5-Methoxycarbonyl-2,3-diphenylpyrazine

Many derivatives of carboxy chloropyrazines have been prepared by the action of phosphoryl chloride on the corresponding hydroxypyrazine. In this way were prepared 2-chloro-3-methoxycarbonylpyrazine (371, 423, 836), 2-chloro-3-methoxycarbonyl-5,6-diphenylpyrazine (but the corresponding hydroxy compound did not react with phosphorus tribromide) (837), and 3-chloro-2-methoxycarbonyl-... 

Hydrolysis of 2,6-diacetoxy-3,5-diphenylpyrazine (9) (from 2-hydroxy-3,5-diphenylpyrazine 1 -oxide by refluxing with acetic acid-acetic anhydride) with potassium hydrogen carbonate in methanol gave 2,6-dihydroxy-3,5-diphenylpyrazine (873), and 2-acetoxy-6-methoxycarbonylpyrazine (from 3-methoxycarbonyl-pyrazine 1-oxide with acetic anhydride) with methanolic hydrogen chloride gave 2-hydroxy-6 -methoxycarbonylpyrazine (838). 

Chloro-3-methoxycarbonyl-5,6-diphenylpyrazine refluxed with sodium methoxide gave 2-carboxy-3-methoxy-5,6-diphenylpyrazine (371) and the attempted Schmidt reaction of 2,5-dimethoxycarbonylpyrazine, in concentrated sulfuric acid with trichloroacetic acid at 60° with subsequent addition of sodium azide, gave 2,5-dicarboxypyrazine (1176). 2-Methoxy-3-methoxycarbonyl-5,6-diphenylpyrazine, when refluxed with cuprous chloride in dry dimethylformamide, gave 2-carboxy-3-methoxy-5,6-diphenylpyrazine (10%) 2-hydroxy-3-methoxycarbonyl-5,6-diphenyl-pyrazine similarly treated gave 5-hydroxy-2,3-diphenylpyrazine (30%) (837). 

A more aromatic type of lactam, 3-methoxycarbonyl-l-methyl-5,6-diphenylpyrazin-2-one (53), when fused with guanidine carbonate, gave an excellent yield of 2-imino-8-methyl-6,7-diphenylpteridin-4-one (see 10).36... 

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