5- Hydroxy-3-methyl-2- pyrazine, reduction

Pyrolyses and thermal stabilities of 2-hydroxy-, 2-ethoxy-, and 2-isopropoxy-pyrazines have been studied. 2-Hydroxypyrazine was very stable, but the alkoxy-pyrazines underwent thermal elimination of olefin to yield 2-hydroxypyrazine (668a). Electrochemical reductions of l-methyl-2-oxo-5,6-diphenyl-l,2-dihydro-pyrazine and 54iydroxy(and 5-methoxy)-2,3-diphenylpyrazine are reported to involve the intermediate enamine, for example, 6-hydroxy-1-methyl-2,3-diphenyl-1,4-dihydropyrazine (54) (1096, cf. 1097). When tested on mice 2-carbamoyl-5-methoxypyrazine had less anti tubercular activity than did pyrazinamide (1098). 

Reductions of a series of pyrazine A -oxides with sodium borohydride in water or methanol at room temperature gave A -hydroxypiperazines for example, 2,3,4-trimethylpyrazinium 1-oxide iodide gave 1-hydroxy-2,3,4-trimethylpiperazine (766). When tosylated diethanolamine was allowed to react with hydroxylamine, detosylation and methylation occurred to afford l-hydroxy-4-methylpiperazine (1673). 

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