Iodoarenes cross-coupling

Carbonylative cross-coupling of iodoarenes and aryl triflates with g< ///-fluorovinyltributylstannane takes place smoothly in a standard system, with triflate substrates requiring the addition of tetrabutylammonium iodide (Equation (4)). ... 

Besides, iodoarenes aryliodonium salts were used as electrophilic coupling partners in the synthesis of ynones. The carbonylative cross-coupling can be run in aqueous DME in the presence of Pd(OAc)2 and Gul as co-catalyst and NaHG03 as a base at 30 °G. ... 

The cross-coupling reaction of tris(2-ethoxyethenyl)borane (37) [96] or 2-(l-ethoxy-1-alken-2-yl)-l,3,2-benzodioxaboroles (38) with iodoarenes produces styryl ethers in high yields in the presence of Pd(PPh3)4 and powdered NaOH suspended in THF (Scheme 2-37) [97, 98]. Since 37 and 38 have a tendency to undergo base-induced decomposition on prolonged heating, it is desirable to use an iodoarene derivative as a substrate or an excess... 

The mechanism of the copper-mediated cross-coupling of iodoarenes and perfluoroalkyl iodides is supposed to be similar to that of related reactions involving the interaction of halogenoarenes with cuprous salts of organic nucleophilic anions (for example CuCN) [55] (Scheme 2.122). First a solvated perfluoroalkyl copper(I) complex is formed. This then coordinates to the iodoarene followed by exchange of ligands [56]. Several electron-transfer steps are probably involved in this process. 

Interesting applications of the Suzuki coupling protocol are the synthesis of ohgoarylenes with precise length and defined functional groups at both termini of the chain as well as the preparation of unsymmetrical biaryl ketones by the Pd-catalyzed cross-coupling reactions of arylboronic acids with iodoarenes (see Scheme 33). 

Equation 16 Cross-coupling of sulfinyl esters and iodoarenes with Pd(0) [105]... 

Closely related to Heck coupling, the Suzuki cross-coupling reaction (the coupling reaction of a halogenoarene with an arylboronic acid or ester) [218] has also been successfully performed in ionic liquids. Welton et al. used Pd(PPh3)4 as catalyst in [BMIM][BF4] to convert bromo- and iodoarenes vnth phenylboronic acid... 

On the other hand, even the recently prepared Herrmann-Beller catalystf still requires higher temperatures for efficient coupling rates of the Heck reaction. Interestingly, the complexation of chloroarenes with the Cr(CO)3 fragment activates the arene-chlorine bond considerably toward the oxidative addition. Thus, Cr(CO)3 complexed chloroarenes react about 15 times faster than iodoarenes in Pd-catalyzed cross-couphng reactions under mild conditions, in particular in Pd/Cu-catalyzed cross-couplings with terminal acetylenes in refluxing THF and/or tertiary amines (Scheme 36). ... 

An analogous 5-exo-dig carbopalladation, performed on an iodoarene with an ortho-alkynylamino substituent in the presence of hexabutyldistannane, produces an alkenyl-stannane, which undergoes a second cyclization by intramolecular Stille cross-coupling with the second o-iodoaniline moiety in the molecule. The hnal product, though, arises by double bond migration (Scheme 25, Eq. 1). Alternatively, a 1,1-disubstituted aUcene... 

For cross-coupling reactions between iodoarenes and stoichiometric amounts of copper acetylides in the absence of palladium compounds, see (a) Castro, C.E. and Stephens, R.D. (1963) J. Org. Chem., 28, 2163 ... 

Protiodesilylation of the starting material is occasionally encountered in the coupling reactions of arylsilanes with a nucleophihc promoter. This side-reaction can be suppressed by the use of a stoichiometric amount of a copper(I) salt to promote the cross-coupling of arylsilyl ethers with iodoarenes (Scheme 7.36) [63]. The preferred salt is CuOCgFj, generated in situ by mixing Cul and NaOC Fj, to effectively promote this reaction. Unhke other arylsilyl ether cross-couphng reactions wherein a trialkoxysilane is used, the mono-methoxysilane reacted much more efficiently than either the di- or trimethoxysilane. Despite the harsh conditions used, this is an impressive fluoride- and paUadium-ffee reaction. 

The cross-coupling between sp and sp carbon atoms was first discovered in 1963 by Stephens and Castro [1]. Their seminal report described the formation of an internal acetylene from a Cu(I) acetyHde and a phenyl or vinyl haHde (Scheme 9.1). In the original procedure, a variety of substituted tolanes were prepared in 75-99% yield by heating p- or o-substituted iodoarenes with cuprous phenylacetyUde in pyridine. 

Scheme 9.28 The Stille cross-coupling of alkynyltin 82 with the iodoarene 83 using the iminophosphine-ligated Pd catalyst 81 [247].

Ligand-free systems have also been developed. For example, in 2010, Yong and Teo [78] reported the cross-coupling of alkyl amines and aryl iodides under ligand-free copper(I) iodide-catalyzed conditions. The reaction scope was quite good, and very good yields could be obtained, using both iodoarenes and bromoarenes and primary and secondary amines. This protocol in fact is an excellent... 

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