Aryl iodonium triflates

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>. 

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

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]. 

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... 

Alkenyl aryl iodonium triflates. By using alkynes to capture [PhlPJ OTL, which is derived from Phi and FXeOTf, mixed iodonium triflates are readily obtained. 

Other coupling partners to organozinc reagents include heterocyles such as 2-methylthiobenzothiazole, alkenyl aryl iodonium triflates (alkenyl group transfer for synthesis of trisubstituted alkenes), and aryl heteroaryl ethers. " Improved nickel-catalyzed cross-coupling conditions between oz-rto-substituted aryl iodides-nonaflates and alkyl-zinc iodides in. solution and in the solid phase have been defined. ... 

A similar iodonium exchange reaction involves aryl(cyano)iodonium triflates 278 and stannylated aromatic precursors providing many kinds of diaryl or aryl(heteroaryl) iodonium salts [145,147,401], Tykwinski, Hinkle and coworkers have reported an application of such iodonium transfer reaction for obtaining of a series of mono- and bithienyl(aryl)iodonium triflates 279 with increasingly electron-withdrawing substituents on the aryl moiety (Scheme 2.81) [401], Thienyl and bithienyl iodonium salts prepared by iodonium transfer reaction using PhI(CN)OTf are potentially useful as nonlinear optical materials [402],... 

A similar approach to aryl- and heteroaryl(phenyl)iodonium triflates 285 involves the ligand-transfer reaction between vinyliodonium salt 284 with aryllithiums (Scheme 2.83) [405]. Likewise, the reaction of ( )-[(3-(trifluoromethanesulfonyloxy)ethenyl](aryl)iodonium triflates 286 with aryllithiums or alkynyllithiums can be used for a selective preparation of the respective diaryl- or alkynyl(aryl)iodonium triflates in high yields [406]. 

A very general and mild procedure for the stereospecific synthesis of aIkenyl(aryl)iodonium triflates 309 involves aryl(cyano)iodonium triflates 308 as iodonium transfer reagents in reactions with stannylated alkenes 307 (Scheme 2.89) [367,443,444], This method was also applied to the preparation of the parent vinyliodonium triflate from tributyl(vinyl)tin [445],... 

Similarly functionalized alkenyl(aryl)iodonium triflates 312 were prepared by the addition of (aryl)fluoroiodonium triflates 311 to terminal alkynes (Scheme 2.91) [45,48]. 

Synthesis of 3,3-disubstituted oxindoles from arylation- and vinylation-carbocycUzation of electron-deficient alkenes with diaryliodonium salts catalyzed by CuCl catalyst was reported by Zhou, Li, and coworkers. A wide range of diaryl and vinyl(aryl)iodonium triflates and various substitutions on phenylacrylamides are compatible for this reaction. Both ( )-physostigmine and ( )-physovenine have been synthesized successfully in 41 and 36% overall yield using this vinyl addition/cyclization method [71]. Fu and coworkers developed a Cul-catalyzed synthesis of oxindole derivatives from readily available Af-alkyl-Af-phenylacrylamides and diaryliodonium triflates [72] (Scheme 8.34). 

The arylation of the i-tributyistannyl glycai 717 offers a synthetic route to chaetiacandin[585,586]. The Pd-catalyzed reactions of the 3-stannylcyclobute-nedione 718 with iodobenzene, and benzoyl chloride[S87], and alkenylation with alkenyl(phenyl)iodonium triflates proceed smoothly by the co-catalysis by Cul[588,589],... 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

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 pareitropone project began quite by accident after an unexpected observation expanded our thinking about potentially accessible targets for alkynyliodonium salt/alkylidenecarbene chemistry (Scheme 18). Treatment of the tosylamide iodonium salt 125 with base under standard conditions was designed to provide no more than routine confirmation of the aryl C-H insertion capabilities, which were first exposed in indoleforming reactions using tosylanilide anion nucleophiles and propynyl(phenyl)iodonium triflate,5b of the intermediate carbene 126. However, this substrate did not perform as expected, since only trace amounts of the 1,5 C-H insertion product 127 was detected. One major product was formed, and analysis of its spectral data provided yet another surprising lesson in alkynyliodonium salt chemistry for us. The data was only consistent with the unusual cycloheptatriene structure 129. 

Phenyl[3-(trimethylsilyl)naphthyl]iodonium triflate (232) has also been described and utilized with aryl azides for synthesis of two naphthotriazoles 233 (98JOC8579). 

Diaryliodonium triflates. The reagent is derived from XeF and TfOH, and it is an oxidant for converting iodoarenes into aryl(iodoaryl)iodonium triflates. 

Aryliodonium salts. Unsymmetrical diaryliodonium triflates and aryl(alkynyl)-iodonium triflates are readily synthesized from the title compounds by reaction with ArLi and alkynyllithium reagents, respectively. Ethylene is one of the byproducts. 

The best and most versatile contemporary method [22] of preparation of alkynyl(aryl)io-donium salts employs readily available alkynylstannanes [23], and the easily prepared [24] cyano(phenyl)iodonium triflate 7 as an iodonium transfer agent in dichloromethane at low temperatures [Eq. (3)]. This procedure provides excellent yields of iodonium triflates 10 and is applicable to a very broad range of alkynylstannanes, including those with strongly electron-withdrawing groups as summarized in Scheme 3-1. Particularly noteworthy and valuable are the P-keto- and P-amido-substituted species 11 and the cyano-functionalized molecule 11 (Y=CN) [25, 26]. 

Various unsymmetrically substituted diaryliodonium triflates 269 can be synthesized by the reaction of iodosylbenzene [380] or (diacetoxyiodo)arenes [381] with arenes in trifluoromethanesulfonic acid (Scheme 2.76). This simple procedure affords diaryliodonium triflates in relatively high yields, but it is limited to aromatic substrates that are not sensitive to strong acids. In a milder, more selective variation of this procedure (diacetoxyiodo)benzene is reacted with arylboronic acids in the presence of triflic acid at -30 °C to afford aryl(phenyl)iodonium triflates in 74-97% yields [377]. 

A very mild and general method for the preparation of diaryl- and heteroaryliodonium triflates is based on iodonium transfer reactions of iodine(III) cyanides with the respective aryl- or heteroarylstannanes [146,148, 399-401]. Specifically, (dicyano)iodonium triflate (277), generated in situ from iodosyl triflate and MesSiCN, reacts with tributyltin derivatives of aromatic and heteroaromatic compounds to afford the corresponding symmetrical iodonium salts under very mild conditions (Scheme 2.80) [389,390]. 

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