Aryldiazonium

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... 

Arylthio-5-ethyl-4(5)-thiazolone derivatives (164, 165. and 166) have been prepared by treatment of rhodanine (163) with the appropriate aryldiazonium salts (Scheme 86) (395). 

Fluoroaromatics are produced on an industrial scale by diazotization of substituted anilines with sodium nitrite or other nitrosating agents in anhydrous hydrogen fluoride, followed by in situ decomposition (fluorodediazoniation) of the aryldiazonium fluoride (21). The decomposition temperature depends on the stabiHty of the diazonium fluoride (22,23). A significant development was the addition of pyridine (24), tertiary amines (25), and ammonium fluoride (or bifluoride) (26,27) to permit higher decomposition temperatures (>50° C) under atmospheric pressure with minimum hydrogen fluoride loss. 

Another important reduction process is that of aryldiazonium salts with sulfite/bisulfite at controlled pH to produce aryUiydrazines. AryUiydrazines are important intermediates for the preparation of pyrazolones and indoles. 

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. 

Another example is the reaction of aryldiazonium ions with nucleophiles in aqueous solution according to... 

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. 

Arylpentazoles can be prepared by adding an aqueous solution of azide to a mixture of an aryldiazonium chloride, aqueous methanol, and petroleum ether at —40 to —20° with stirring. The pure aryl-pentazole (see Table I) crystallizes from the two-phase reaction mixture the inorganic impurities remain in the aqueous methanol and the organic impurities in the petroleum ether. 

Free carbenes based on 1,2,4-triazole are not as numerous as those based on imidazole (70ZN(B)1421, 95AGE1021, 97JA6668, 98JA9100). The carbene complex 169 (Ar = Ph, p-Tol) is prepared by the [3 + 2] cycloaddition route from [W(CO)j(C+=NC-HCOOEt)]- and aryldiazonium (930M3241). Oxidative decomplexation causes tautomerization of the 1,2,4-triazole ligand, the products being 170 (Ar= Ph, i-Tol). 

Arylhydrazono-6,7,8,9-tetrahydro-4//-pyrido[],2-u]pyrimidin-4-ones 154 were obtained from 6,7,8,9-tetrahydro-4//-pyrido[l,2-u]pyrimidin-4-ones 153 with aryldiazonium chlorides in the presence of NaOAc 3H2O at 0 °C overnight (96JHC799, 99MI12, 00MI22). 

Coordination chemistry of aryldiazonium cations aryldiazcnato (arylazo) complexes of transition metals and the aryldiazenato-nitrosyl analogy. D. Sutton, Chem. Soc. Rev., 1975, 4, 443-470 (89). 

Arenesulphinylation 264 Arenesulphinylethanes, synthesis of 267 2-Arenesulphonyl-3-aryloxaziridines, as oxidizing agents 254 Arenesulphonyl azides, reactions of 641 At-Arenesulphonyliminopyridinium betaines, mass spectra of 160-162 Arenesulphonyl radicals 215, 1091 Aryldiazonium salts, reactions of 280, 281 Aryl(methylsulphinyl)(methylthio)alkenes, synthesis of 614... 

Aryldiazonium-tetrafluoroborate werden durch Natriumboranat in Methanol Oder in waBr. Losung unter Reduktion am endstandigcn Stickstoff-Atom zu Aryl-diazen reduziert, das in ein komplizicrtcs Gemisch zer-fallt5 s. 

From I-Thioaldose Derivatives by Reaction with Aryldiazonium Salts. 183... 

Scheme 19 Aryldiazonium salt reacts spontaneously with H-Si(l 11) to afford modified Si(l 11) surfaces depending from the reaction conditions.

Aiyl diazonium salts can be used coupled with alkenes in a Heck-like reaction (14-20). Other reactive aryl species also couple with aryldiazonium salts in the... 

A mechanism at the Sj 2Ar/Sj l boundary was proposed for the nucleophihc substitution reaction of aryldiazonium ions in water [86],... 

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