Hydrazides from diazonium salts

The products from the reaction of alkene diazonium salts (266 X = SbCle or BF4) with acyl hydrazides are dependent on the nature of the substituents (R and R ) on the alkene <85CB4026, 89ZN(B)587>. With the 4-methoxystyryl derivative (266 R =OMe, R = 4-MeOQH4) only 1,3,4-oxadiazoles (267) are produced (17-40%), whereas with ketene acetals (266 R = OMe, R = OEt)... 

The use of diazonium salts instead of nitrous acid to convert aromatic hydrazides to azides has received very little study, though it is a potentially applicable method for hydrazides carrying other functional groups which might be attacked by nitrous acid. For example, p-phenyl-enediamine has been obtained in this way from p-aminobenzhydrazide (see p. 353). The cold, aqueous solution of 1 equivalent -of diazonium salt is added to a cold solution of the hydrazide containing excess acid. If precipitation of the azide does not begin at once, the addition of sodium acetate usually initiates it. Under special conditions, the intermediate diazo hydrazides, RCONHNHN =NAr, can be isolated and... 

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