By Hydrolysis of Other Substituted Pyrazines

Alkaline hydrolysis of 2,5-dicyano-3,6-diphenylpyrazine gave 2-carboxy-5-hydroxy-3,6-diphenylpyrazine, and analogous reactions were observed with the 

Irradiation of pyrazine derivatives with an a-carbonyl substituent under an atmosphere of nitrogen has given hydroxypyrazines. Thus 2,5-dimethoxycarbonyl- 

6- dimethylpyrazine in diethyl ether irradiated with an USHIO UM425 450-W high-pressure mercury lamp for 6 hours resulted in a 23-54% yield of 2-hydroxy-5-methoxycarbonyl-3,6-dimethylpyrazine and 1,4-dihydropyrazines. 2,5-Diacetyl- 

6- dimethylpyrazine similarly treated gave 2-acetyl-5-hydroxy-3,6-dimethyl-pyrazine, and other hydroxypyrazines were prepared likewise (1064). 

Hydrolysis of 2-hydroxy-3-nitro-5,6-diphenylpyrazine (11) in aqueous sulfuric acid or aqueous hydrochloric acid-acetic acid afforded 2,3-dihydroxy-5,6-diphenyl-pyrazine (817, 1065), and similar results were obtained with dry hydrogen chloride in glacial acetic acid (841). 

---