Cleavage hydrazo compounds

Hydrazo compounds were hydrogenolyzed to primary amines by catalytic hydrogenation over palladium [740]. Since hydrazo compounds are intermediates in the reductive cleavage of azo compounds to amines it is very likely that all the reducing agents converting azo compounds to amines cleave also the hydrazo compounds (p. 96). 

Oxidative cleavage of amines 9-39 Reduction of amides 9-47 Reduction of nitro compounds 9-50 Reduction of nitroso compounds or hydroxylamincs 9-51 Reduction of oximes 9-52 Reduction of azides 9-53 Reduction of isocyanates, isothiocyanates, or N-nitroso compounds 9-55 Reduction of amine oxides 9-59 Reduction of azo, azoxy, or hydrazo compounds... 

Elimination of HI, which in the presence of an excess of IN3 can form hydrazoic acid, followed by its addition to the vinyl azides can give an intermediate triazide 75. The same compound could arise directly by substitution of one iodine atom by an azido group. The intermediate 75 has been considered to undergo a transannular reaction with homolytic cleavage of the weak C—I bond to form the radical 76, which loses a nitrogen atom to a radical 77. Combination of the two radicals leads to the 2-tetrazene 74 (equation 77). 

It will be seen that the cleavage of the hypothetical hydrazo derivatives to the hypothetical imino compounds obviates the necessity of assuming direct oxidation by phenylhydrazine. Fieser and Fieser inquire why osazone formation ceases with the introduction of two phenylhydrazine residues, and seek to explain this fact by the postulation of chelate tautomeric ring structures XLIII or to the existence of a resonance... 

---