4,5-Dimethyl-2,3-pyrazinedicarboxylic acid

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. 

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