Tetrazolium betaines

Formazans are stable in alkaline solution. Alkaline hydrolysis of functionalities on formazans such as nitriles, esters, and amides leads to the acids (Section 7.3.1.1). The case of 3-nitroformazans (198) is unique. Reaction with hydroxide ion gives 3-hydroxy formazan (199) which can be readily oxidized to the tetrazolium betaine. In the presence of hydrosulfide, a reduction of the nitro group takes place giving 3-aminoformazan (200) with traces of the 3-mercaptoformazan (201), which by contrast is the main product when ammonium polysulfide is used (Scheme 30).45,346... 

The prepn of a variety of 3,5-diatyl-l-(5 -tetrazolyl)(lH) tetrazolium betaines by introducing electronegative substituents in the benzene residue of l-fS -tecrazolyl) -phenyltetrazene, together with the use of substituted benzaldehydes is reported (Ref 3) Refs 1) J.P. Horwitz V.A. Grakauskas, JOrgChem 19, 194-201 (1954) CA 49, 3173 (1955) 2) Ibid, JACS 77, 6711 (1955) CA... 

Diphenyl-TetrazoJyl-Oxide ( ) [C-Oxy-diphenyl-tetrazolium-betain, Diphenylcarbodia-zone or 2,3-Diphenyl-5-oxytetrazolium hydroxide (Ger)]... 

A soln. of 2 moles p-ethoxybenzenediazonium chloride prepared from p-phe-netidine and Na-nitrite in aq. HGl added at 0-3° during 3-5 min. to a soln. of bis (phenylsulfonyl) methane in aq. 5%-NaOH of pH 11-12, and stirred 24hrs. at room temp. 5-hydroxy-l,3-di-(p-ethoxyphenyl)tetrazolium betaine. Y 61%. 

The chemistry of tetrazolium thiolates and other mesoionic tetra-zoliums has been extensively reviewed.297,298 Tho ugh there are no reports of the chemical reduction of thiolates to formazan-like structures, the polarographic reduction of the complex betaines (146) to formazans has been reported.655... 

Disubstituted tetrazolium salts (78) can be deprotonated with tri-ethylamine (70TL3453). Fragmentation of the resulting betaines gives car-bodiimides, and, since the tetrazolium salts can be prepared with a variety of substituents R , this provides a method for the generation of unsym-metrical carbodiimides with unusual substituents (e.g., R = vinyl or diethylamino). 

Formazans 110 have been oxidized in aqueous alkaline solution with K2Mn04 or K3Fe(CN)5 to the tetrazolium tetrazolate betaines 111 (73KGS1570 74KGS268) [Eq.(27)]. 

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