2-Acetyl-3-methylpyrazine

Bromination using NBS has been used to provide acetylpyrazine derivatives from the corresponding ethylpyrazines. Bromination of 2-ethyl-3-methylpyrazine gives 2-bromoethyl-3-methylpyrazine in quantitative yield this may be oxidized using the sodium salt of 2-nitropropane or with pyridine AT-oxide to yield 2-acetyl-3-methylpyrazine in yields of 66 and 25% respectively (Scheme 14). 

Some 2 -dialkylpyrazines have been oxidized in one step with sodium dichromate in acetic acid, in good yields, to the corresponding 2-acyl-3-alkylpyrazines (678). Thus 2-ethyl-3-methylpyrazine gave 2-acetyl-3-methylpyrazine, 23-diethylpyrazine gave 2-acetyl-3-ethylpyrazine, and 2-ethyl-3,5(or 3,6)-dimethylpyrazine gave 2-acetyl-3,5(or 3,6)-dimethylpyrazine (678). 

Linalool ( ,Z)-2,6-Nonadienal 2- Acet dpyrazine 2-Acetyl-3-methylpyrazine... 

Ethanone, l-(3-methylpyrazinyl)-, l-(3-methylpyrazin-2-yl)ethanone, 2-acetyl-3-methylpyrazine [23787-80-6]... 

Ethanone, 1-(3-methylpyrazinyl)- 2-acetyl-3-methylpyrazine 1587a, 4249,4570a 937, 2337, 3219, 3491, 3547, 3974a, 4249 ... 

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

Dimethoxy-3-acetyl- -6-methylpyrazine och3 coch3 och3 X u... 

The irans-benzylidene derivative (188), obtained as the major product of condensation of 3-methylpiperazine 2,5-dione and benzaldehyde in the presence of acetic anhydride, undergoes photoisomerization to the cis isomer (191) on irradiation in methanol. Both isomers have been converted into tetrahydropyrazine imino ethers (189) and (192) by treatment with triethyloxonium fluoroborate. The trans compound reacts more slowly and gives a lower yield of imino ether and this is attributed to steric hindrance. Compounds 188 and 191 are de-acetylated on treatment with methanolic 2 N potassium hydroxide. The trans and cis isomers (187) and (190), so produced are converted into 3-benzyl-2,5-dihydroxy-6-methylpyrazine (144) when heated at 100° with sodium hydroxide.384 Treatment of the dichloroacetyl derivative of phenylalanine with methylamine gives l-methyl-3-benzylidenepiperazine 2,5-dione with the stereochemistry shown.384a... 

Tomato (fresh) Solanum 2-acetyl-1 -pyrroline, dimethyl trisulfide, 2,3-diethyl-5-methylpyrazine (Z)-3-Hexenal, hexenal, 1 -octen-3-one, methional 131,169... 

Benzoyloxypyrazine and 2-benzoyloxy-6-bromopyrazine were each prepared from the hydroxypyrazine with benzoyl chloride in anhydrous pyridine (865) but it has been reported that 3-hydroxy-2,5-diphenylpyrazine could not be acetylated (317), and 2-hydroxy-6-methylpyrazine could not be acetylated or benzoylated in pyridine solution (434). 

The Vilsmeier reaction on 2-methylpyrazine has been described in Section IV.2C(7) (717), and King s reaction on 2-methyl(and 23-dimethyl)pyrazine 1,4-dioxide has been described in Section IV.3C(7) (763). Pyrazine with A, jV-dimethyl-acetamide, ammonium peroxydisulfate, and ferrous sulfate gave 2-(A -acetyl-iV-methylaminomethyl)pyrazine (1188). 

Aminopyrazine jV-oxides may rearrange and acetylate in the presence of acetic anhydride. Thus 2-amino-3with acetic anhydride and acetic acid at reflux for 2 hours gave 3.acetamido-2-carbamoyl-5-hydroxypyrazine (25), 2-amino-3[Pg.216]

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). 

Chlorocarbonyl-2-methoxy-5-methylpyrazine with lithium dimethyl copper reagent in ether gave 3-acetyl-2-methoxy-5-methylpyrazine 2-acetyl-3-methoxy-pyrazine and 2-acetyl-3,6-dimethoxy-5-methylpyrazine were prepared similarly (844), but 2-chlorocarbonyl-3-methoxy-5-methylpyrazine with lithium dimethyl copper in ether gave a mixture of 2-acetyl-3-methoxy-5-methylpyrazine and 2-(l-hydroxy-1-methylethyl)-3-methoxy-5-methylpyrazine (844). 

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