2 Mercapto 4 hydroxy-5 cyano

B. 2-Mercapto-4-hydroxy-5-cyanopyrimidine. The aqueous filtrate from which the crude 2-mercapto-4-amino-5-carbethoxy-pyrimidine separated is cooled overnight at 0°, and the cyano-pyrimidine that precipitates is collected on a suction filter. The crude product is recrystallized from about 200 ml. of 10% acetic acid with 1 g. of decolorizing charcoal added. Two additional recrystallizations done similarly give the pure cyanopyrimidine as faintly yellow crystals, m.p. 265-272° (dec.) (Note 3). The yield is 10-18 g. (7-12%). 

Mono- and di-thiocyanato-1,2,4-thiadiazoles, obtained by the stepwise action of cyanogen bromide on barium 3,5-dimercapto-l,2,4-thiadiazole, and on 5-chloro- and 5-hydroxy-3-mercapto-1,2,4-thiadiazole, are somewhat labile. The structures of certain of their transformation products (e.g. mono- and di-sulfides), which may have one of several isomeric forms, are not fully elucidated. The reactivity of their cyano group, resembling that in cyanogen halides, is noteworthy it is easily removed by the action of alkalis, the parent thiol being regenerated.202... 

Treatment of diphenylacetonitrile in toluene with sodium amide and 2-chloro-pyrazine gave 2-(C-cyano-C,C-diphenylmethyl)pyrazine (1021), and 2-vinylpyrazine with phenylacetonitrile and sodium heated at 120-130° for 10 minutes gave 2-(3 -cyano-3 -phenylpropyl)pyrazine (731). 2-Amino-5-bromomethyl-3-cyano-pyrazine with sodium hydride and methyl cyanoacetate in tetrahydrofuran formed the dialkylated product (56) (1031). 2-Amino-3-mercapto-5,6-dimethylpyrazine in methanol with potassium hydroxide and chloroacetonitrile gave 2-amino-3-cyanomethyIthio-5,6-dimethylpyrazine (1229), and 2-carboxypyrazine refluxed with chloroacetonitrile and triethylamine in ethyl acetate for 45 minutes gave the cyanomethyl ester (1317). 2-Hydroxy 5-methyl-3-propylpyrazine with cyanogen halides in aqueous sodium hydroxide-dimethylformamide at 0-5° gave l-cyano-5-methyl-2-oxo-3-propyl-l, 2-dihydropyrazine (1123). 

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). 

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