5.6- Dimethyl-2,3-pyrazinedicarboxylic

Dimethyl 3,6-dimethyl-2,5-pyrazinedicarboxylate Dimethyl 5.6-dimethyl-2,3-pyrazinedicarboxylate Dimethyl 5,6-dioxo-l,4,5,6-tetrahydro-2,3-pyrazinedicarboxylate... 

Since 1,4-dihydropyrazine itself is unknown, various substitutions of the ring system are required to produce stable isolable molecules. Carbonyl-stabilized 1,4-dihydropyrazines are synthesized by self-condensation of 3-chloromethyl-5,6-dihydro-l,5,5-trimethyl-2(l//)-pyrazinone <1998J(P1)289>. Another carbonyl-stabilized example is provided by WA -BOC-protected 1,4-dihydropyrazine 102, which can undergo Michael addition with nucleophiles such as 1,2,4-triazole, 3-formylindole, 4-bromothiophenol, benzylamine, or sodium methoxide to yield tetrahydropyrazines 103 (Scheme 26) <2004T8489>. Treatment of the di- and tetrahydropyrazines with trifluoroacetic acid leads to cleavage of BOC groups and/or elimination of the nucleophile to both afford dimethyl 2,5-pyrazinedicarboxylate 104. 

Ethyl 2-acetyl-2-aminoacetate hydrochloride (231) gave diethyl 3,6-dimethyl-2,5-pyrazinedicarboxylate (232) (Et3N, EtOH, air, 20°C, 6 h 90%).39... 

Methyl 2-hydroxyimino-3-oxobutyrate (242) gave dimethyl 3,6-dimethyl-2, 5-pyrazinedicarboxylate (243) (TiCl3, H20—MeOH, AcONa, pH 7, A, 20°C, 3 h then air [ until white 30%).300... 

The sole example of this transformation involved treatment of 3,4-diphenyl-1,2,5-selenadiazole (78) with dimethyl acetylenedicarboxylate in benzene at 150°C (sealed) for 20 h to afford dimethyl 5,6-diphenyl-2,3-pyrazinedicarboxylate (79) in 16% yield.1084... 

Dimethyl 2,3-pyrazinedicarboxylate gave l-ethyl-2,3-dimethoxycarbonylpyrazinium tetrafluoroborate (347) (Et3OBF4, C1CH2CH2C1, reflux, 2 h 80%) 415 methyl 2-pyrazinecarboxylate gave 3-methoxycarhonyl-l -methylpyrazininm iodide (348)... 

Dimethylamino-7V-hydroxy-2-pyrazinecarboxamide 6-Dimethylamino-7V-hydroxy-2-pyrazinecarboxamidine 2-Dimethylamino-5-iodopyrazine 2-Dimethylamino-6-iodopyrazine 2-Dimethylamino-5-iodopyrazine 4-oxide 2-Dimethylamino-3-isobutylpyrazine 2-Dimethylamino-6-isobutylpyrazine 2-Dimethylamino-5-methoxy-3,6-dimethylpyrazine 2-Dimethylaminomethyl-3,6-bismethylthiopyrazine 2-Dimethylamino-6-methyl-5-phenylpyrazine 4-oxide 2-Dimethylamino-3-methylpyrazine 2-Dimethylamino-6-methylpyrazine 2-Dimethylamino-3-methylpyrazine 4-oxide Dimethyl 5-amino-6-oxo-1,6-dihydro-2,3-pyrazinedicarboxylate 2-Dimethylamino-5-phenylpyrazine 2-(3-Dimethylaminopropyl)-6-methylpyrazine... 

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