Diaryliodonium triflates

Diaryliodonium salts (diaryl-A3-iodanes) are widely used as arylating agents. There are a number of methods available for their synthesis typically involving two or three steps.378,379 A recent one-pot approach, however, offers a simple and high-yielding access to unsymmetrical diaryliodonium triflates using meto-chloroperbenzoic acid (mCPBA) as the oxidant380 [Eq. (4.111)]. Moreover, symmetrical diaryliodonium salts can directly be prepared from iodine and arenes without the use of expensive aryl iodides [Eq. (4.112)]. 

The catalytic influence of 18-crown-6 on the production of fluorobenzene from diphenyliodonium tetrafluoroborate and KF in dichloroethane was documented some years ago [123]. More recently, diaryliodonium salts have been used for direct syntheses of [18F]-fluoroarenes [124,125]. After an initial study in which various counterions were surveyed, this was finally accomplished by the treatment of diaryliodonium triflates and trifluoroacetates with 18F K+-APE 2.2.2 (i.e., the aminopolyether 4,7,13,16,21,24,27-hexaoxa-l,10-diazabicyclo-[8.8.8]hexacosane) or Cs 18F in acetonitrile (Scheme 44). An added feature of these studies is rather extensive confirmation that nucleophiles are preferentially directed to the more deactivated ring of unsymmetrical diaryliodonium ions, unless one of the rings possesses ortho-substituents [125]. 

Similarly, biaryls, including sterically hindered ones, have more recently been obtained by decarboxylative coupling of arenecarboxylic acids and diaryliodonium triflates.93 The PdCla/DPEphos system in the presence of silver carbonate in DMSO was found to be the most efficient, giving yields ranging from 37% to 85% (Scheme 10.61). 

Diaryliodonium triflates are prepared from ArfrOAc) and arenes in triflic acid. Hydrolysis of thioglycosides. Aqueous TfOH and Bu NIO effect hydrolysis of thioglycosides," probably by way of Pummerer reaction. 

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. 

Diaryliodonium triflates. An improved preparative method for aryl phenyli-odonium triflates (10 examples, 74-98% yield) involves reaction of arenes with this reagent in the presence of triflic acid. 

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]. 

Several modified procedures for the preparation of diaryliodonium triflates have been reported in a more recent literature [382-384], Kitamura and Hossain have developed a one-pot reaction to obtain symmetrical diaryliodonium triflates in good yields directly from iodoarenes and aromatic substrates using K2S2O8 as an... 

Olofsson and coworkers have developed several efficient one-pot syntheses of diaryliodonium salts [385-390], A general and universal procedure provides both symmetrical and unsymmetrical diaryliodonium triflates 272 from both electron-deficient and electron-rich arenes 271 and aryl iodides 270 using mCPBA as the oxidant and trifiic acid (Scheme 2.78) [385-387]. The electron-rich diaryliodonium tosylates are prepared similarly using toluenesulfonic acid instead of trifiic acid as the additive [387]. Symmetrical diaryliodonium triflates can be synthesized by a modified one-pot procedure from iodine, arenes, mCPBA and trifiic acid under similar conditions [374,375]. A similar procedure based on a one-pot reaction of arylboronic acids, aryl iodides, mCPBA and BF3 -Et20 has been used for regioselective synthesis of unsymmetrical diaryliodonium tetrafiuoroborates [388,389]. In a further improvement of this approach, a range of... 

A variety of 2-arylbenzo[ ]furans were obtained in good yields by the O-arylation of oximes with diaryliodonium triflates, followed by the treatment with HCl in 1,4-dioxane with warming to initiate a [3,3]-sigmatropic reaction (14H2122). 

Becht, J. M., Le Drian, C., (2008). Biaryl synthesis via decarboxylative Pd-catalyzed reactions of arenecarboxylic acids and diaryliodonium triflates. Organic Letters, 10, 3161-3164. 

Carroll and coworkers developed a metal-free phenylation of anilines with diphenyUodonium trifluoroacetates in DMF at 130 °C [91]. A thorough chemoselectivity study with anilines and diaryliodonium triflates was later performed by the Olofsson group, revealing that electronics are more important than sterics in this transformation, and hence that both the mesityl and the trimethoxyphenyl groups are suitable dummy groups [27]. Carbazoles were efficiently aiylated in toluene at 50 °C in the presence of BuOK [92], and anilines could be obtained in aqueous ammonia at 80 °C (Scheme 5a) [93]. 

Feringa and coworkers reported a copper-catalyzed O-arylation of dialkyl phosphonates and phosphoramidates with diaryliodonium triflates and 2,6-di-ferf-butylpyridine (DTBP), giving easy access to mixed alkyl aryl phosphonates via elimination of one of the alkyl groups as the alkyl triflate prior to arylation (Scheme 10a) [133]. Aryl(mesityl)iodonium salts reacted in a chemoselective way. Copper-catalyzed arylations of hydroxamic acids [134] and carboxylic acids [135] have also been reported, the latter utilizing thiophosphoramides as cooperative catalysts to allow arylation at room temperature. Onomura s group discovered a Cu-catalyzed monoarylation of vicinal diols in toluene at 100 °C. Only traces of product were obtained with alcohols lacking the vicinal hydroxyl group [136]. 

Keywords A-arylsulfonamides, diaryliodonium triflates, copper(I) chloride, potassium phosphate, water, room temperature, lV,N-diarylsulfonamides... 

A copper(I)-catalysed electrophilic ds-carbofunctionalization of alkynes R C=CR with vinyl- and diaryliodonium triflates R ArI+ OTf (R = aryl or CH2=CH) has been reported as a new avenue to vinyl triflates R C(R )=C(OTf)R. The reaction is believed to proceed via the oxidative insertion of Cu(l) into the R -I bond of the reagent, followed by a Cu-coordination to the C=C bond and subsequent yn-addition. The related, CuCl-catalysed reaction of ArX-CH2C=CR (X = CHj, O, NTs) resulted in cyclization towards the aromatic ring. ... 

Other methods exploiting different reactions for in situ formation of the substituted azides in the one-pot click S5mthesis of substituted 1,2,3-triazoles in PEGs were developed. Thus, 1-aryl-subshtuted 1,2,3-triazoles 86 were prepared via the reaction of diaryliodonium triflate 85 with sodium azide, followed by the treatment with terminal alk5mes in aqueous PEG 400 under the copper(I) iodide catalysis (Scheme 50) [79]. The catalyst and the solvent were successfully recovered and reused in three cycles. 

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). 

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