Pyrazine 2.3- dicyano-5,6-diphenyl

The self-condensation of the bisulfite addition compound of an a-oximinoketone followed by reaction with potassium cyanide and hydrochloric acid yields 3,6-dicyano-2,5-dialkylpyrazines or, in the case of oximinoacetophenone, a mixture of 3-cyano-2,5-diphenyl-pyrazine and 3,6-dicyano-2,5-diphenylpyrazines.227... 

Some chlorinations have been reported with thionyl chloride. 23-Dicyano-5,6-dihydroxypyrazine refluxed with thionyl chloride in pyridine was reported to give 23-dichloro-5,6-dicyanopyrazine (862) and 2-hydroxy-3-nitro-5,6-diphenyl-pyrazine with thionyl chloride gave 2-chloro-3-hydroxy-5,6-diphenylpyrazine (817, 841) but with thionyl chloride and pyridine it gave the betaine of 2-hydroxy-5,6-diphenyl-3-pyridiniopyrazine chloride (5) (863), which was hydrolyzed in acid to 2,3-dihydroxy-5,6-diphenylpyrazine (863). No product could be isolated from 2-methylpyrazine when refluxed with thionyl chloride (864). 1,4-Dimethylpiperazine-... 

The following nitriles have been used to prepare carboxypyrazines 2-cyano-3-phenyl [NaOH/ethylene glycol/reflux (1274) or heated with H2S04/NaN02 (1024)] 3-cyano-2,5-dimethyl (NaOH/EtOH/reflux) (1015) 3-cyano-2,5-diphenyl (NaOH) (286) 2,3-dicyano [NaOH/EtOH (354) aq. KOH/EtOH (353) NajOj (357)] 2,6-dicyano (5% NaOH/10072h)(865) 23-dicyano-5,6-dimethyl(Na202) (357) 2-cyano-6-ethylthio(propylthio or phenylthio) (NaOH/EtOH/reflux) (992) 2hydrochloric acid to 2-(3 -carboxy-3 -phenylpropyl)pyrazine (731). 

When heated with aqueous potassium hydroxide, 2,5-dicyano-3,6-dimethyl(and diphenyOpyrazine gave 2-carboxy-5-hydroxy-3,6-dimethyl(and diphenyl)pyrazine (286-288) and the diethyl analogue was prepared similarly (287). 2-ChIoro-6-cyanopyrazine refluxed with three equivalents of sodium methoxide for 2 hours gave 2-carboxy-6-methoxypyrazine, also obtained from 2-chloro-6-cyanopyrazine with one equivalent of sodium methoxide through 2-(C-imino-C-methoxymethyl)-6-methoxypyrazine (2), which, refluxed with 15% sodium hydroxide, gave 2-carboxy-6-methoxypyrazine (986). 

Dicyanopyrazine with sodium methoxide in methanol with ammonia at reflux gave 5,7-diimino-6//-pyrrolo[3,4-i)]pyrazine (65) (1442) and 2,3-dicyano-5,6-dimethyl(and 5,6-diphenyl)pyrazine with hydrazine by the procedure of Patel and Castle (1339) gave 2,3-dimethyl(and 2,3-diphenyl)-5,8-diaminopyrazino[2,3-rfJ-pyridazine(s) (66) (1435). Fusion of 2-chloro-3-cyano-5,6-diphenylpyrazine with urea and thiourea was reported to give 4-amino-2-hydroxy(and mercapto)-6,7-diphenylpteridine (848). 

Heating of l,4-dicyano-2,3-dinitroso-2,3-diphenylpiperazine ( ) (1572, cf. 1573) in mesitylene is claimed to give l,4-dicyano-2,3-diphenyl-1,4,5,6-tetrahydro-pyrazine (1572), and l-carbamoyl-3-hydroxy-2,3-diphenylpiperazine ( )(1572, cf. 1573) with methyl iodide and potassium carbonate in methanol is claimed to give 4-carbamoyl-l,l-dimethyl-2,3-diphenyl-l,4,5,6-tetrahydropyrazinium iodide (1572). 2-Diethylamino-l,4-dimethylpiperazine on thermal treatment gives 1,4-dimethyl-l,2,3,4-tetrahydropyrazine, which was methoxycarbonylated to 5-methoxycarbonyl-1,4-dimethyl-l, 2,3,4-tetrahydropyrazine (1593). 

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