Pyrazines reactions

A variation on the usual synthesis of pyrazines, reaction of 1,2-diones with diamines, was the use of the diazabutadiene 81 in place of the dione <06JOC5897>. In another paper, the same diaza compound 81 reacted with sarcosine methyl ester, in a complex set of reactions, to produce quite good yields of 5-oxy-pyrazine-2-carboxamides 82. The A-methyl was lost and direct aromatisation occurred, presumably, due to cleavage oftheN-N bond <06SL2403>. 

Pyrimido[5,4-c]-l,2,5-oxadiazinones (417) are suitable starting materials to construct annulated pyrazines. Reaction with carbanions derived from CH-acidic compounds, activated by two different electron-withdrawing functions, proceed in a regioselective manner by initial attack at the N—O bond. Triethyl phosphonoacetate, /f-ketophosphonates, nitro ketones, nitro esters, sulfonylacetates, and JV-acetoacetylglycine have been applied to form 6,7-disubstituted lumazines (418) (Equation (18)) <91H(32)79>. 

In the pyrazine series, the Mannich reaction was applied first to 2,5-dimethyl-pyrazine by Linder and Spoerri (715). Of the amines tried, positive reactions were obtained only with dime thy lamine, piperidine, and morpholine, and it was found that one, or more usually two, of the hydrogen atoms of each of the methyl groups could be substituted. Thus 2,5-dimethylpyrazine, dimethylamine hydrochloride, and formalin in refluxing isopentyl alcohol gave 2,5-bis[bis(dimethylaminomethyl)-methyl]pyrazine and 2,5-bis(j3-dimethylaminoethyl)pyrazine. Reaction of 2-methyl-pyrazine with formalin and diethylamine hydrochloride gave 2- 3-diethylamino-ethylpyrazine (716) similarly dimethylamine hydrochloride gave 2-dimethyl-aminoethylpyrazine (17) and some 2-[bis(dimethylaminomethyl)]methylpyrazine (18) (657). 

The Diazines Pyridazine, Pyrimidine, and Pyrazine Reactions and Synthesis... 

The Diazines Pyridazine, Pyrimidine, and Pyrazine Reactions and Synthesis 259 Stannanes can be prepared via nucleophilic displacements at low temperature." ... 

Imidazo[4,5-fe]pyrazine, 2-methyl-synthesis, 5, 645 lmidazo[l,2-a]pyrazines reactions, 5, 624 synthesis, 5, 642-643 Imidazo[ 1,5-a]pyrazines chlorination, 5, 625 reactions, 5, 625-626 synthesis, 5, 644-645 Imidazo[4,5-fc]pyrazines reactivity, 5, 626-627 synthesis, 5, 645-646... 

The diazines pyridazine, pyrimidine, and pyrazine reactions and synthesis... 

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