3- Ethoxy pyrazine 1-oxide

Pyrazin 5-Amino-6-cyan-3-ethoxy-carbonyl-2-methyl- E9b/2, 311 f. (N-Oxid-Red.)... 

Pyrazin-l,4-bis-oxid 2,5-Dimethyl-3-pentyl-E9b/2, 305 (N-Bis-oxidat.) lH-Pyrazol l-tert.-Butyl-4-ethoxy-carbonyl-5-methyl- E8b, 461 [R2N - CH = C(COOR) - CO -CH3R-NH-NH2]... 

Dimethoxy(or diethoxy)-3,6-dimethylpyrazine 1,4-dioxide with phosphoryl chloride have been shown to give 2,5-bis(chloromethyl)-3,6-dimethoxy(or diethoxy)-pyrazine (756), 3-ethoxy-2,5-dimethylpyrazine 1-oxide gave 2-chloro-5-ethoxy-... 

Ethoxypyrazine 1-oxide refluxed with 40% alcoholic hydrogen chloride yielded 2-ethoxy-5-hydroxypyrazine (1069). Ultraviolet irradiation of 2,5-dimethyl-pyrazine 1-oxide in water afforded 3-hydroxy-2,5-dimethylpyrazine (10%) and 2,5-diphenylpyrazine 1-oxide in benzene gave 3-hydroxy-2,5-diphenylpyrazine (3%) (742). A small yield of 2-ethyI-5-hydroxy-3,6-dimethylpyrazine has been isolated as by-product from the reaction of 2,5-dimethylpyrazine with ethyllithium in ether (615). 

Alkoxypyrazine A-oxides may also be prepared by oxidation of the alkoxypyrazine with peroxyacetic acid. In this way the following have been prepared 3-ethoxypyrazine 1-oxide (100°/20h) (978) 3-(trideuteromethoxy)pyrazine 1-oxide (757l9h) (975) 3-ethoxy-2-methylpyrazine 1-oxide (65-75724h) (978) 3-methoxy-2-phenylpyrazine 1-oxide (55720 h) (817) 3-ethoxy-2,5-dimethyl-pyrazine 1-oxide (56716 h) (872) 3-carbamoyl-2-methoxypyrazine 1-oxide (80720h) (881) and 2-cyano-5-ethoxy-3,6-dimethylpyrazine A-oxide (55720h) (288). 

Reactions of C-alkoxypyrazine A-oxides with phosphoryl chloride have been described in Section V.IG (756, 817, 838, 872, 881). For example, 3-ethoxy-2,5-dimethylpyrazine 1-oxide refluxed with phosphoryl chloride for 10 minutes gave 2-chloro-5-ethoxy-3,6-dimethylpyrazine and 2-chloromethyl-3-ethoxy-5-methyl-pyrazine (872). 

Alkoxycarbonylpyrazines have been oxidized to alkoxycarbonylpyrazine Af-oxides as follows 2-ethoxycarbonylpyrazine with perhydrol gave 3-ethoxy-carbonylpyrazine 1-oxide (575) 2-amino-3-methoxycarbonylpyrazine refluxed with m-chloroperoxybenzoic acid in chloroform gave 2-amino-3-methoxycarbonyl-pyrazine 1-oxide (876,880,1222) the 5-bromo (808, 877,878, 1222) and 5-chloro (875, 876, 879, 1222) derivatives were prepared similarly and some 3-ethoxy-carbonylpyrazine 1-oxides have been prepared by oxidation (reagent not stated) of... 

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