2-Isobutyl-5-methylpyrazine

Ethylenediamine (168) and 5-methyl-3-phenylimino-2-hexanone (169) (liberated in situ) gave 2-isobutyl-3-methylpyrazine (170) (Me NCHO, 80°C, 24 h then NaOH/MeOH, 02 J, 60°C, 3 h >64%).753-754... 

In a similar manner, 3-isobutyl-6-methyl-3,6-dihydro-2,5(l//,4//)-pyrazinedione (9, R = Me) gave 2-chloro-3-isobutyl-6-methylpyrazine (10, R = Me), 2-chloro-6-isobutyl-3-methylpyrazine (11, R = Me), and 2,5-dichloro-3-isobutyl-6-methylpyrazine (12, R = Me) (27, 21, and 4%, respectively).295... 

Chloro-5,6-diethylpyrazine 1-oxide (219) (K2S2Os, H2S04, 20°C, 24 h 84%) 1250 2-chloro-3-isobutyl-6-methylpyrazine 1-oxide (220) (likewise 78%) 295 and 2-fluoropyrazine 1-oxide (likewise 40%).276... 

Isobutyl-5-methylpyrazine from its 4-oxide (248) (neat PC13, 100°C, sealed, 30 min 56%) 295 homologues likewise.298... 

Acetoxymethyl- -chloropyrazine 2-Acetoxymethyl-3,6-dichloro-5-methylpyrazine 2-Acetoxymethyl-3,6-dichloro-5-methylpyrazine 1-oxide 2-Acetoxymethyl-3-ethoxypyrazine 2-Acetoxymethyl-5-isobutyl-3-methoxypyrazine 2-Acetoxymethyl-5-isobutyl-3-methoxypyrazine 1-oxide 2-Acetoxymethyl-3-methoxy-5-methylpyrazine 2-Acetoxymethyl-5-methoxy-6-methylpyrazine 2-Acetoxymethyl-3-methoxy-5-methylpyrazine 1-oxide 2-Acetoxymethyl-3-methylpyrazine 2-Acetoxymethyl-5-methylpyrazine... 

Chloro-3-isobutyl-6-isopropylpyrazine 1 -oxide 2-Chloro-3-isobutyl-6-isopropylpyrazine 4-oxide 2-Chloro-6-isobutyl-3-isopropylpyrazine 4-oxide 2-Chloro-3-isobutyl-6-methylpyrazine 2-Chloro-6-isobutyl-3-methylpyrazine 2-Chloro-3-isobutyl-6-methylpyrazine... 

Isobutyl-3-methoxy-5-methylpyrazine 2-Isobutyl-3-methoxy-5-methylpyrazine 2-Isobutyl-6-methoxy-5-methylpyrazine 4-oxide 2-Isobutyl-3-methoxypyrazine... 

Isobutyl-5-methylpyrazine 2-IsobutyT6-methylpyrazine 2-Isobutyl-5-methylpyrazine 1-oxide... 

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). 

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]

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... 

Methoxypyrazines (31) have been prepared by diazomethane methylation of 2-hydroxy-3-isobutylpyrazine (60, 311, 367), 2-hydroxy-3-isopropylpyrazine (59, 367), 2-hydroxy-3-propyl(ethyl or hexyl)pyrazine (367), 3-hydroxy-2-isobutyl-5(and 6)methylpyrazine and 2-hydroxy-3-isobutyl-5,6-dimethylpyrazine (368), 2,3-dihydroxypyrazine (832), 2-hydroxy-5-methoxy- and 2,5-dihydroxy-3,6-diphenyl-pyrazine (832), 2-hydroxy-6-methoxy(and benzyloxy)pyrazine (832), 2,6-dihydroxy-3,5-diphenylpyrazine (873), 2,3,5-trifluoro-6-hydroxypyrazine (851), 2-chloro-6-hydroxy-3,5-diphenylpyrazine (873), 2-chloro-6-hydroxy-5-methyl-3-phenylpyrazine (873), 2-chloro-6-hydroxy-3-methyl-5-phenylpyrazine (873), 5,6-dichloro-1 -cyclohexyl-34iydroxy-2-oxo-l, 2-dihydropyrazine (853), 2-chloro-5-hydroxy-3-methoxy-6-methoxycarbonylpyrazine (881), 2-(4 -amino-3, 5 -dibromo-phenylsulfonamido)-3Tiydroxy-6-methoxypyrazine (881), 2-amino-3-hydroxy-... 

A large number of 2-alkyl-3-methoxypyrazines has been isolated from raw vegetables (59, 60, 64, 65, 69, 80, 1099), bell peppers (60,61) and gambanum oil (49). 2-Isobutyl-3-methoxypyrazine is already finding commercial use as a flavoring material (368) and 2-ethoxy-3-methylpyrazine may be used for pineapple flavor (981). The odor characteristics (367, 368, 976, 977) and structure (977) of some alkoxy alkylpyrazines have been examined. 3-Guanidino-6-hydroxymethyl-l-methyl-2-oxo-l,2-dihydropyrazine has been isolated from seeds of Stizolobium hassjoo and on mild alkaline hydrolysis gave 3-hydroxy-6-hydroxymethyl-l -methyl-2-oxo-l, 2-dihydropyrazine (1060). 

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