Aryldiazonium preparation

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). 

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. 

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). 

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... 

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. 

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,... 

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 main drawback to this reaction is the toxicity of diazomethane and some of its precursors. One possible alternative is the use of alkyltriazenes as reactive alkylating agents.52 Alkyltriazenes are readily prepared from primary amines and aryldiazonium salts.53 The triazenes, on being protonated by the carboxylic acid, generate a reactive alkylating agent that is equivalent, if not identical, to the alkyldiazonium ions generated from diazoalkanes. 

Several examples of the mesoionic 3-aryl-l,2,3,4-oxatriazole-5-oxide ring system 123 have been prepared by cyclisation of the arylhydrazones 122 these in turn are prepared from aryldiazonium salts and bromonitromethane <99KGS413>. 

Explosive 1-arylpentazoles (551 Ar = Ph, 4-Me2NC6H4, etc.) can be prepared by reaction of aryldiazonium salts with azide anion (85AG515,98JCS(P2)2243). 

Cyclizations of aromatic diazonium salts138 (intramolecular Meerwein arylations) are pieparatively related to atom transfer reactions because a radical cyclization is terminated by the transfer of an atom or group other than hydrogen. However, the two methods are not mechanistically related. In the atom transfer method, the atom that is transferred to the cyclic product always derives from the radical precursor, but in the cyclizations of aryldiazonium salts, die atom or group transferred derives from an added reagent. This means that many different products can be prepared from a single diazonium precursor, but it... 

Three methods are commonly employed for the in situ preparation of organopalladium derivatives (i) direct metallation of an arene or heterocyclic compound with a palladium(II) salt (ii) exchange of the organic group from a main group organometallic to a palladium(II) compound and (iii) oxidative addition of an organic halide, triflate or aryldiazonium salt to palladium(O) or a palladium(O) complex. 

Arylhydrazono derivatives may be prepared from 4-oxo-6,7,8,9-tetrahy-dro-4H- or 9-formyl-4-oxo-1,6,7,8-tetrahydro-4//-pyrido [ 1,2-a]pyrimidine with aryldiazonium salts.307... 

The reaction of compound 90 with imidoyl halides without added base gives the hydrochloride salts of 1,2,4-thiadiazol-5-imines 95. The corresponding free bases can be liberated from the salts 95 with weak bases such as bicarbonate, but these imines are labile and decompose readily to form the W-cyanamide 96 and sulfur. The free base can be treated in situ with a second electrophile, such as an acid chloride, imidoyl chloride, or aryldiazonium salt, affording pentalene derivatives 97-99. It should be noted that the compound 98 cannot be prepared in a one-pot procedure from compound 90 and 2 equiv of imidoyl chloride in the presence of base, in contrast to the corresponding dioxa compound 91 (Scheme 22) <1981BSB89, 1992JHC1317>. 

The most recent modification of Bart s reaction involves the use of aryldiazonium borofluorides in place of the customary diazonium chlorides. Because of their increased stability the diazonium borofluorides were observed to have less tendency to decompose or to form byproducts when allowed to react with sodium arsenite furthermore, the reactions could be carried out at room temperature. The modification appears to be particularly useful in the preparation of p-nitrophenylar-sonic acid, the yield being 79% as compared with 45% by the original method of Bart. When other diazonium borofluorides were used as starting materials the yields were sometimes lower than those reported by the usual Bart procedure, but more often they were as good or slightly... 

The first synthesis of arylboronic esters 209-215 via the coupling of bis(pinacolato)diborane(4) with easily prepared aryldiazonium tetra-fluoroborate salts was reported. The palladium-catalyzed borylation reaction proceeds efficiently under mild reaction conditions in the absence of a base to afford various functionalized arylboronic esters in moderate to high yields (Scheme 34).121... 

JHC859). 8-Arylguanine (and guanosine and GMP) have been similarly prepared from guanine (or guanosine or GMP) and aryldiazonium ions at pH 8.5 or 10.5 in aqueous solution (82JOC448, 82H(18)64> (see Section 7.11.5.2.3). 

Reaction of [Ru(porph)CO] (porph = mew-porphyrin IX dimethyl ester) with NO in benzene yields [Ru(porph)(NO)2], vN0 - 1786 and 1838 cm-1.2589,2590 [Ru(OEP)(CO)py] with NO in MeOH affords [Ru(OEP)(OMe)NO].2572 The aryldiazonium adducts [Ru(porph)(N2Ar)solvent]+ (porph = TPP, Ar = Ph, 4-MeOPh, solvent = acetone porph = TPP, Ar = 4-N02Ph, solvent = EtOH porph = OEP, Ar = 4-N02Ph, solvent = EtOH) have been prepared by reaction of [Ru(porph)(CO)(HOEt)] with ArN2+ in refluxing CH2C12.2618 The stretching vibration vN=N occurs near 1800 cm-1 for these complexes.2618... 

An additional method to prepare 2-aryl benzo[ ]furan was realized by the palladium-catalyzed C-H activation of benzoMfuran with aryldiazonium trifluoroacetate (Equation 95) <1999EJ01357>. 

Halogenated Cinnamic Acids and Esters Thereof, Processes for the Preparation Thereof and Halogenated Aryldiazonium Salts M. Beller etal, US Patent 5,516,932 (May 14, 1996)... 

The structure of the rearranged methoxy-phenol 27 was easily determined by de-methylation with hydrogen iodide to give the hydroquinol 30. Oxidation affords the red 2,3,4,6-tetraphenylquinone 31, identical to the quinone which was first prepared by Kvalnes, 6> by arylating quinone with aryldiazonium salts. 

Aromatic fluorination A new method of aromatic fluorination involves treatment of aryltriazenes, readily prepared from aryldiazonium ions and dialkyl-amines, with 70% hydrogen fluoride in pyridine. The yields of product from this reaction are usually higher than those obtained by the reaction of HF-pyridine with a diazonium ion (6, 285) o-methoxy, iodo-, bromo- and nitro-substituted aryltriazenes generally give unsatisfactory yields. This method may be useful for the synthesis of " F-labeled compounds. 

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