2-Hydroxy-5-methoxycarbonyl-3,6-dimethylpyrazine

Irradiation of 2,5-bis(methoxycarbonyl)-3,6-dimethylpyrazine in diethyl ether with a 450-W high-pressure mercury lamp (330 nm) gave two significant photoproducts 2-hydroxy-5-methoxycarbonyl-3,6-dimethylpyrazine and l-(l -ethoxy-ethyl)2,5-dimethoxycarbonyl-3,6-dimethyl-l, 4-dihydropyrazine (74). Similar products were isolated when tetrahydrofuran was used as solvent. Corresponding reactions were observed with 2,5-bis(ethoxycarbonyl)-3,6-dimethylpyrazine, 2,5-diacetyl-3,6-dimethylpyrazine, and 2,5-dibenzoyl-3,6-dimethylpyrazine. The mechanism of these reactions were investigated and the initial stage was found to be... 

Hydrogenation of 4-hydroxy-3-methoxycarbonyl-6-oxo-l, 2(6/f)-oxazine (122) in methanol over palladium-charcoal has been shown to give 2,5-dimethoxy-carbonyl-3,6-dimethylpyrazine (501) and 3-amino-4-hydroxycoumarin (123, R = r2 = H), 3-amino4-hydroxy-6,8-dimethylcoumarin and 3-acetamido-4-hydroxy-6-methylcoumarin, when heated vrith 2N sodium hydroxide, gave... 

Dicyano-3,6-dimethylpyrazine shaken with sodium ethoxide at room temperature for 10 hours produced 2-cyano-5-ethoxy-3,6-dimethylpyrazine (288). Bromination of 2-methoxy-3-sulfanilamidopyrazine (39) in methanol led to 5-(4 -amino-3, 5 -dibromobenzenesulfonimido)-6-hydroxy-2,3-dimethoxy-2,3,4,5-tetrahydropyrazine (32) which with 2 N sodium hydroxide gave 3-(4 -amino-3, 5 -dibromobenzenesulfonamido)-2-hydroxy-5 nethoxypyrazine (40) (816). The preparation of 2-amino-3,5-dicyano-6-methoxy(and ethoxy)pyrazine from a-(p-toluenesulfonyloxyiminomalononitrile and malononitrile has been described in Section II.7 (484). 2-Methoxycarbonyl(and cyano)-5-pyridiniopyrazine chloride (41) is reported (conditions not stated) to give 2-carboxy(and carbamoyl)-5-methoxypyrazine (765). 

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