Preparation of substituted hydrazines from hydrazones or azines

Hydrazones and azines can be reduced to A,iV -disubstituted hydrazines either catalytically or by metal hydride complexes.27d Sodium amalgam has also been applied successfully in a few cases to reduction of the C=N double bond of hydrazones.37,38 In general, hydrazones and azines of ketones are reduced more easily than their aldehyde analogs. 

Zymalkowski, Katalytische Hydrierung im organisch-chemischen Laboratorium, F. Enke-Verlag, Stuttgart, 1965, p. 203. 

Alteration of nitrogen groups in carbon-nitrogen compounds 

Sodium tetrahydridoborate has proved particularly valuable for reduction of 2,2-bis-(2-chloroethyl)hydrazones of aliphatic ketones 48 

A solution of sodium tetrahydridoborate (0.5 mole per mole of hydrazone) in a few ml of water and a little alcohol is dropped rapidly, with stirring, into a solution of a hydrazone (5 g) in ethanol (50 g) cooled to —15°. Stirring is continued at —15° to —10° for a further 2 h, then methanolic hydrochloric acid is added until the mixture is acidic. The solution is filtered from sodium chloride and evaporated, and the hydrochloride obtained is recrystallized from ethanol. Yields amount to 75-95 %. 

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