Aryldiazonium ion

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

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

In addition to aryl halides and inflates, aryldiazonium ions can be the source of the electrophilic component in coupling with arylboronic acids139 (entries 4 and 5 in Scheme 8.11). 

The known pentazoles are aryl derivatives which have the structure (3). They are obtained from the reaction of aryldiazonium ions with azide ion (Equation (2)). No alkylpentazoles are known and the reaction of diazomethane with HN3 which gives methyl azide has been shown by N-labelling not to pass through a pentazole intermediate <58HCA1823>. The parent NH-pentazole is unknown. The numbering system shown in (3) will be used in this chapter. 

Other pseudohalides such as aryldiazonium ions (Table 2, entry arylsulfonyl chlorides (Table 2, entry 4)," ... 

The Japp-Klingemann coupling of aryldiazonium ions with enolates and other nucleophilic alkenes provides an alternative route to arylhydrazones. The reaction has most frequently been applied to (Vketoesters, in which deacylation follows coupling and the indolization affords an indole-2-carboxylate ester. 

Aromatic Diazonium Ions. In contrast to alkyldiazonium ions, aryldiazonium ions are well-studied.469 77 They were known as early as 1894. They are isolable as ionic salts with a variety of counterions such as BIT, PF6, SbCl6, SbF6, AsF6-, and C104. They undergo a variety of nucleophilic reactions and an excellent review is available on the subject.478... 

The only example to date of the insertion of an aryldiazonium ion into a metal-hydrogen bond to yield a hydrazido(2-) complex is that shown in Eq. (34) (66, 67). 

Primary aromatic amines react with nitrous acid to give aryldiazonium ions, ArN2+, which are useful intermediates in synthesis of aromatic compounds. The process by which they are formed is called diazotization. The nitrogen in these ions can readily be replaced by various nucleophiles (OH, Cl, Br, I, CN). Diazonium ions couple with reactive aromatics, such as amines or phenols, to form azo compounds, which are useful as dyes. 

Aryldiazonium ions and sodium azide react to form aryl azides. We did not mention this reaction in the discussion of the SN reactions of Ar—N2 (Section 5.4) because it belongs, at least in part, to the 1,3-dipolar cycloadditions. 

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). 

The reaction of aryldiazonium ions with l-(4 -sulfophenyl)-3-methyl-pyrazolium-5-one (7.70) takes place at the 4-position, and the p factor for the effects of substituents in the aryl ring of the diazo ion is 3.29, similar to that for coupling at the 1-position of 2-hydroxynaphthalene-6-sulfuric acid (69CCC3895). For coupling at the 4-position of l-phenyl-2,3-dimeth-ylpyrazolium-5-one (7.71) the corresponding p factor was 3.60 (69CC3905). 

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. 

Treatment of Cs4[Mo4(CO) 2(011)4] with aryldiazonium ions in a water/ether two-phase system gave [ArN NMo(CO)20H]4 (XXIV). Although i nn occurred higher than in the corresponding 7T-C5H5 and... 

The aryldiazonium ion is usually prepared in situ and then immediately combined with a nucleophile to give a substitution product. The mechanisms of the substitution reactions vary greatly with the nucleophile, ranging all across the mechanistic spectrum of organic chemistry. For example, both hypophosphorous acid (H3P02) and I react with diazonium ions by an SrnI mechanism (Chapter 2) to give the reduced arenes or aryl iodides, respectively. 

The nucleophiles H20 and BF4- react with aryldiazonium ions to give phenols and aryl fluorides, respectively. Because neither H2O nor BF4 are oxidiz-able enough to transfer an electron to the aryldiazonium ion, only SN1 mechanisms are reasonable for these reactions. 

Finally, the terminal N of aryldiazonium ions is also electrophilic, and electron-rich aromatic compounds such as phenols and anilines undergo electrophilic... 

Reactions of cyclic and acyclic 1,2,3-triones with phenylhydrazine give rise to mono- and bis-(phenylhydrazones). The central carbonyl group of a vicinal tricarbonyl system is electron-deficient and highly electrophilic,255 which is why treatment with an aryldiazonium ion affords 2-phenylhydrazones. The structure of such bis(phenylhydrazones) as cyclopentane-1,2,3-trione 1,3-bis(phenylhydrazone), dehydroascorbic acid 2,3-bis(phenylhydrazone), and cy-clobutanetetraone l,3-bis(phenylhydrazone) has been studied by UV, IR,1H-, 13C-, and 15N-NMR spectroscopy.265-268 Quantum-mechanical calculations to predict the most stable tautomeric forms of some 1,2- and l,3-bis(phenylhydrazones) revealed that the chelated bis(hydrazone) structure was usually more stable than the azoene-hydrazine structure.269-271 This does not mean that such structures do not exist, for example cyclobutanetetraone l,2,3-tris(phenylhydrazone) exists in a stable phenylazoene-hydrazine structure (see 49 Scheme 8).257-263... 

---