Benzenediazonium chloride formazans

Acyclic sugar hydrazones react with benzenediazonium chloride to give red formazans. When oxidized with N-bromosuccinimide (or, after acetylation, with lead tetraacetate), these yield tetrazolium salts. 

The reaction of phenylhydrazine with oxysucrose was found to be similar to that described for oxidized monosaccharide derivatives above, as only two molecules of the base reacted with the four potential aldehyde groups the product was assigned structure (89). Mester found that this derivative forms an amorphous bis(diphenylformazan) with benzenediazonium chloride, and so he assigned structure (90) to it. Acetylation of the formazan gave an amorphous product, identical with the formazan prepared from... 

Occasionally it is unnecessary to isolate the hydrazone since this is itself accessible by a coupling reaction. Numerous formazans can be obtained by treating compounds containing active methylene groups directly with 2 molar proportions of a diazonium salt. For example, pyruvic acid is converted into 3-oxalo-l,5-diphenylformazan (fi4formazylglyoxalic acid ) in 94% yield by benzenediazonium chloride in potassium hydroxide solution.351 Acyl groups (CH3CO or COOH) are often eliminated in such reactions 343,344,352 thus acetoacetic ester yields ethyl l,5-diphenylformazan-3-carboxylate almost... 

Benzylidenehydrazinophthalazine (132) with benzenediazonium chloride gave l,3-diphenyl-5-(phthalazin-l-yl)formazan (133) (reactants, Me2NCHO, 6M HCl, <0°C 2M NaOH dropwise, 2 h 85% analogs likewise). = ... 

N=N— 1 azobenzene, methyl orange, benzocinnoline, formazane —N N j benzenediazonium chloride, diazotised sulfanilic acid... 

Further evidence for an acyclic structure for glucosazone is provided by the formation of a formazan after treatment with benzenediazonium chloride 238). The osazone may have a six-membered chelate ring formed by hydrogen bonding of the two hydrazine radicals. (See under Hy-drazones.)... 

---