1.2.3- Trimethylpyrazinium iodide

Trimethylpyrazinium iodide in liquid ammonia adds at the 6-position to form the 6-adduct (22) (609) nitromethide and ethanethiolate ions at — 60° add to the 6-position of 1,2,5-trimethylpyrazinium ion to give adducts (23, X = CHNO and SCH3), respectively (721). 

Dimethyi-l-phenacylpyrazinium bromide (from 2,5-dimethylpyrazine and phenacyl bromide) and dimethyl acetylenedicarboxylate has been shown to give 6-benzoyl-7,8-bis(methoxycarbonyl)-1,4-dimethylpyrroIo[ 1,2-a] pyrazine (25) and 7,8-bis(methoxycarbonyl)-l,4-dimethylpyrrolo[l,2-fl]pyrazine (26) (723), and 1,2,5-trimethylpyrazinium iodide and dimethyl acetylenedicarboxylate also gave a 1% yield of (26). Addition reactions of 2-methyl- (724), 2,6-dimethyl- (724), 2,5-dimethyl- (725), and 2,3,5,6-tetramethylpyrazine (725), with dimethyl acetylenedicarboxylate have also been investigated. 

Methylpyrazine is methylated with methyl iodide in dimethyl sulfoxide at room temperature to give l-methyl-3-methylpyrazinium iodide and i-methyl-2-methyl-pyrazinium iodide, in a ratio of 3.9 I. The rate of methylation relative to pyrazine was 2.06 (666). The reaction of 2,5-dimethylpyrazine with iodo- or bromoacetic acid to give the 1,2,5-trimethylpyrazinium salt has been investigated (3). A kinetic study of the reaction of sodium hydroxide on quaternary pyrazinium salts (667, 668) has been made using a conductivity method to follow the progress of the reaction (11=5 12). In the case of 1,2,5-trimethylpyrazinium hydroxide, equilibrium lies toward (11), which slowly disappears, presumably forming the ether (13) (668). When 1,2,5-trimethylpyrazinium bromide was heated in a sealed tube trimethyl- and tetramethylpyrazine were produced (660). 

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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