2-Butyl-6-methylpyrazine

V-Butyl-/V -methyl-3,5-bismethylamino-2,6-pyrazinedicarboxamide N-tert-Butyl-N -methyl-3,5-bismethylamino-2,6-pyrazi nedicarboxamide 2-Butyl-3-methylpyrazine... 

Alkyl-2-methoxypyrazines exhibit a base peak at miz 124 in the mass spectrum. The peak corresponds to a molecular ion in 2-methoxy-3-methylpyrazine (24a) and to a fragment ion, resulting from a McLafferty rearrangement of an alkyl group, in 3-isopropyl-2-methoxypyrazine (24b) and 3-5cc-butyl-2-methoxy pyrazine (24d) (97). 

S c- Buty 1-5 - methylpyrazine 2-Butyl-6-methylpyrazine 2-5, c-Butyl-6-methylpyrazine 2-te rt- B utyl - 6- methylpyrazine 2-s c- Buty 1-5 - methylpyrazine 4-oxide 6-s c-Butyl-3-methyl-2(l /)-pyrazinone Butyl 6-oxo-l,6-dihydro-2-pyrazinecarboxylate 4-oxide 2-Butyl-3-pivalamidopyrazine 2-sec-Butyl-3-pivalamidopyrazine... 

Recent work has shown the presence of pyrazine and 2,6-dimethylpyrazine in leek (75), pyrazine and alkylpyrazines in the volatile constituents of tamarind (76), five alkylpyrazines in soong-neung (extract of cooked and roasted rice) (77) and in shoyu (soy sauce) (78), and alkylpyrazines in white bread (79). Murray and Whitfield (80) have examined vegetable tissue for 2-isopropyl-, 2is-butyl-, and 2-isobutyl-3-methoxypyrazines and observed at least one of these compounds in 23 of the 27 samples studied. 2-Methylpyrazine and 2,5- and 2,6-dimethylpyrazines have been determined in black tobacco and in the smoke of nonfilter cigarettes made from these tobaccos (81). 

Ring aUylation and propenylation of methylpyrazine has been described (634) acetonylpyrazine with phenyllithium gives 2-acetonyl-6-phenylpyrazine (639) and 2,5-dimethylpyrazine with isopentylUthium gave 3-isopentyl-2,S-dimethylpyrazine (70). Aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia, or a suspension of these metals in other solvents, can be used to alkylate the pyrazine ring in moderate to good yields (614, 640, 641). This alkylation has been successfully applied to alkyl- and dialkyl(amino- and methoxy)pyrazines, and a mechanism has been proposed for the reaction (614). For example, the reaction of potassium with methylpyrazine and ethyl methyl ketone, catalyzed by sodamide (0.25 mol) gave 88% of 2 -butyl-6-methylpyrazine. 

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). 

Chloro-3-methylpyrazine (101,535) and 2-chloro-5-phenylpyrazine (363, 365a, 377, 824, 825) have been prepared from the corresponding hydroxy compound and phosphoryl chloride, 2-chloro-6-methylpyrazine from 2-hydroxy-6-methylpyrazine and phosphoryl chloride with one drop of dimethylformamide (681), and 2-benzyl(or s-butyl, isobutyl, or isopropyl)-3phosphoryl chloride with a trace of concentrated sulfuric acid (80). 2-Chloro-6-methyl-3-propyl- (826), 3[Pg.99]

Alkylations of halogenopyrazines have been effected as follows tetrafluoro-pyrazine with ethereal methyllithium at — 70° gave 2,3,5-trifluoro-6-methylpyrazine (851, 965), and with butyllithium in ether-hexane gave 2-butyl-3,5,6-trifluoro-, 2,5-dibutyl-3,6-difluoro-, and 2,3,5-tributyl-6-fluoropyrazines (851) tetrachloro-... 

Klein et al. (978) first attempted the alkaline hydrolysis of 3-chloropyrazine 1 -oxide to 3-hydroxypyrazine 1 -oxide, and although spectroscopic evidence indicated the formation of the hydroxy compound, good quality homogeneous material could not be isolated. Later work by Berkowitz and Bardos (1034) has shown that 3-chloropyrazine 1-oxide was hydrolyzed by refluxing with two equivalents of aqueous sodium hydroxide, and treatment of the product with trimethylsilyl chloride and triethylamine gave 3-(trimethylsilyl)oxypyrazine 1-oxide. 3,6-Di-s-butyl-2-hydroxypyrazine 1-oxide has been prepared from the chloro analogue (no details given) (982). Hydrolysis of 2-amino-6-chloro-3-cyano-5-methylpyrazine... 

Diazotization of 2-aminopyrazine with nitrous acid in dilute or concentrated sulfuric acid gave 2 hydroxypyrazine (to 67% yield) (86, 477, 720, 818). Many such conversions have been described, mostly using nitrosylsulfuric acid in concentrated sulfuric acid solution. Preparations of hydroxypyrazines from the aminopyrazines are summarized as follows 2-hydroxy-3-methylpyrazine (sodium nitrite in concentrated sulfuric acid-acetic acid) (681), 2Jiydroxy-3,5-dimethylpyrazine (aqueous nitrous acid, then at 60°) (524), 3-hydroxy-2,5-dimethylpyrazine (477), 2,5-diethyl-3-hydroxypyrazine (aqueous nitrous acid) (478), 2-hydroxy-6-phenyl-pyrazine (365a), 24iydroxy-3,5-diphenylpyrazine (nitrous acid in N hydrochloric acid) (524), 3-hydroxy-2,5-diphenylpyrazine (282), 2-s-butyl-3-hydroxy-5-isobutyl-pyrazine (93), 5TS-butyl-3 hydroxy-2-isobutylpyrazine (92, 536), 2,5-di-s-butyl-3-hydroxypyrazine (89, 720), 3-hydroxy-2-isobutyl-5-isopropylpyrazine (103, 525), 2,3-dihydroxypyrazine (from 2 amino-3-hydroxypyrazine) (757, 1055) and its... 

In 23-dihydroxypyrazine and derivatives Honzl (853), from measurements of infrared spectra in chloroform and ultraviolet spectra in aqueous alcohol, has proposed that 5,6-dichloro-l-cyclohexyl-3-hydroxy-2-oxo-l, 2-dihydropyrazine (pA in water 4.66, 5.66) exists in the form (48). The p.m.r. spectra of some 5- and 6-methyl- and 5- and 6-phenyl-2,3-dihydroxypyrazines have been reported (483). In the 2,5-dihydroxypyrazine series, the infrared spectrum (Nujol) of 2-benzyl-3,6-dihydroxy-5-methylpyrazine has been interpreted as indicating that the major tautomeric form present in the solid state was the dihydroxy form (49), but the ultraviolet spectrum in ethanol was considered consistent with the coexistence of the dihydroxy (49) and oxo-hydroxy form, for example, (50), Although the structure (51) has been proposed for 3-butyl-2,5-dihydroxypyrazine (1092), the evidence in favor of this structure is inconclusive. 

Methylpyrazine added to sodium amide in liquid ammonia and treated with butyl nitrite gave 2-hydroxyiminomethylpyrazine (727, 728) and 2,3,5-trimethyl-6-pentylpyrazine similarly treated gave 2-hydroxyiminomethyl-3,6-dimethyl-5-pentylpyrazine (648). 

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