2.3- Dichloro-5.6-diphenylpyrazine

Diphenylpyrazine 1,4-dioxide (46) gave a separable mixture of 2,3-dichloro-5,6-diphenylpyrazine (47) and (unexpectedly) 2-chloro-5,6-diphenylpyrazine... 

Methyl 6-amino-5-cyano-3-methyl-2-pyrazinecarboxylate 1-oxide Methyl 3-amino-5-cyclohexyl-2-pyrazinecarboxylate Methyl 3-amino-6-cyclohexyl-2-pyrazinecarboxylate Methyl 3-amino-6-cyclopropyl-2-pyrazinecarboxylate Methyl 3-amino-5,6-dichloro-2-pyrazinecarboxylate Methyl 3-amino-5-dimethylamino-6-methyl-2-pyrazinecarboxylate Methyl 3-amino-5-dimethylamino-6-phenyl-2-pyrazinecarboxylate Methyl 3-amino-5-dimethylamino-2-pyrazinecarboxylate Methyl 3-amino-5,6-dimethyl-2-pyrazinecarboxylate 2-Methylamino-3,5-diphenylpyrazine 2-Methylamino-3,6-diphenylpyrazine... 

Chloro-2,S-dimethylpyrazine was not isolated from the reaction of DL-alanine anhydride with a mixture of phosphoryl chloride and phosphorus pentachloride, but the reaction gives a poor yield of (48, X = Q) and a small quantity of (48, X = OH). Gallagher et al. (282) found that DL-phenylglycine with phosphoryl chloride gave 2,5-dichloro-3,6-diphenylpyrazine and 3-hydroxy-2,5-diphenyl-pyrazine (presumably formed by loss of the elements of hydrogen chloride from an intermediate 2-chloro-5-hydroxy-3,6-diphenyldihydropyrazine) and Dunn et al. (95) from DL-leucine anhydride and phosphoryl chloride prepared flavacol, 3-hydroxy-2,5-diisobutylpyrazine, and a mature of chloropyrazines, whereas Ohta (101) used phosphoryl chloride and phosphorus pentachloride and obtained flavacol and a little 2[Pg.26]

Whereas 2-hydroxy-3-nitro-5,6-diphenylpyrazine with phosphoryl chloride at reflux has been shown to give a mixture of 2-chloro-3-hydroxy- and 2,3-dichloro-... 

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-... 

Refluxing phosphoms tribromide converted 2-bromo-3-hydroxy-5,6-diphenyl-pyrazine and 2-bromo-5-hydroxy-3,6-diphenylpyrazine to the dibromopyrazines 2,3-dichloro-5,6-dimethylpyrazine and 2,5-dichloro-3-phenylpyrazine to the dibromopyrazines (817) 5-chloro-2,3-diphenylpyrazine (and its 6-ethyl derivative) to 5-bromo-2,3-diphenylpyrazine (and its 6-ethyl derivative) (866) and 2-hydroxy-... 

Bromo-3-hydroxy-5,6-dimethylpyrazine and 2-bromo-5-hydroxy-3,6-diphenyl-pyrazine with phosphoryl chloride afforded 2,3-dichloro-5,6-dimethylpyrazine and 2,5-dichloro-3,6-diphenylpyrazine, respectively (817) and the bromo substituent in 2-amino-3-bromo-5,6-dimethylpyrazine and its p-aminobenzenesulfonyl derivative have been replaced by chlorine on treatment with aqueous hydrochloric acid in ethanol (812). 

Dichloro-3,6dipropyl(or 3,6-diisopropyl or 3,6diisobutyl)pyrazine heated with hexamethylphosphoramide at 200° for 2-3 hours gave 81% 2-chloro-5-dimethylamino-3,6-dipropyl(or 3,6diisopropyl or 3,6-diisobutyl)pyrazine (937), but 2,6-dichloro-3,5diphenylpyrazine heated with hexamethylphosphoramide at 200° for 3 hours gave 64% 2,6-bisdimethylamino-3,5-diphenylpyrazine (937). 

Methoxypyrazines (31) have been prepared by diazomethane methylation of 2-hydroxy-3-isobutylpyrazine (60, 311, 367), 2-hydroxy-3-isopropylpyrazine (59, 367), 2-hydroxy-3-propyl(ethyl or hexyl)pyrazine (367), 3-hydroxy-2-isobutyl-5(and 6)methylpyrazine and 2-hydroxy-3-isobutyl-5,6-dimethylpyrazine (368), 2,3-dihydroxypyrazine (832), 2-hydroxy-5-methoxy- and 2,5-dihydroxy-3,6-diphenyl-pyrazine (832), 2-hydroxy-6-methoxy(and benzyloxy)pyrazine (832), 2,6-dihydroxy-3,5-diphenylpyrazine (873), 2,3,5-trifluoro-6-hydroxypyrazine (851), 2-chloro-6-hydroxy-3,5-diphenylpyrazine (873), 2-chloro-6-hydroxy-5-methyl-3-phenylpyrazine (873), 2-chloro-6-hydroxy-3-methyl-5-phenylpyrazine (873), 5,6-dichloro-1 -cyclohexyl-34iydroxy-2-oxo-l, 2-dihydropyrazine (853), 2-chloro-5-hydroxy-3-methoxy-6-methoxycarbonylpyrazine (881), 2-(4 -amino-3, 5 -dibromo-phenylsulfonamido)-3Tiydroxy-6-methoxypyrazine (881), 2-amino-3-hydroxy-... 

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