Arylhydrazines, from diazonium salts

The reduction of diazonium salts by sodium sulfite forms monosub-stituted arylhydrazines. An improved procedure for the synthesis of phenylhydrazine in 84% yield is typical. Arylhydrazine salts substituted in the nucleus with halo," ether, carboxyl, or nitro groups have been prepared. The free bases are liberated from the salts by the action of aqueous sodium hydroxide or sodium acetate. 

A high-yield conversion of arenediazonium fluoroborates into the corresponding arylhydrazines occurs in methylene chloride, using benzeneselenol, PhSeH, while the reaction of diazonium salts with Janovsky cr-complexes (180) formed from m-dinitrobenzene and MeCOCH gives (181) and (182) by displacement of the nitro-group with the diazonium residue (Scheme 28). 

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