Aryl iodonium

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). 

Cyclocondensation of thioamides and alkynyl(aryl)iodonium reagents affords 1,3-thiazoles in the presence of solid K2C03.37 Reaction of... 

Comparisons of product distributions in thermal and photochemical solvolyses show that the primary vinyl cation is not involved in thermolysis but is formed photochemically. The chirality probe approach using optically active 4-methylcyclohexylidenmethyl(aryl)iodonium tetrafluoroborate 19 was applied to the photosolvolysis.24 The rearranged product 4-methylcycloheptanone retained some optical activity, but the enantiomeric product in slight excess has a different structure depending on the iodoarene leaving group Arl of the substrate. The results indicate that the primary vinyl cation involved is not in a free, dissociated achiral form. 

Cycloaddition of benzyne intermediates with aminothiazadienes provide access to substituted 2,4-diamino-4//-l,3-benzothiazines 196 in high yields. The benzynes are prepared by the treatment of (phenyl)[o-(trimethylsilyl)aryl]-iodonium triflates with 1.5 equiv of tetrabutylammonium fluoride (Scheme 20). Interestingly, 3-substituted-l,2-benzisothiazoles 197 are obtained when 4 equiv of tetrabutylammonium fluoride is used <2005H(65)1615>. 

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],... 

Long-lived vinyl cations have been reviewed.114 Vinyl cations (67) can be prepared by the fragmentation of alkenyl(aryl)iodonium friflates, giving triflate capture products, some of which may be rearranged.115 Otherwise vinyl cation research has been quiet this year. 

It has been shown that selective a-vinylation of enolate anions derived from 1,3-dicarbonyl compounds can be achieved by reaction with 4-/-butyl-1 -cyclohexenyl-(aryl)iodonium and 1-cyclopentenyl(aryl)iodonium tehafluoroborates without competing a-arylation, provided that the alkenyliodonium salt used bears a / -mcthoxyphcnyl, rather than phenyl, group.24... 

Ochiai et al.369 have developed a method for the synthesis of alkenyl(aryl)iodonium ions with the use of trimethylvinylsilanes and idosobenzene [Eq. (4.107)]. Product formation is stereospecific with retention of configuration. 

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... 

The self-condensation of iodosylbenzene was the first reported synthesis of a diaryliodonium salt back in 1892. The mechanism of the reaction was delineated only recently. This approach served for the synthesis of p-(phenylene)bis-(aryliodonium) salts [47], as well as some oligomers from (diacetoxyiodo)ben-zene and triflic acid [117], followed by coupling with an arene (Scheme 39). Under suitable conditions the same reaction can lead to simple phenyl(aryl)-iodonium triflates [118]. 

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]. 

In a similar manner, lLf,lH-perfluoroalkyl(aryl)iodonium triflates 44 are best prepared by the reaction of triflates 43 with trimethylsilylarenes under mild conditions (Scheme 19) [39]. 

Perfluoroalkyl(phenyl)iodonium sulfonates 42 (also known as FITS reagents), as well as lFf,lff-perfluoroalkyl(aryl)iodonium triflates 44, have found practical application as electrophilic fluoro alkylating reagents toward a... 

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). 

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