1.3- Diphenyl-5- formazan

With the synthesis of the benzylidene hydrazones of selenazoles, it was possible to prepare formazans containing a selenazole ring. Of the compounds already described (Section I,C,1), 2-benzylidene-hydrazino-4,5-diphenyl- and 2-benzylidenehydrazino-4-methyl-5-carb-ethoxy-selenazole were used to couple with diazonium salts in order... 

Formazan, l-(2-hydroxophenyl)-3,5-diphenyl-copper(II) complexes dyes, 6, 81... 

Absorption spectra of formazans have been studied in detail. Almost all formazans exhibit UV/visible spectra between 300 and 600 nm.1,2,12,13,40,62,325 326 The absorption maxima are very sensitive to substituent effects. For example, the 1,5-diphenyl formazan 185 when X is hydrogen, methyl, phenyl, cyano, and mercapto shows a band at 420, 410, 470, 504, and 590nm in ethanol, respectively. The 3-chloro derivative 186 when X is hydrogen, iodine, bromine, chlorine, and fluorine has a band at 433,433,430,421, and 417 nm, respectively. Table 13 shows the influence of substituents on the absorption maxima in the trisubstituted formazans 3. Table 14 shows the influence of substituents on the absorption maxima of... 

In the presence of the C-20-ketogroup at the side chain, tetrazolium salts are reduced to the corresponding strongly colored formazans. Mader and Buck were the first to apply tri-phenyl tetrazolium chloride to assay pharmaceutical steroids [83], but it was later found that air affects the procedure leading to poor reproducibility [84,85]. More stable reagents such as 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium bromide [86] and 2,5-diphenyl-3-(p-strylphenyl)tetrazolium chloride [87] were employed successfully. Good results were also obtained with blue tetrazolium, or 3,3 -(3,3 -dimethoxy-4,4 -biphenylene) bis 2,5-diphenyl-... 

ArN-NCRNNHAr by M. Ragno S. Bruno who prepd various nitro derivs [Gazz Chimltal 76, 485—99(1946) and CA 41, 6542(1947)]. For instance, the compd PhN=NC(CN)= NNHPh may be called N,N -Diphenyl-C-cyano formazan or N, N7-Di phenyl-formazylcyanide. Some of the formazan or formazyl derivs give expl salts while others form tetrazoles or other ring compds Note C Metby I formazan is called Acetazidin or Azidin in Beil 2, 4, but the name azidin has been suggested for the radical NgC(—)=NH, which is entirely different... 

Copper and nickel complexes of the tridentate l-(2-carboxyphenyl)-3,5-diphenyl- (169 X = C02 R = R = Ph) and 1-(2-hydroxyphenyl)-3,5-diphenyl-(169 X = 0 R = R = Ph) formazans were prepared118 by the interaction of the formazan and the appropriate metal acetate in alcohol and were assigned the three-coordinate structures (170 X = O, C02 R = R = Ph M = Ni, Cu) since the diamagnetic nickel complexes were found to be unimolecular in benzene solution. Treatment of the nickel complex (170 X = O, R = R = Ph M = Ni) with pyridine gave a violet crystalline adduct which was assigned the four-coordinate structure (171 X = O R = R = Ph M = Ni). A product similar to the latter could not be obtained from the nickel complex of l-(2-carboxyphenyl)-3,5-diphenylformazan but nickel complexes of this type were obtained from both l-(2-hydroxyphenyl)- (169 X = O, R = CN R = Ph) and l-(2-carboxyphenyl)- (169 X = C02 R = CN R = Ph) 3-cyano-5-phenylformazans. In all three cases a considerable shade change occurred on going from the three-coordinate complex to the pyridine adduct. 

The 1,5-diphenyl and 1,3,5-triphenyl derivatives were discovered almost simultaneously by H. von Pechmann [38] and E. Bamberger [39] in 1892. Interest in those compounds was renewed in 1939 when G. Lakon [40] and R. Kuhn and D. Jerchel [41] found that colorless tetrazolium salts were very sensitive to biological reduction processes and were converted to deeply colored formazans ... 

A tetrazolium salt (MTT) 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide is able to enter cells and therefore assay levels of superoxide, without disrupting the cell with DMSO, forming the insoluble formazan product (Slater et al., 1963). Like the NBT test, MTT reduction is not specific for superoxide. 

The present work showed, in perfect agreement with Harries, that on ozonizing sugar alcohols in an aqueous solution, they begin to oxidize and aldoses arise in the course of the oxidation process. For instance, n-mannose was prepared from ozone-oxidized D-mannitol with the aid of the formazan reaction, n-mannose was then identified as D-manno-V,V -diphenyl formazan (8). 

To an aqueous solution of mannitol, ozonized for 7 to 14 hours, phenylhydrazine was added. When the solution was kept in the refrigerator overnight, mannose phenyl-hydra zone separated. On coupling it in pyridine solution with an ice cold solution of diazotized aniline, n-manno-AT AT -diphenyl formazan, crystallizing in brownish red needles, was obtained. 

The EpiOcular model uses normal human-derived epidermal keratinocytes, which form a stratified squamous epithelium morphologically similar to that found in the cornea [36]. The main endpoint evaluated is cell viability measured by dehydrogenase conversion of the vital dye MTT (3-(4,5-Dimethyl-2-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide, Thiazolyl blue EINECS number 206-069-5, CAS number 298-93-1), into a blue formazan salt that is quantitatively measured after extraction from tissues. Two different protocols exist, the EpiOcular ET50 mainly developed for the testing of surfactants and surfactant-based mixtures, and the EpiOcular Eye Irritation Test (EIT) developed for a variety of chemistries. 

Fig. 11.— Lower Curve Mutarotation of n-Galacturonic Acid Phenylhydrazone (pyridine-ethanol, 1 1 by vol.) Upper Curve n-Galacturonic Acid Af.AT -Diphenyl-formazan Formation.

In the model reaction carried out with this compound, it was found that, in pyridine solution, the chelate N —> H completely inhibited formazan reaction, which indicates that, in n-glucose phenylosazone, similar chelation may be responsible for the failure to form a formazan. On replacing the pyridine with alkaline ethanol (often used to catalyze the formazan reaction), the chelate ring was loosened and coupling occurred to give A, A -diphenyl-C-(2-quinolyl)formazan. 

The structure of o-glucosazone formazan is also proved by the synthesis starting from D-glucosone l-(i T -phenyl)hydrazone. Coupling this with diazotized aniline in cold pyridine yields n-glucosone formazan [N,N - diphenyl - C - (d - arabino - tetrahydroxypentanoyl) formazan] as red needles. Condensation of this compound with phenylhydrazine leads to... 

This is now confirmed by the formazan reaction. From ozone-oxidized D-mannitol, n-mannose can be isolated in the form of its iV,iV -diphenyl-formazan. Applying this reaction to ozone-oxidized polysaccharides (for example, cellulose or starch), their bright-red formazans are obtained. ... 

Formazans, acetylated, condensation with phenylhydrazine, 132 action of light on, 109 diphenyl-, of aldohexoses, pentaace-tates of, 110 of sugars, 109, 110 formation of, 106 for identification of aldoses, 113 metal complexes of, 108 structure of, 107 of sugars, oxidation of, 116... 

Zu diesem Reaktionstyp gehort auch die Cyclisierung des Phenylhydrazons von N,N -Diphenyl-C-oxalyl-formazan [Bd. X/3, S. 684 (1965)]. 

Colorimetric MTT (tetrazolium) assay (Mosmann 1983) was used to quantify living cells. In short, yellow MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) is reduced to purple colored formazan in the mitochondria of living cells. The absorbance of the colored solution is analysed using a spectrophotometer allowing for quantification of living cells. 

Finally, in strongly alkaline solution formazans containing removable substituents such as COOH, COCH3, and COCOOH in position 3 can couple with a third diazonium component, giving the so-called 3-(phenylazo)form-azans for instance, l,5-diphenyl-3-(phenylazo)formazan, C6H5NH—N=C-(N=NC6H5)2, is obtained as end-product of complete coupling of acetone,344 acetaldehyde,344 351 354 pyruvic acid,344 351 acetoacetic acid,344 352 malonic acid,343 or acetonedicarboxylic acid,343 etc. 

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