives result. After separation, 121 is heated with piperidine to give modaline (122), an antidepressant. 6... 

Scheme 21.—Formation of 2-Methylpyrazine from Saccharide Fragments.

Optically pure or almost pure a-methyl a-amino acids (alanine derivatives) can be prepared by reacting 5-substituted 2,5-dihydro-3,6-dimethoxy-2-methylpyrazines 1, which are derived from alanine and various amino acids as the chiral auxiliary, with alkylating agents, followed by hydrolysis (see Table 2). 

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). 

R,5R)-2-benzyl-5-(2-bromoethyl- -d2)-2,5-dihydro-3,6-dmethoxy-2-methylpyrazine yield 86% 56 % de... 

Figure 4. Profiles of volatiles for high-quality peanuts, raw and roasted (1) ethanol (2) pentane (3) 2-propanol (4) acetone (5) methylene chloride (6) methyl acetate (7) 2-methylpropanal (8) diacetyl (9) 3-methylbutanal (10) 2-methyl-butanal (11) 2,3-pentanedione (12) S-methylpyrrole (13) toluene (14) hexanal (15) 2-methylpyrazine (16) xylene (17) 2-heptanone (18) 2,5-dimethylpyrazine (19) 2-pentylfuran (20) 2-ethyl-5-methylpyrazine (21) 2-ethyl-3,6-dimethylpyra-zine (22) phenylacetaldehyde.

Pyrazines (see Sections II, V,B,2, and D). Both 2-amino- and 2-methylpyrazine react with Mel to give isomers. The observed isomer ratios are very close to those predicted by considering relative reactivities of the appropriately 2- and 3-substituted pyridines.62 The observation159 that 2-aminopyrazine undergoes quaternization... 

The pyrolysis of pyrazine at 1000°C/2mmHg gives pyrimidine in 3% yield (68TL3115). The photolysis of pyrazine at 254 nm gives a little pyrimidine in addition, 2-methylpyrazine gives both 4- and 5-methylpyrimidine, 2,6-dimethylpyrazine gives 4,5-dimethylpyrimidine, and 2,5-dimethylpyrazine gives both 4,6- and 2,5-dimethylpyrimidine, all in minute yield... 

The corresponding ylid from 2-methylpyrazine with DMAD in acetonitrile gave 4% of 264, and in refluxing chloroform, 8.5% of a 2 1 mixture (NMR) of adducts that were stated to be 264 and 265 on the presumption that the initial ylid was a single substance (263).329... 

Endo-trig cyclization of anion, formed from 2-methylpyrazine by LDA in THF at — 78 °C, with methyl 3-propynoate provided 6-methyl-8H-pyrido[l,2-f ]pyridazin-8-one in 52% yield (06TL5063). 

Acetyl-2-methylpyrazine (2 - Acetyl - 6- methy lpy razine) ch3 COCH... 

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... 

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