2-Methoxypyrazine 1,4-dioxide

The following pA values have been measured 3-methoxypyrazine 1-oxide, — 0.45 (745) aspergillic acid, 5.5 (94) and hydroxyaspergillic acid, 4.9 (94). P.m.r. measurements have shown that 2-methoxypyrazine 1,4-dioxide protonates at N-4 (1136). 

Chloro-3,6-difluoro-5-hydrazinopyrazine 2-Chloro-3,6-difluoro-5-methoxypyrazine 2-Chloro-3,6-diisobutyl-5-methoxypyrazine 2-Chloro-3,6-diisobutylpyrazine 2-Chloro-3,6-diisobutylpyrazine 1, 4-dioxide... 

Guanidinopropyl)-3-isopropyl-2(l//)-pyrazinone 3,6,AA V,X-Hexamethyl-2,5-pyrazinedicarboxamide 2-Hexylamino-3,6-dimethylpyrazine 2-Hexylamino-3,6-dimethylpyrazine 4-oxide 2-Hexylaminopyrazine 2-Hexylaminopyrazine 4-oxide 2- Hexyl- 3,6-dimethylpyrazine 2- Hexyl- 5,6- dimethy lpy razi ne 2- Hexyl -3,6- dimethy lpy razi ne 1,4- dioxide 2-Hexyl-3-methoxypyrazine 2- Hexyl- 3-methylpyrazine... 

Diisobutyl-3-methoxypyrazine 1,4-dioxide with phosphorus trichloride in ethyl acetate at 40° gave 2,5-diisobutyl-3-methoxypyrazine (and 2,5-diisobutyl-4-methoxy-3-oxo-3,4-dihydropyrazine 1-oxide similarly treated gave 3,6-diisobutyl-I-methoxy-2-oxo-l, 2-dihydropyrazine) (see Section 15) (980). 

Cleavage of the Me-0 bond in 3,6-diisobutyl-l-methoxy-2-oxo-l,2-dihydro-pyrazine (93) with methylmagnesium iodide at 150° gave 2-hydroxy-3,6-diisobutyl-pyrazine 1-oxide (94) and the 1,4-dioxide was prepared similarly from 2,5-diisobutyl4-methoxy-3-oxo-3,4-dihydropyrazine 1-oxide and also from 2,5-diisobutyl-3-methoxypyrazine 1,4-dioxide (980). 

Diazomethane methylation of 3-hydroxy-2,5-diisobutylpyrazine 1,4-dioxide has been shown to give the 4-methoxypyrazine 1-oxide, 2,5-diisobutyl4-methoxy-3-0X0-3,4-dihydropyrazine 1-oxide (96) (843, 980) [and some 3-methoxy-2,5-diisobutylpyrazine 1,4-dioxide (4 l)(980)] 5-s-butyl-3-hydroxy-2-isobutylpyrazine... 

Unlike pyridine A-oxides where electrophilic substitution is facilitated by the electron-donating effect of the A-oxide oxygen, pyrazine A-oxides are inert to this substitution. For example, 2,5-dimethylpyrazine 1,4-dioxide could not be nitrated with sodium nitrate in sulfuric acid at 70°C and 75% of the dioxide was recovered after 16 hours <58JOC1603>. However, 3-methoxypyrazine 1-oxide... 

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