Aryldiazonium salts

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). 

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. 

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... 

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... 

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). 

The reaction between zwitterion 74 and aryldiazonium salt at room temperature provides the fluoroborate salt 75. Upon treatment with a base the salt 75 undergoes a valence bond isomerization to yield triazolo-pyridazine 76 (Scheme 2) <2000CC1785>. 

Modified CNTs feature various spectral changes depending on the methods and the location of modifications. These changes include variations in band frequencies, width, and intensities. For example, aryldiazonium salts [139] were used to modify individual sodium dodecyl sulphate (SDS) coated SWNTs with aryl group. The Raman spectrum of functionalized (SDS-free) SWNTs shows a disorder mode much higher than pristine SWNT the radial breathing modes are nearly unobservable. 

Aryldiazonium salts are reduced to the benzene derivatives in good yields (Eq. 339).563... 

Aryl aldehydes, alkane reduction, 71-72 Aryldiazonium salts, reduction of, 104 Aryl halides and triflates, reduction reaction, 32 Aryl ketone, allylation,... 

Conventional aryldiazonium salt chemistry on 4-aminoindole provides 4-iodo-l-(4-toluenesulfonyl)indole (13), 4-iodoindole (14), and l-(fm-butyldimethylsilyl)-4-iodoindole (15) in excellent yields as shown [25, 26],... 

The synthesis of some new mesoionic triazoloquinazoles 485 has been reported by Abbott et al. <2002T3185>. These authors reported that treatment of 484 with an aryldiazonium salt followed by reaction with acetic anhydride in pyridine results in a ring closure to 485. The first step is an azo-coupling on the ring nitrogen atom, whereas the second part of the transformation is the removal of a molecule of water. 

P-Phosphorins having a phenyl residue at C-4 [e.g. (188)] are arylated in the aryl ring by aryldiazonium salts.165 The ethoxycarbonyl group of the A5-phosphorin (189) can be hydrolysed, transesterified, or reduced without destroying the ring system.166... 

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

There are reasons to explain the catalytic activity of copper(ll) in terms of cation-radical mechanism. This mechanism is confirmed by the unusual direction of Meerwein reaction in some cases, for example, when the replacement of halogen by an aryl radical occurs in the reaction of halo-styrenes with aryldiazonium salts (Obushak et al. 1991). A cation-radical in the system [olefin-Cu(II)] has been detected by UV spectroscopy (Obushak et al. 1991). In the cases of cis isomers of benzylidenacetone (Allard and Levisalles 1972) and maleic esters (Isaev et al. 1972), the unreacted... 

Analogous consideration of aryldiazonium salts and sulfur dioxide reaction with a-nitro olefins in the presence of cupric chloride gave rise to a conclusion that the process also includes the electron-transfer step and develops according to anion-radical mechanism (Bilaya et al. 2004). The reaction eventually leads to the formation of p-arylsulfonyl a-nitroethanes. 

Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group. Coupling reaction of aryldiazonium salts with phenols or arylamines give rise to the formation of azo dyes. 

The addition of aryl radicals, generated by chemical reduction of aryldiazonium salts, onto arenes in the Gomberg-Hey reaction is well established [163]. The addition of these radicals to alkenes in the Meerwein reaction is also well known [164], Aryl o-radicals generated by electrochemical reduction of aryl halides take part in similar reactions. Good yields of the products are obtained when the intermediate phenyl radical can react in an intramolecular manner. The addition step is then fast and competes successfully with further electron transfer to form the phenyl car-banion, followed by protonation. 

Imidazole-2-diazonium fluoroborate is an irreversible blocker of the phencyclidine binding site of the nicotinic cholinergic receptor, and it is only effective when the receptor is in a desensitized state, at variance with other aryldiazonium salts (85MI1). 

Another approach to synthesizing pyrazolo[4,3-e]-l,2,4-triazines is by coupling ethoxycarbonylpyrazolones with aryldiazonium salts and subsequently cyclizing the resulting hydrazones e.g., the formation of 146 from 144 via 145 (76MI1). 

Other reactions with electrophiles that have been recorded are those with aryldiazonium salts, with p-dimethylaminobenzaldehyde, and with alkyl halides. 

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