From hydrazo compound

Kenner and Knight point out that hydrazones are formed from free hydrazine bases, whereas hydrazine salts, such as phenylhydrazine acetate, yield osazones. It is emphasized that salt formation greatly favors such reactions as the production of amines from hydrazo compounds, a reaction which is represented as follows. The cation therefore... 

Azo compounds Hydrogen abstraction Oxo compounds from alcohols Azo from hydrazo compounds... 

Similar experiments on the analysis of the products from the three isomeric hy-drazonaphthalenes30 and substituted hydrazobenzenes31 confirm the intramolecu-larity of the reaction. In addition, products resulting from attack on the solvent of fragments from a hydrazo-compound during rearrangement have never been detected30. 

Isocyanates and isothiocyanates are reduced to methylamines on treatment with LiAlH4. Lithium aluminium hydride does not usually reduce azo compounds (indeed these are the products from LiAlH4 reduction of nitro compounds, 19-59), but these can be reduced to hydrazo compounds by catalytic hydrogenation or with... 

Hydrogenation of nitro groups may be stopped at the hydrazo stage with a proper catalyst and inhibitors. As shown in Fig. 2.31, the hydrazo compounds result from condensation of the nitroso and hydroxylamine and can be maximized or minimized (see the later discussion of nitroso group hydrogenation) depending on conditions. For example 2,2 -dichlorohydra-zobenzene can be prepared in 90% yield (Fig. 2.35).280... 

Unless a 2% excess of N-bromosuccinimide is used, the azo compound is contaminated by an impurity, possibly the original hydrazo compound, which separates along with the desired product in the form of long, easily distinguished needles. The two substances cannot be separated by crystallization from ligroin. 

With concentrated mineral acids azobenzene gives red salts, as may be shown by pouring hydrochloric acid on it. Addition of hydrogen leads to the re-formation of the hydrazo-compound. Oxygen is added on and the azoxy-compound formed by the action of hydrogen peroxide or nitric acid. The synthesis of asymmetrical aromatic azo-compounds from nitroso-compounds and primary amines was discussed above. 

The reduction of azo compounds to hydrazo compounds is also achieved by means of aryltellurols or sodium hydrogen telluride. The last reagent (generated from NaBH4 and... 

Reduction of azobenzenes in an aprotic solvent generates nucleophilic nitrogen species, which can react with an added alkyl halide. In this way, cyclic hydrazo compounds can be generated from a,o>-dibromoalkanes [t07]. 

Pyridine reacts with sodium hydrazide in the presence of hydrazine to yield 2-hydrazinopyridine in the absence of free hydrazine a hydrazo compound is formed (Scheme 88) (64AG(E)342). A difference between hydrazination and amination is the formation of 1,4-adducts which cannot be rearomatized even on heating. This is reflected in the behaviour of quinoline, which gives only a 0.5% yield of a -hydrazino product, whereas 4-methylquino-line is hydrazinated in 76% yield (64AG(E)342). Acridine behaves differently with sodium hydrazide/hydrazine, 9,10-dihydroacridine is formed almost quantitatively, but reaction in the absence of hydrazine yields 9-aminoacridine (65%). An even higher yield of 9-amino-acridine is obtained when sodium Af.AC-dimethylhydrazide is used (Scheme 89). Good evidence for intermediacy of (151) comes from the isolation of (152) on hydrolysis of (151). 

The formation of hydrazoic acid and its derivatives together with ammonia from diazo compounds under the influence of hydrazine or its derivatives was explained by Thiele [68]. At an intermediate stage a diazohydrazine, e.g. C6H5N2NHNH2, is formed which then undergoes decomposition according to two parallel reactions ... 

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