Azobenzene diazonium salt

A similar template-directed approach was employed (Figure 31) by Anderson et al. [48] to self-assemble azo-dye [2]rotaxanes. The azobenzene diazonium salt 98 is bound by a-cyclodextrin 99 and also by / -cyclodextrin 100 in H20 with pseudorotaxane geometries. Reaction of the terminal diazonium functions with / -naphthol 101 affords the purple [2]rotaxanes 102 and 103 in yields of 12 and 15%, respectively. These two [2]rotaxanes were characterized by electrospray mass spectrometry which revealed peaks corresponding to the loss of all four sodium cations in both cases. By irradiating some of the protons of the dumbbellshaped components of these [2]rotaxanes, enhancement of the resonances of some of the cyclodextrin protons could be observed as a result of an intercomponent... 

The most noteworthy reaction of azo-compounds is their behaviour on reduction. Prolonged reduction first saturates the azo group, giving the hydrazo derivative (C NH-NH C), and then breaks the NH NH linkage, with the formation of two primary amine molecules. If method (1) has been employed to prepare the azo-compound, these two primary amines will therefore be respectively (a) the original amine from which the diazonium salt was prepared, and (6) the amino derivative of the amine or phenol with which the diazonium salt was coupled. For example, amino-azobenzene on complete reduction gives one equivalent of aniline, and one of p-phenylene diamine, NHaCeH NH benzene-azo-2-naphthoI similarly gives one equivalent of aniline and one of... 

The hydroxyphenylbenzotriazole structure was constructed by a coupling of the diazonium salt of o-nitroaniline with 4-ethyl-phenol, followed by reduction of the nitro-azobenzene to the benzotriazole with zinc powder and NaOH. After blocking of the phenol by acetylation, bromination and dehydrobromination were performed as described earlier, and treatment with aqueous NaOH... 

Figure 13-35 illustrates the mechanism for the formation of p-hydroxyazoben-zene beginning with the reaction of benzenediazonium chloride with an aromatic system activated by an -OH. The mechanism for the reaction with an amine is similar. Figure 13-36 illustrates the reaction of a diazonium salt with an amine. The product of the reaction in Figure 13-36 is p-(dimethylamino) azobenzene. 

Perhaps the first observation of this reaction was made in connection with by-product formation of the Sandmeyer reaction in which a diazonium salt is treated with cuprous complexes to afford some azobenzene [15, 16],... 

Azobenzenes 5 were synthesized by coupling of the dialkyl aniline derivative 2 with 4-nitro- or 4-methyl-sulfonylbenzene diazonium salt (Figure 3). Vinylidine compound 6 was prepared by Knoevenagel condensation of the corresponding aldehydes with malononitrile (Figure 4). 

Azobenzene, 340/13/ 6.5 azoformamide, 260/194/925 diketene, 125/140/— 4-nitroisopropylbenzene, 250/ > 182/ 830 4-nitrophenol, 280/ > 199/ 1,030 4-nitro-sophenol, 120/ 23/ 5. It is concluded that the first and last compounds are of relatively low hazard [1]. Improved equipment has provided more accurate and detailed results for a further 7 compounds and has shown the effect of variations in the initial stage of decomposition on the final pressure attained, and of the increase in pressure causing a reduction in the rate of pressure rise. At 0.2 g/cm3 loadings, comparable results are — A diazonium salt, 112/ 200/ 66 azoisobutyronitrile, 80/ 130/ 8,800 1,3-diphenyl-triazene, 140/ 95/ 420 2-nitrobenzaldehyde, 200/ 945/ 8,700 3-nitrobenzaldehyde, 190/ 830/ 4,100, 4-nitrobenzaldehyde, 200/ 960/ 4,700. Solids which deflagrate give substantially higher rates of pressure rise because the rate of pressure rise is not depressed by increase in pressure, e.g. ammonium dichromate, 227/ 510/ 68,000 [2]. 

H Chemical shifts of azobenzene-like compounds,8-26 ortho-, ortho -dihydroxyazopyrazole27 and diazonium salts coupling products with guaiacol,28 5-aminopyrazole,29 2-phenyl-5-oxazolone,30 3-(4-methoxyphenyl)-1 -oxo- 1H,5H-pyrido[l,2-a]benzimidazole,31 2 - ortho, meta, paru-aminophenyl)oxazolo-... 

Table 9 gives the 13C chemical shifts of the compounds77 (3—40) listed in Table 5. Depending on the nature and orientation of the substituents in the dyes, different conformers, resultant from inner rotation around the C-N bonds, could be identified. The 13C chemical shifts of azobenzene-like compounds and diazonium salts coupling products with heterocycles are reported in Refs. 9, 18, 25, 26, 36, 39, 48, 78-87. The 13C chemical shifts of dyes derived from 3-methyl-l-phenylpyrazol-5-one (of type 78 Table 10),88 pyridone (81),39 and acetoacetanilide (82)65 existing completely in hydrazone forms were assigned.

Aldehyde synthesis. The reagent reacts with an alkyl- or arylmagnesium bromide to give a p-dimethylaminophenylcarbinol (1). This is easily cleaved by diazonium salts (diazotized sulfanilic acid was used because 3, Ar = p-H03SC6H4-, methyl orange is easy to eliminate). The products are the aldehyde (2) and an azobenzene... 

Although simple azobenzenes do not usually undergo [4 + 2] cycloadditions,4145 Ahern, Gokel, and co-workers have found that arenediazo-cyanides are effective dienophiles.46 These compounds are prepared by addition of potassium cyanide to diazonium salts in the presence of 18-crown-6 [Eq. (17)]. 

When diazonium salts react in the absence of free acid with amines and phenols, derivatives of azobenzene are formed. As these contain trivalent nitrogen atoms only, it is assumed that in neutral or alkaline solutions the diazonium hydroxides rearrange to diazo hydroxides,... 

The dyes of this class are derived from aromatic azo compounds, such as azobenzene, CeHs—N = N—CeHs. They are prepared by treating a diazonium salt with an amine or a phenol. Thus, if a solution of m-phenylene diamine is added to a dilute solution of benzene-diazonium chloride, the hydrochloride of diamino-azobenzene, which is the dye chrysoidine, is formed —... 

Two of the three possible isomers (94-96) are known. The l,T-isomer (94) was prepared (Scheme 36) by treatment of o,o -azobenzene bis-diazonium salt with sulfur dioxide (67JA2643). Recent attempts to pre-... 

Azobenzene diazonium Fast Garnet GBC sulfate salt Fast black K salt... 

First (R)-3-hydtoxy-l-phenyl pyrrolidine [(R)-HPP] reacted with 4-cyano aniline via coupling to form diazonium salt, (R)-3-hydroxy-l-(4-cyano-4-azobenzEne) pyrrolidine [(R)-HAP-C]. The salt as an intermediate was allowed to react with methaayloyl chloride to synthesize novel optically active monomer (R)-MAP-C as shown in Table 1... 

Both diazonium salts and iodonium salts can be effectively used as arylating agents. The aryl group is transferred either heterolyt-ically or homolytically, depending on the choice of salt and reaction conditions. In acid solution diazonium salts decompose relatively cleanly to give products consistent with a polar mechanism. In basic solution the product is a complex mixture resulting from free radical intermediates (6). When either benzenediazonium chloride or fluoborate is decomposed in acidic methanol, the major product, formed in 93% yield, is anisole, and less than 1% biphenyl is isolated. In the same solvent with an acetate buffer, the product contains 85-90% benzene, 4.5% biphenyl, 0.6% azobenzene, some anisole, and 80-90 mole % formaldehyde per mole of diazonium salt decomposed (7). 

Diethylamine acetate Pyridinium salt Tetramethylammonium acetate. Tetraethyl-ammonium -, Tetra-butylammonium -Piperidinium acetate Isoxazolium salts Trialkyloxonium salt Amidinium salts Ketenimines Hy dr azobenzene Diazo compounds Diazomethane, Phenyl-diazomethane K-methyldiazotate Hexamethylenetetramine Azo compds.. Azobenzene Azodicarboxamide ROOC N N COOR Azodiisobutyronitri le Triazenes Azidinium salts p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazotized... 

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