Methylpyrazines bromination

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). 

Conversion of pyrazinones into bromopyrazines is known (82MI2), as is side-chain bromination, particularly when NBS is used under conditions conducive to radical formation. Thus, 2-ethyl-3-methylpyrazine was converted into the l -bromoethyl derivative (72JOC511). 

Bromination of 23-diniethylpyrazine 1,4-dioxide in dioxane in the presence of benzoyl peroxide gave 2-(bromomethyl)-3-methyl- and 2,3-bis(bromomethyl)-pyrazine 1,4-dioxide (739), and 2-methylpyrazine 1,4-dioxide gave 2-bromo-... 

Ethoxyethyl)-5-hydroxy-2-methylpyrazine heated in acetic acid saturated with hydrogen bromide formed a crystalline bromine-containing compound which with 5% sodium carbonate gave 5-hydroxy-2-methyl-3-vinylpyrazine (248). Heteromacrocyclic ethers have been quaternized (989). 

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