Pyrazine, 2-acetyl

Acetylpyrazine gave its semicarbazone, 2-(l-semicarbazonoethyl)pyrazine (298) (H2NHNC0NH2.HC1, AcONa, EtOH—H20, 95°C, 15 min 90%)mo 2-[2-(Pyrazin-2-yl)acetyl]pyrazine (299) and 2-hydrazinopyrazine (300) gave 2-[2-(pyrazin-2-yl)-1 -(pyrazin-2-ylhydrazono)ethyl]pyrazine (301) (EtOH, reflux, 3 h %) 730 analogues likewise.730,731 Also other examples.283,866... 

Cyanopyrazine treated with a Grignard solution of methylmagnesium bromide in ether followed by treatment with dilute hydrochloric acid formed 2-acetyl-pyrazine (138). In a similar manner, 2-acetyl-5(and 6)-methylpyrazine (1327), 5-acetyl-2,3-diphenylpyrazine (866), and 2-acetyl-3,5,6-trimethylpyrazine (866) were prepared. 2-Cyanopyrazine with phenylma esium bromide has been reported to give 2-(C-imino-C-phenylmethyl)pyrazine (1220). 

Walradt et al ( ) investigated the postulated mechanism for the formation of acetyl and methyl acetyl pyrazines by Wange et al (10). Walradt proposed a mechanism for the formation of 6,7-dihdyro-5H oyolopentapyrazine as a result of the interaction of glyoxal and pyruvaldehyde with amino acids and 2-hydroxy-3-methyl-2-cyolopenten-l-one, a frequently occurring product of carbohydrate degradation. 

Acetyl propane. See Methyl isopropyl ketone Acetyl 2-propanone. See Acetylacetone Acetylpropionic acid 3-Acetylpropionic acid p-Acetylpropionic acid. See Levulinic acid Acetylpropionyl. See Pentane-2,3-dione Acetyl pyrazine. See 2-Acetyl pyrazine 2-Acetyl py razi ne... 

Synonyms Acetyl pyrazine Methyl pyrazinyl ketone Methyl 2-pyrazinyl ketone 1-Pyrazi nylethanone Pyrazi n-1 -ylethan-1 -one 1-Pyrazin-2-yl-ethanone... 

Pyrazine, 2,3-diethyl-. See 2,3-Diethylpyrazine Pyrazine hexahydride. See Piperazine Pyrazine, 2-methyl. See 2-Methylpyrazine 1-Pyrazinylethanone Pyrazin-1-ylethan-1-one 1-Pyrazin-2-yl-ethanone. See 2-Acetyl pyrazine 1H-Pyrazole-3-carboxylic acid, 4,5-dihydro-5-0X0-1 -(4-sulfophenyl)-4-[(4-sulfophenyl) azo]-, trisodium salt. See FD C Yellow No. 5 Tartrazine... 

Acetyl pyrazine 22047-49-0 Adeka Estol K-1201 Afilan EHS Cetiol 868 Crodamol OS Estol 1545 Estol EHS-b 3654 Exceparl EH-S HallStar OST Interwax G 8253 Lasemul 130 Lexol EHS Lexolube T-110 Octyl stearate Pelemol OS Rilanit EHS Sipoest 2EHS Sympatens-ES Tegosoft OS Unitolate 868 Wickenol 156 22104-80-9 2-Decenol... 

More than 100 different pyrazines have been identified in various food products. The sensory properties of the pyrazines are quite diverse. The alkyl pyrazines (Figure 5.5a) generally possess roasted, nut-like notes while methoxypyrazines (Figure 5.5b) often possess earthy, vegetable notes [47]. The 2-isobutyl-3-methoxy pyrazine has a freshly cut green pepper flavor with a sensory threshold of 0.002 ppb in water. The acetyl pyrazines typically have a popcorn character, and 2-acetonyl pyrazine has a... 

Direct oxidation of ethylpyrazines to the corresponding acetylpyrazines may also be carried out in favourable circumstances using hot chromic acid (75JOC1178). Treatment of 2-ethyl-3-alkylpyrazines with chromic acid yields the corresponding 2-acetyl-3-alkyl-pyrazines in yields of 50-70%. In the absence of the 3-alkyl substituent the yields fall dramatically to less than 10%. Acetylpyrazines are more generally prepared by the inverse addition of a Grignard reagent to a cyanopyrazine. 

A special influence on the course of a reaction by a neighboring group is shown in the reactions of 5-acetyl-leuco(iso)alloxazines - with diazomethane. The methylation occurs neither in the pyrimidine nor in the pyrazine ring, but on the hydroxyl group of a newly formed oxazoline ring. For example,... 

Acetyl-3-(perhydropyrido[l, 2-u]pyrazin-2-yl)-1 //-indole was deacety-lated in boiling MeOH in the presence of NaOH, and the product, 3-(perhydropyrido[l,2-u]pyrazin-2-yl)-l//-indole was N-acylated with different arylsulfonyl chloride in THF at 0°C in the presence of (Me3Si)2NNa (99MIP12, 01USP6251893)). 

Acylation of 3-arylamino-4-arylimino-4//-pyrido[l,2-u]pyrazines (373) with acyl chlorides afforded mixtures of mono- and bisacylated derivatives 374 and 375 (99JPR332). Acetyl chloride gave only monoacylated product 374 (R = 4-MePh, R =Me). Bis-acylated derivative 375 (R = 4-MePh, r = Me) was obtained in 68% yield in boiling toluene. Reaction of 373 with dienophiles 376 and 377 gave 4-thiono and 4-seleno derivatives of 4//-pyrido[l,2-u]pyrazines 378 (Y==S, Se) and 4-imino-4//-pyrido[l,2-u]pyrazines 379, respectively (99JPR332). 

Reaction of 3-(4-methylphenylamino)-4-(4-methylphenylimino)-4//-pyr-ido[l,2-a]pyrazine (373, R = 4-MePh) with ketenes 393, prepared in situ from the appropriate acetyl chloride with NEt3, yielded tricyclic derivatives... 

Cyclization of (25)-2-(rerc-butoxycarbonylaminomethyl)-l-(2-chloro-acetyl)piperidine on the action of NaH in THF gave (9aS)-2-(rerc-butoxycarbonyl)perhydropyrido[l,2-a]pyrazin-4-one (99H(51)2065). 3-Benzyl-2,3,4,4 ,5,6-hexahydro-l//-pyrazino[l,2-a]quinolin-l-ones 413... 

Substituted perhydropyrido[l,2-a]pyrazine-l,4-diones were obtained when methyl A-[2-(benzyloxycarbonylamino)acetyl]-4-substituted pipecoli-nates were hydrogenated over 10% Pd/C catalyst in MeOH, and then the methanolic solutions were refluxed (00JAP(K)00/86659). 

Zur reduzierenden Acetylierung von 3-Phenyl-bzw. 2,3-Diphenyl- pyrido-[2,3-b]-py-razin) in Acetonitril/Acetanhydrid zu 2-Phenyl-1,4-diacetyl-1,4-dihydro- (25% d.Th.) bzw. 2,3-Diphenyl-5-acetyl-5,8-dihydro-(pyrido[2,3-b]-pyrazin) (91% d.Th.) s. Lit.2 ... 

Condensation of phenylalaninenitrile, prepared from phenyl acetaldehyde, with 1-oxime of pyruvaldehyde afforded the pyrazine N-oxide, which was further rearranged to give the N-acetyl pyrazinone. The acetyl groups were removed by treatment with hydrazine to give the target 6-aminopyrazinone. 

Acylation of the piperazine nitrogen atoms of 47/,87/-bis[l,2,5]oxadiazolo[3,4- 4 -< ]pyrazine 59 with acetyl bromide proceeds smoothly in the presence of pyridine in acetonitrile to give 60 (Equation 9) <1997CHE618>. 

Pyrazine, 2-5-dimethyl Sd (roasted) ° Pyrazine, 2-6-dimethyl Sd (roasted) ° Pyrazine, 2-acetyl Sd Pyrazine, 2-ethyl-3-5-6-methyl Sd (roasted) ° ... 

Pyrazine, 2-ethyl-3-methyl Sd (roasted) ° Pyrazine, 2-ethyl-5-methyl Sd (roasted) ° Pyrazine, 2-ethyl-6-methyl Sd (roasted) ° Pyrazine, 3-5-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-5-dimethyl-2-acetyl Sd Pyrazine, 3-6-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-6-dimethyl-2-acetyl Sd Pyrazine, 3-ethyl-2-5-dimethyl Sd (roasted) " ... 

Pyrazine, 3-methyl-2-acetyl Sd Pyrazine, 5-6-dimethyl-2-(2 -furyl) Sd... 

---