Arylating reagents

Entry Indole reactant Arylation reagent Catalyst Yield (%) Ref. 

In dimethyl sulfoxide (DMSO) the isomer ratios for aryl-de-diazoniation of 4-nitrobenzenediazonium ions demonstrate that the 4-nitrophenyl radical is the arylating reagent (Gloor et al., 1972 see Sec. 8.2). 

Figure 11.5. Representative example of the mechanistic pathway of phase transfer catalysis (PTC). (Z, Z — functional group M = metal Q = chiral catalyst R = alkyl or aryl reagent X = halogen).

Aryl ethers. Unlike other Bi(V) arylaling reagents, this reagent converts phenols into unsymmetrical diaryl ethers (equation 1). Yields are in the range 50-75%. Yields are improved if the phenol is treated first with Bi(C6H5)s and then with TFA. The reagent also converts aryl thiols into mixed diaryl sulfides. 

A rhodium-chiral phosphine complex catalyzes the enantioselective addition of phenylboronic acid to 1-naphthaldehyde to give a chiral diaryl carbinol but with moderate ee (Scheme 13) [39]. When considering the introduction of functionalized aryl groups, arylboronic acid is a promising alternative arylating reagent to diarylzinc compounds. 

Aryl-, as well as heteroaryliodonium salts, belong to the most common, stable, and well investigated class of polyvalent iodine compounds. The preparation and chemistry of aryliodonium salts was extensively covered in several reviews [5,7,9,10]. Diaryliodonium salts have found synthetic application as arylating reagents in reactions with various organic substrates. 

Monoarylation of diamines has been achieved by treatment of excess diamine with an arylating reagent (Scheme 10.19) [82-84]. If the arylation is slow the statistically expected amounts of mono- and diarylated product will usually result. An effective means removing excess diamine will, however, be required the purification of the products. 

Benzanilides also undergo ortho arylation (Eqs. 9 and 10) [16]. For these reactions, aryl triflates as arylation reagents are more effective than aryl bromides. The reaction is also believed to proceed via coordination of amide anion to ArPd(II), because no reaction occurs with secondary amides. 

It should be noted that introduction of a substituent to these substrates at an appropriate position enables the exclusive formation of the mono-arylated product as represented by Eqs. (10) and (12) (see also Scheme 2). The use of a limited amount of arylating reagent is sometimes successful for obtaining mono-arylated product selectively. In the reaction of Eq. (14), the Cp ligand on the ruthenium catalyst is believed to enable selective mono-arylation [19]. 

Apart from the above two major general reaction pathways, there are some further possibilities for instance, [bis(trifluoroacetoxy)iodo]benzene reacts as an ambident electrophile and is attacked by hard nucleophiles at its carbonyl carbon, whereas iodylarenes may react similarly from carbon rather than iodine. Alkynyl iodonium salts are actually tetraphilic electrophiles, whereas iodosylbenzene reacts also as a nucleophile from oxygen. Diaryl iodonium salts serve as arylating reagents, mostly homolytically other iodonium salts transfer groups such as perfluoroalkyl, vinyl, alkynyl or cyano to several nucleophiles in various ways. 

Organo magnesium halides and organo lithium compounds are readily accessible alkylation and arylation reagents. However, they have little practical importance for the preparation of diorgano tellurium derivatives. Tellurium tetrachloride cannot be alkylated or arylated stepwise to give, for instance, diorgano tellurium dihalides, which could... 

Evans et al. [28] reported the H-NMR spectra of a variety of alkyl and aryl reagents in a number of coordinating solvents. These measurements were carried out over a considerable temperature range and, at the lowest temperatures, chemical exchange was on the H-resonance time scale. 

Diaryl sulfamides (201) produced in the condensation of Grignard (primary, tertiary or aryl) and ( -ga-nolithium (primary or aryl) reagents with sulfamylimines (200) can, however, be hydrolyzed in refluxing aqueous pyridine to afford arylamines (202) in good (75-95%) overall yield (Scheme 38). ... 

Because the C-Bi bond to relatively weak ( 46 kJ/mol), aryl Bi(V) compounds have been used extensively as arylation reagents Inorganic arylation reactions have been known since the early 1900s. The elimination of ArX from a Bi(V) starting material is representative of this reaction, shown for a tetraaryl derivative ... 

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