2.5- Diethoxy-3,6-dimethylpyrazine

Dichloro-3,6-dimethylpyrazine 1,4-dioxide (91) with sodium methoxide at room temperature gave 2,5-dimethoxy-3,6-dimethylpyrazine 1,4-dioxide (92) and a trace of 2-hydroxy-5-methoxy-3,6-dimethylpyrazine 1,4-dioxide (93) (756). Similarly 2,5-dichloro-3,6-dimethylpyrazine 1,4-dioxide (a) with sodium ethoxide gave 2,5-diethoxy-3,6-dimethylpyrazine 1,4-dioxide (756, 842) and 2-hydroxy-5-... 

Diniethylpiperazine-2,5-dione (34) on treatment with triethyloxonium fluoroborate in dichloromethane gave 5-ethoxy-l,3-dimethyl-2-oxo-l, 2,3.6-tetrahydropyrazine which was oxidized by DDQ in dry benzene to 5-ethoxy-l 3 dimethyl-2-oxo-l,2-dihydropyrazine (35) (1067). l,3,6-Trimethylpiperazine-2,5-dione similarly treated gave three products, one of which was assigned the structure 5-methoxy-l 3,6-trimethyl-2-oxo-l, 2-dihydropyrazine 3-benzyl-5-methoxy-l, 6-dimethyl-2-0X0-1,2-dihydropyrazine was also prepared similarly (1078). When 3,6-diethoxy-2,5"dimethyl-2,5-dihydropyrazine was refluxed with lead tetraacetate in dry benzene it gave a mixture of 2,5-diacetoxy-3,6-diethoxy-2,5-dimethyl-2,5-dihydropyrazine (36) (4 parts) and 2,5-diethoxy-3,6-dimethylpyrazine (1 part) (1068). 

Alkoxypyrazine A -oxides may be hydrolyzed with acid to hydroxypyrazine A -oxides. Some examples are the hydrolysis of 3-ethoxy-2,5-dimethylpyrazine 1-oxide at reflux with 3 A hydrochloric acid to give 3-hydroxy-2,5-dimethylpyrazine 1-oxide (872) 2,5-diethoxy-3,6-dimethylpyrazine 1,4-dioxide with 2N hydrochloric acid at 70° gave 2-ethoxy-5-hydroxy-3,6-dimethylpyrazine 1,4-dioxide and 2,5-dibenzyloxy-3,6-dimethylpyrazine 1,4-dioxide similarly treated but at room temperature gave the 2-benzyloxy analogue (842), but with lOAf hydrochloric acid at room temperature it gave 2,5-dihydroxy-3,6-dimethylpyrazine 1,4-dioxide (842). 

Diethoxy-3,6-dimethylpyrazine similarly gave 3,6-diethoxy-2,5-dimethyl-2,5-epidioxy-2,5-dihydropyrazine, which was reduced by sodium borohydride to 3,6-diethoxy-2,5-dihydroxy-2,5-dimethyl-2,5-dihydropyrazine (1127). 

Oxidation of 2,5-diethoxy-3,6-dihydropyrazine with dichlorodicyanobenzo-quinone (DDQ) formed 2,5-diethoxypyrazine (314), and the 3,6-dimethyl analogue reacted similarly (314). 2,5-Diisopropyl-3,6-dimethyl-2,5-dihydropyrazine was oxidized in alkaUne solution to 2,5-diisopropyl-3,6-dimethylpyrazine (225). Oxidation of 2,5-diethoxy-3,6-dimethyl-3,6-dihydropyrazine with lead tetraacetate in refluxing benzene gave both 2,5-diethoxy-3,6-dimethylpyrazine (minor product) and 2,5-diacetoxy-3,6-diethoxy-2,5-dimethyl-2,5-dihydropyrazine (1068). 

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-... 

Reduction of pyrazine with potassium in 1,2-diethoxy ethane at — 70° gives the paramagnetic radical anion. Anions have also been generated from the low-temperature reaction of pyrazine, methyl-pyrazine, 2,5- and 2,6-dimethylpyrazines with sodium or potassium in tetrahydrofuran or 1,2-dimethoxyethane. From measurements of their ESR spectra, ion-pair formation is proposed between the alkali metal cation and the pyrazine anion.96-101... 

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