2-Amino-3-cyano-5-phenylpyrazine

The reductive decyanation of cyanopyrazine using H2 and Pt/C under acidic conditions has been reported <2002TL6747>, that is, 2-amino-3-cyano-5-phenylpyrazine 1-oxide 73 is hydrogenated to 2-amino-5-phenylpyra-zine 74 in 90% yield (Equation 11). The double reduction has also been shown to be realized with sodium dithionite. 

The reactions of various chlorophenylpyrazines with potassium amide in liquid ammonia have been investigated in detail (827). Treatment of 2-chloro-3-phenylpyrazine with potassium amide in liquid ammonia gave only 2-amino-3-phenyl-pyrazine, but 2-chloro-6-phenylpyrazine gave 4(5)-phenylimidazole and 2-cyano-4(5)-phenylimidazole, and 2-chloro-5-phenylpyrazine gave a mixture of 2-amino-5-phenylpyrazine, 4(5)-phenylimidazole, and 2-cyano-4(5)-phenylimidazole. The 2[Pg.125]

Phenylpyrazine 1-oxide, 2,3-diphenylpyrazine 1-oxide and 2,5-diphenylpyrazine 1 -oxide have been deoxygenated in good yield by aqueous chromium(ll) chloride in methanol, acetone, and chloroform at room temperature (761), and deoxygenation of 5-(substituted aminomethyl)-2-amino-3-cyano-6-methylpyrazine 1-oxide by triethyl phosphite in hot dimethylformamide has been described (762). 

Finally, 3-amino-2-cyano-5-phenylpyrazine and ethyl chloroformate gave the N-ethoxy carbonyl derivative 128, which cyclized with loss of ammonia to l-methyl-7-phenylpteridine-2,4-dione in boiling methanolic sodium methoxide (moderate yield).181... 

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