Aryl iodides coupling

Wang and Scott [189] have described a two-step reaction in which an iodopyrrole is reacted first with hexabutylditin and subsequently with an aryl or heteroaryl halide unfortunately two different catalysts are required. Bates and Parker [190] have carried out the two-step synthesis of a ligand designed to impose a tetrahedral coordination geometry, the product of the initial ditin/aryl iodide coupling reacting further with a heteroaryl halide without change of catalyst (Scheme 4-49). 

Bu,NX(X = Cl, Br) ITBACI, TBABr], solid base Alkenyl and aryl iodides Coupling at rt [100]... 

The highiy oxygenated antifungai/anticancer naturai product ( )-diepoxin o was prepared in the laboratory of P. Wipf. The coupling of the two substituted naphthalene rings was achieved via the Ullmann condensation of a phenolic compound with 1-iodo-8-methoxynaphthalene. The aryl iodide coupling partner was used in excess and the condensation was conducted in refluxing pyridine in the presence of a full equivalent of copper(l)-oxide. 

The vinyl triflate of Kornfeld s ketone has been subjected to Heck reactions with methyl acrylate, methyl methacrylate, and methyl 3-(A-rerr-butoxycarbonyl-A-methyl)amino-2-methylenepropionate leading to a formal synthesis of lysergic acid [257], A similar Heck reaction between l-(phenylsulfonyl)indol-5-yl triflate and dehydroalanine methyl ester was described by this research group [258], Chloropyrazines undergo Heck couplings with both indole and 1-tosylindole, and these reactions are discussed in Chapter 10 (pyrazines) [259], Rajeswaran and Srinivasan described an interesting arylation of bromomethyl indole 240 with arenes [260]. Subsequent desulfurization and hydrolysis furnishes 2-arytmethylindoles 241. Bis-indole 242 was also prepared in this study. Aryl iodides couple with indole under basic conditions to afford 2-arylindoles [261]. 

O/t/20-arylation of benzoic acids is often preferable to ortho-arylation of benzamides if conversion of the amide moiety to other functional groups is desired. However, only a few reports have dealt with the orf/io-functionalization of free benzoic acids due to challenges that involve such transformations. The reactions can be complicated by decarboxylation of the product and the starting material. Despite those difficulties, several methods for direct o/t/io-arylation of benzoic acids have been developed. Yu has shown that arylboronates are effective in arylation of benzoic acids under palladium catalysis [59], The reactions require the presence of palladium acetate catalyst, silver carbonate oxidant, and benzoquinone. Even more interestingly, the procedure is applicable to the arylation of unactivated sp3 C-H bonds in tertiary carboxylic acids such as pivalic acid (Scheme 13) if aryl iodide coupling partner is used. Aryl trifluoroborates can also be used [60],... 

Organozinc-aryl iodide coupling. The method serves for the preparation of unsymmetrical biaryls and o-acylbenzylboronates and thence o-quinodimethanes. ... 

A survey of coupling partners shows this to be a very general method that tolerates several functionaHties and proceeds readily at room temjjerature. Unlike most TBAF-promoted reactions, however, the Z-isomer of the silanol reacts at a much lower rate than the -isomer. In general, electron-deficient aryl iodides couple faster than their electron-rich counterparts. The synthetic potential of this new method of activation is clearly demonstrated in the synthesis of ( )-and (Z)-64. The coupHng reaction occurs cleanly in the presence of a TBS (t-butyldimethylsilyl)-protected alcohol, without any observable deprotection. Thus, not only is the compatibihty with silyl protective groups estabhshed, the concept of employing the silanol moiety as a prosthetic group for controlled carbon-carbon... 

C5-arylation of iV-protected L-histidine could be achieved using microwave irradiation via a Pd-catalyzed process employing pivalic acid and tricyclohexylphosphine (eq 2 ) Other phosphines, such as PPhs and P(2-furyl)3, produced diminished conversions. Moderate yields could be obtained without a ligand (54%), albeit tricyclohexylphosphine was required to maximize product formation. Good functional group tolerance was observed for aryl iodide coupling partners orf/zo-substitution and sensitive groups, such as cyano, nitro, ester, and chloro substrates, were compatible. Aryl bromides could also be employed, albeit with diminished yields (10-18%). 

Aryl iodides couple with aryl aldehydes in the presence of NiBr2(dppe) and Zn to give the corresponding biaryl ketones. The use of a bidentate ligand is critical to the success of this catalytic reaction [86]. 

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