Aryldiazonium compounds

In this connection, it is remarkable that in 1893 Noelting and MicheP produced, albeit unknowingly, arylpentazoles (2) while generating aryl azides (3) from aryldiazonium compounds and sodium azide. 

Nitration via diazotisation has been extensively used for the synthesis of isomeric dinitronaphthalenes. Ward and co-workers used nitration via diazotisation to prepare 3,3, 4,4 -tetranitrobiphenyl from 3,3 -dinitrobenzidine, and 3,4,5-trinitrotoluene from 3,5-dinitro-4-toluidine. Ward and Hardy " prepared 1,4,6-trinitronaphthalene from 4,7-dinitro-1-naphthylamine. Korner and Contardi used the nitrate salts of aryldiazonium compounds for the synthesis of polynitro derivatives of benzene " and toluene. " " Accordingly,... 

Scheme 1.27 Electrochemical modification of SWCNTs with aryldiazonium compounds (a) reductive coupling of preformed p-nitro-phenyldiazonium salts to SWCNTs and (b) anodic oxidation with in situ-generated dia-...

However, several inherent drawbacks limit the utility of aryldiazonium salts as photoinitiators in a number of practical applications for epoxy curing. Nitrogen evolution during photolysis of the initiator causes bubbles and pinholes in coatings. Other problems arise from the poor thermal stability of aryldiazonium compounds and from their inherent sensitivity to moisture. The addition of stabilizing additives such as nitriles amides sulfoxides and poly(vinylpyrrolidone) has proven effective in extending the solution stability of aryldiazonium salt/epoxy mixtures. 

Many phenols are best prepared by boiling aryldiazonium compounds with water. Excess nitrous acid from the diazotization is first destroyed by addition of solid urea, Some substituted diazonium compounds are hydrolyzed with difficulty. Refluxing with aqueous sulfuric acid, copper sulfate, or sodium sulfatesolutions is usually recommended. 

Since 1910 the method of Bart has been modified by a number of investigators, Bart, himself, being the first to improve the reaction. He found that coupling of aryldiazonium compounds with alkali arsenites is catalyzed by copper salts and by silver or copper powder. In a later patent the use of metallic catalysts, copper, nickel, or cobalt, as well as their salts is said to facilitate the removal of diazo nitrogen at low temperatures and to obviate the formation of by-products. Though many have since observed that the coupling reaction is speeded by the use of the above catalysts, no systematic study has been made to determine the effect of such catalysts on the final yield. 

The third type of composition is exemplified acrylate- and methacrylate-ester derivatives of epoxy resins combined with a photoinitiator 1. Epo prepolymers (e. g., glycidyl methacrylate-allyl glycidyl ether copolymers or Ciba ECN 1299) combined with a photosensitive aryldiazonium compound (e.g.,... 

The third type of composition is exemplified by acrylate- and methacrylate-ester derivatives of epoxy resins combined with a photoinitiator 1. Epoxy prepolymers (e. g., glycidyl methacrylate-allyl glycidyl ether copolymers or Ciba ECN 1299) combined with a photosensitive aryldiazonium compound (e.g., -nitrobenzenediazonium hexaflourophosphate) (38,39) 2. Epoxy prepolymers (e.g., a diglycidyl ether of disphenol A-(3,4-epoxycyclohexyl)-methyl-3,4-epoxycyclohex-anecarboxylate-alkyl glycidyl ether mixture) combined with a photosensitive aryldiazonium compound (e.g., -chlorobenzenediazonium hexaflourophosphate) and l-methyl-2-pyrrolidone gelation inhibitor (40) ... 

Isocyanides readily undergo cycloaddition reactions, and these are very valuable in the formation of heterocyclic rings. Reaction of j5-nitrostyrene with an alkyl isocyanide gives a hydroxy indole (146). Reaction proceeds even more readily between tosylmethyl isocyanide (147), in which the methylene is activated, and aryldiazonium compounds. With ketenes, isocyanides give imino lactones. However, with r-butylcyanoketene, the reaction follows a different pathway involving the carbonyl bond of the ketene, to yield 148. A [1 + 3] cycloaddition of an isocyanide to a 1,3-dipole has been used to prepare azetidines. The method has been used for synthesis of a number of azetidines . 

Several methods have been proposed based on the decomposition of diazonium salts. The volume of nitrogen can be measured after treating aryldiazonium compounds with copper(i) chloride , potassium iodide , or titanium(iii) chloride . Otherwise, the excess catalyst can be determined, as in the case of titanium(m) chloride , or chromium(ii) chloride . The diazonium compound strongly heated with hydriodic acid yields iodine which can be titrated . 

Although numerous complexes of macrocyclic ethers and cryptates exist, one of the more interesting and unusual examples is the complex between appropriately sized crown ethers and aryldiazonium compounds [14]. The insertion complex is formulated in equation 15.3 and the evidence for this structure has been reported [14]. Thus far, only 1 1 complexes have been isolated [15, 16]. 

In the preparation of bromo compounds by the Sandmeyer reaction, the amine is generally diazotised in sulphuric acid solution (or in hydrobromic acid solution), and the resulting aryldiazonium sulphate (or bromide) is treated with a solution of cuprous bromide in excess of hydrobromic acid the addition... 

The reaction is very common in pyrazolone chemistry. Since alkoxypyrazoles and tautomerizable pyrazolones undergo this reaction and 3-pyrazolin-5-ones, like antipyrine, do not, it is assumed that the reaction takes place at C-4 of the OH tautomer. Pyrazolone diazo coupling is an important industrial reaction since the resulting azo derivatives are used as dyestuffs. For instance, tartrazine (Section 4.04.4.1.3) has been prepared this way. 3,5-Pyrazolidinediones react with aryldiazonium salts resulting in the introduction of a 4-arylazo group. As has been described in Section 4.04.2.1.4(v), diazonium salts couple in the 3-position with indazole to give azo compounds. 

Owing to their particular interest two individual reactions will now be discussed separately. The reaction of methoxycarbonylhydrazine and 3-bromo-2,4-pentanedione affords, in addition to the expected pyrazole (608), a pyrazolium salt (609), the structure of which was established by X-ray crystallography (74TL1987). Aryldiazonium salts have been used instead of arylhydrazines in the synthesis of pyrazolines (610) and pyrazoles (611) (82JOC81). These compounds are formed by free radical decomposition of diazonium salts by titanium(n) chloride in the presence of a,/3-ethylenic ketones. 

The express method of phenolic compounds determination was designed. It is based on heterogeneous azo-coupling reaction of phenols, which different extracts of fresh raw material contain, with aryldiazonium salts grafted on the silica surface. We can carry out phenols analysis on-site, as formation of immobilized azocompounds leads to a drastic change in the sorbent s color. Thus, we pui pose a new method, that allows to indicate herb phenols in aqueous and non-aqueous medias and to compare it with a well-known Folin-Ciocalteau method. 

Reaction of glycosylmethylamines with aryldiazonium salts gives a class of compounds which, by acid catalysis or unknown factors of enzymic catalysis, generate glycosylmethyldiazonium ions. These, in turn, lose nitrogen, to yield highly electrophilic carbenium ions, as illustrated for the ) -d-galactosyl derivative 38 (see Scheme 8). 

As mentioned in the discussion of the reaction mechanism for this transformation, the active species is a dicoordinate Pd(0) complex, and it is unclear whether an associative or a dissociative process is operative for oxidative addition. In this context, different NHC complexes containing only one carbene ligand have been tested in the Mizoroki-Heck reaction. The most successful are those prepared by Beller, which were able to perform the Mizoroki-Heck reaction of non-activated aryl chlorides with moderate to good yields in ionic liquids (Scheme 6.13). The same compounds have also been applied to the Mizoroki-Heck reaction of aryldiazonium... 

Since sulphones 204 are easily available compounds one would expect that they could be used as starting materials for the preparation of sulphoxides via the selective removal of one oxygen atom from the sulphonyl group (equation 112). Up to now, there is only one example reported of a direct reduction of a sulphone to a sulphoxide. The bicyclic dideuterio sulphone 205 after 24 h treatment with three-fold excess of diisobutyl aluminium hydride in boiling dichloromethane gave the corresponding sulphoxide 206 in 36% yield (equation 113). A two-step procedure for the selective reduction of sulphones to sulphoxides, which involves an initial reaction of sulphone 204 with aryldiazonium tetrafluoroborate 207 to form aryloxysulphoxonium salt 208 and its subsequent reduction (equation 114), was alluded to by Shimagaki and coworkers and... 

Meerwein reaction consists of condensation of ethylenic compounds with aryldiazonium salts in the presence of cupric and cuprous salts ... 

Ganushchak et al. (1972, 1984) proposed to perform the Meerwein chloroarylation of ethylenic compounds using the preliminarily prepared aryldiazonium tetrachlorocuprates. They found that methyl, ethyl, butyl acrylate, methyl methacrylate, and acrylonitrile in the polar solvent reacted with tetrachlorocuprate. Chloroarylation products were obtained with better yields than when using the traditional Meerwein reaction conditions. 

Insertion of mono- or bis(aryldiazonium) cations into the Re—bonds of the hydride complexes [ReH(CO)5 (PR3)J (PR3 = P(OEt)3, PPh(OEt)2, PPh2(OEt) =1 ) results in the formation of cationic aryldiazene complexes of the compositions [Re(HNNAr)(CO)5 (PR3) ]" or [ Re(CO)5 (PR3) 2(/r-HNNArNNH)] +. " Bifunctional diazene/diazonium derivatives which can be prepared in this way are excellent building blocks for heterobinuclear and heterotrinuclear compounds with bis(aryldiazene) bridging ligands as has been demonstrated for Re-Ru, Re-Os,... 

The great reactivity of ferrocene toward electrophilic reagents prompted an early examination of its behavior with aryldiazonium salts. Azoferrocenes were expected to be formed by analogy to the reaction of phenol and related reactive aromatic compounds. The reactions instead were found to proceed with elimination of nitrogen and the products were arylferrocenes (XXIII). 

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