Aryl iodonium salts

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

See Glaser, R. Horan, C.J. Nelson, E.D. Hall, M.K. J. Org. Chem., 1992,57, 215 for the influence of neighboring group interactions on the electronic stmcture of diazonium ions. Aryl iodonium salts Ar2l also undergo substitutions by this mechanism (and by a free-radical mechanism). 

Efficient homocoupling of the aryl iodonium salt 827 using Zn is catalyzed by Pd(acac)2[708], Homocoupling of the arylsulfonyl chloride 828 as a pseudohalide takes place in the presence of 2 equiv. of Ti tetraisopropoxide[709]. 

Electron transfer to the xanthenes, particularly reduction with amines, has been used for a number of years to initiate acrylate polymerization. A typical system is that reported to form volume holograms—lithium or zinc acrylate, triethanolamine and Eosin, Erythrosin, or Rose Bengal [290], Similar mixtures are used to form printing plates photoreducible dye, phenylac-ridine, and acrylate monomer [292], A recent patent application discloses aryl iodonium salts, Rose Bengal, and oxidizable triazines such as 2-methyl-4,6-bis(trichloromethyl)-s-triazine to polymerize acrylates [292],... 

Tributylstannanes have also been used in the synthesis of alkynyl(aryl)iodonium salts, including 1,3-diynyl derivatives373 and the parent member of the family, HC=CIPh+TfO, which was characterized by X-ray structure analysis.374 The bisphenyliodonium triflate reagent 152 [Eq. (4.110)]372 and analogs375 were synthesized in a similar way. Alkynyltrimethylsilanes may also serve as similar useful starting materials.376,377 X-ray characterization of a variety of alkynyl(aryl)iodonium ion has been reported.332... 

Alkynyl(aryl)iodonium salts where aryl was the o-carboxyphenyl group were obtained from silylalkynes and o-iodosobenzoic acid [139]. It is noted that the first alkynyl iodonium salts were obtained in low yield from terminal alkynes. This approach was perfected recently, so that a range of substrates upon reaction with p-MeC6H4IO in aqueous HBF4, with catalysis by HgO, afforded alkynyl (tolyl)iodonium salts [140]. 

The relatively unstable / -oxoalkyl(aryl)iodonium salts 46 can be generated by a low temperature reaction of silyl enol ethers with reagent 45 (Scheme 21) [40]. 

Recent progress on the use of hypervalent iodine reagents for the construction of carbon-het-eroatom (N, O, P, S, Se, Te, X) bonds is reviewed. Reactions of aryl-A3-iodanes with organic substrates are considered first and are loosely organized by functional group, separate sections being devoted to carbon-azide and carbon-fluorine bond formation. Arylations and alkenyla-tions of nucleophilic species with diaryliodonium and alkenyl(aryl)iodonium salts, and a variety of transformations of alkynyl(aryl)iodonium salts with heteroatom nucleophiles are then detailed. Finally, the use of sulfonyliminoiodanes as aziridination and amidation reagents, and reactions of iodonium enolates formally derived from monoketones are summarized. 

Alkenylations of heteroatom nucleophiles with alkenyl(aryl)iodonium salts occur by a variety of mechanisms, including SN1, SN2, alkylidenecarbene, and addition-elimination pathways [ 126,127]. Reactions that occur with retention of configuration at vinylic carbon are sometimes attributed to a ligand-coupling... 

Vinyl(aryl)iodonium salts of assigned stereochemistry Ri IPh, A C=C R2/ ... 

Vinyl(aryl)iodonium salts with cyclic vinyl ligands... 

Alkenyl(aryl)iodonium salts 4 are similarly efficacious for the alkenylation of nucleophiles. Such reactions proceed by various mechanisms, including addition-elimination, -elimination, vinylic S 1 and S 2, and ligandcoupling (LC) pathways (89RHA92, 95MI3, OOJOM494, 00RCR105, 02ACR12). 

Aryl iodonium salts At2I also undergo substitutions by this mechanism (and by a free-radical mechanism). 

A mild method for the A-arylation of both aromatic amines and cyclic secondary aliphatic amines using aryl iodonium salts was reported by Kang and coworkers359. 

FIGURE 21. iV-Arylation using aryl iodonium salts... 

Mixed iodonium salts. Alkenyl aryl iodonium salts can be obtained by reaction of... 

Vinyl(aryl)iodonium salts are good electrophiles carrying an excellent nucleofuge,... 

The first stable class of alkynyl(aryl)iodonium salts were the tosylates, 9, prepared by the interaction of HTIB (5), with terminal alkynes in refluxing chloroform [Eq. (1)] [11-13]. Unfortunately, this method suffers from lack of generality, separation problems from the concomitantly formed alkene salt, 8, and low product yields of 9. 

Alkenyl and aryl iodonium salts have also been coupled with terminal alkynes. The reaction of (E)-[P-(trifluoromethanesulfonyloxy)-... 

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