2.5 -Diethoxy-3 - pyrazine

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-... 

Diethoxy-3-(l-hydroxy-l-methylethyl)pyrazine (155) gave 2,5-diethoxy-3-isopropenylpyrazine (156) (TsOH, PhH, molecular sieves, reflux 80%) 6 2-(l-hydroxy-2-methylpropyl)-6-iodo-3-methoxypyrazine gave 2-iodo-5-methoxy-6-(2-methylprop-l-enyl)pyrazine (157) (TsOH, PhMe, reflux with H20 removal, 6 h 65%).1588... 

Pyrazin 2,5-Diethoxy- E9b/2, 295 ( — H2 -> Hetaren) Pyrazin-l,4-bis-oxid Tetramethyl-E9b/2, 305 (N-Bis-oxidation) Pyrazin-l-oxid 3,6-Diethyl-2-hydroxy- E9b/2, 312 (4-Oxid-Red.)... 

Furan 2-Aminomethyl-5-(2,4-dioxo-1,2,3,4-tetrahydro-pyrimidino)-2,5-dihydro- IV/lc, 578 Imidazo(l,2-a]pyridin 1,5-Dimethyl-8-nitro-7-oxo-l,2,3,7-tetrahydro-E15/3, 2790 [cycl. (R2N)2C = CH-N02 4- Diketen] 1,3-Oxazol 4-Cyan-5-(diethoxy-methylen-amino)- E4, 565 (Het — NH2 + Orthoester) Pyrazin 3-Amino-2-methoxycarbo-nyl-5-propanoyl- E9b/2, 324 (H - CO-R)... 

A series of methoxy compounds have been prepared from 2-hydroxy-3-(a-hydroxybenzyl)pyrazines and dimethyl sulfate (1045), and 2-benzyl-3,6-dihydroxy-pyrazine with diethyl sulfate and sodium ethoxide gave the 3,6-diethoxy derivative (1066). 

Methylation of 2-hydroxy-3-7V-phenylcarbamoylpyrazine with dimethyl sulfate and potassium carbonate in boiling acetone gave l-methyl-2-oxo-3-A -phenylcarbamoyl-1,2-dihydropyrazine and the 3-(A -methyl-Af-phenylcarbamoyl) analogue was prepared likewise (1055). Similar methylation of 2-hydroxy-3-(o-methylaminophenyl)pyrazine produced 1 -methyl-3-(o-methylaminophenyl)-2-oxo-1,2-dihydropyrazine (1055). A series of 24iydroxy-3-(a-hydroxybenzyl)pyrazines has been methylated with dimethyl sulfate in aqueous sodium hydroxide to the 2-methoxy analogues (1045) and 2-benzyl-3,6-dihydroxy-5-methylpyrazine with diethyl sulfate and sodium ethoxide formed 2-benzyl-3,6-diethoxy-6-methylpyrazine (1066). 

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... 

The reaction of 2,3-dichloropyrido[2,3-0]pyrazine (9) with ethanolic potassium hydroxide is reported to give 3-ethoxypyrido[2,3-( ]pyrazin-2(1 H)-one (10), whereas by the same treatment 2,3,7-trichloropyrido[2,3-0]pyrazine is converted into 2,3-diethoxy-7-chloropyrido[2,3-fr]pyrazine.46... 

Piperazine Derivatives. Treatment of piperazine-2,5-diones with an excess of triethyloxonium fluoroborate gives 2,5-diethoxy-3,6-dihydropyrazines (390), which can be oxidized to the parent pyrazines (391) by dichloro-cyanobenzoquinone. c/s-Diben lpiperazin ione gives a mixture of cis- and /ra j-dihydropyrazines (390). Pyrolysis of the /ro s-isomer gives 3-benzyl-2,5-diethoxypyrazine (392) in high yield with the elimination of... 

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