Preparation of Hydrazino-and Hydrazonoquinoxalines

The major preparative routes to hydrazinoquinoxalines, by primary synthesis (Chapter 1) and by hydrazinolysis of halogenoquinoxalines (Sections 3.2.1 and 3.4.1) have been covered already minor routes by hydrazinolysis of alkoxy-, alkylthio-, alkylsulhnyl-, or alkylsulfonylquinoxalines do not appear to have been used recently. 

However, at least two other minor routes have been used. Thus reduction of 2-hydroxyaminoquinoxaline (209) gave A, A -di(quinoxalin-2-yl)hydrazine (210) (CoCl2 -6H20, THF, reflux, 1 h % LiAlHa, THF, 20°C, 10 min 62%) and reduction of 2,2 -azoquinoxaline (211) gave the same product (210) (NiCl2 -6H20, MeOH, NaBH4 slowly, 20°C, 30 min 76% 1,2,3,4-tetrahydronaphthalene, reflux. 

Nearly all (extranuclear) hydrazonoquinoxalines are made by treatment of quinoxaline aldehydes, ketones, or their acetals with hydrazine or substituted hydrazine, but a few are produced by diazo coupling. These reactions are illustrated by the following examples. 

2-Quinoxalinecarbaldehyde (212) gave 2-p-bromophenylhydrazonomethylqui-noxaline (213, R = C6H4Br-p) (p-BrCeH4NHNH2, MeOH, 20°C, 1 h  

3-Quinoxalinedicarbaldehyde gave 2,3-bis(phenylhydrazonomethyl)quinoxa-line (214) (PhNHNH2, EtOH, reflux, 30 min -90%).  

2-Quinoxalinecarbaldehyde 4-oxide (215) gave 2-(tosylhydrazonomethyl) quinoxaline 4-oxide (215) (TsHNNH2, MeOH, reflux, 30 min 95%).149 

3-[a-(m-Fluorophenylhydrazono)-a-formylmethyl]-l-methyl-2(l/7)-quinoxalinone (216, X = 0) gave 3-[2-(benzoylhydrazono)-l-(m-fluorophenylhydrazo-no)ethyl] -1 -methyl-2( 177)-quinoxalinone (216, X = NNHBz) (BzHNNH2, EtOH, reflux, 15 min 73%).612 

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