2-Chloro-3-hydrazinopyrazine

Dichloropyrazine 4-oxide (93, R = Cl) gave 2-chloro-6-hydrazinopyrazine 4-oxide (93, R = NHNH2) (H2NNH2.H20, EtOH, 20°C, 24 h 69%).891 Also other examples.78,80,276... 

Chloro-6-hydrazinopyrazine (207) gave 2-(2-benzamidoethylidene)hydrazino-6-chloropyrazine (208) [C1CH=C(NHBz)C02H, Et3N, EtOH, reflux, 11 h ... 

Dichloropyrazine with hydrazine in ethanol gave 2-chloro-3-hydrazino-pyrazine (828, 919) and 2,6-dichloropyrazine with hydrazine hydrate in ethanol gave 2-chloro-6-hydrazinopyrazine (919, 973). 2,3,5-Trichloropyrazine with hydrazine gave 2,5-dichloro-3-hydrazinopyrazine (919). 

Chloro-3-hydrazinopyrazine (217) gave 2-chloro-3-[4-(ethoxycarbonylmethyl)-(thiosemicarbazido)]pyrazine (218) (Et02CCH2NCS, CHC13, reflux, 1 h 63%), which underwent cyclization with loss of HC1 to afford 3-ethoxycar-... 

Chloro-3,6-difluoro-5-hydrazinopyrazine 2-Chloro-3,6-difluoro-5-methoxypyrazine 2-Chloro-3,6-diisobutyl-5-methoxypyrazine 2-Chloro-3,6-diisobutylpyrazine 2-Chloro-3,6-diisobutylpyrazine 1, 4-dioxide... 

Tetrafluoropyrazine has been converted to 2,3,5-trifluoro-6-hydrazinopyrazine and thence to 2-chloro- and 2-bromo-3,5,6-trifluoropyTazine by reaction with ferric chloride in concentrated hydrochloric acid and cupric bromide in aqueous... 

When 2-amino-5-chloro-3-methoxycarbonylpyrazine was refluxed with aniline and concentrated hydrochloric acid in acetone for 16 hours, the anil, 5-anilino-2-isopropylideneamino-3-methoxycarbonylpyrazine (22) was formed (432, 778, 780), and 2-amino-5-chloro-3-methoxycarbonyl-6-(l -methylhydrazino)pyrazine with benzaldehyde in ethanol gave 2-amino-6-(2 -benzylidene-r-methylhydrazino)-5-chloro-3-methylcarbonylpyrazine (23) (809). A series of hydrazones has been prepared by refluxing equimolar quantities of 2-hydrazinopyrazine and carbonyl compounds in the presence of catalytic quantities of p-toluenesulfonic acid in benzene (1195). Other preparations of similar hydrazones have been described (1196). 

Although 2,6-diamino-3-chloro-5-methoxycarbonylpyrazine was sufficiently reactive to condense with many guanidines, some aliphatic amines, and hydrazine, it failed to condense with weak nitrogen bases such as 2-hydrazinopyrazine. Owing to interest in analogues of the effective potassium-sparing diuretic 2,6-diamino-3-chloro-5-guanidinocarbonylpyrazine, effort has been directed to the preparation of active esters (1331). 

Benzyl D-ribofuranosylthioformimidates (711) reacted with 3-chloro-2-hydrazinopyrazine to form the 8-benzylthio-l,2,4-triazolo[4,3-n]pyrazin-... 

Benzyl D-ribofuranosylthioformimidates (711) reacted with 3-chloro-2-hydrazinopyrazine to form the 8-benzylthio-l,2,4-triazolo[4,3-a]pyrazin-3-yl C-nucleosides 712 as a result of nucleophilic displacement of the chloro group by the benzyl mercaptan produced from the initial cyclocondensation step. Compounds 713 were transformed to the formycin and formycin analogs 714 and 716 (79JOC1028 84JMC924) (Scheme 183). Compound 714 inhibited growth of L1210 tumor cells in culture, has weak antiviral activity, and acted as a coronory vasodilator (84JMC924). 

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