Phenyl iodonium triflate

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],... 

Diarylmethylenecyclopropa[6]naphthalenes 14, unlike their benzene parent counterparts which give cycloaddition reactions at the cyclopropene bridge bond [10a], react on the exo double bond in Diels-Alder cycloadditions (see Sect. 2.1.1) [10b]. The reactions of 14 with the highly electron-deficient acetylenic(phenyl)iodonium triflate 584 give products 586a and 587, which are believed to derive from unstable primary [2 + 2] cycloadducts 585 (Scheme 82) [10b],... 

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],... 

The use of alkynyliodonium salts in the synthesis of 2,3-disubstituted 4,5-dihydrofurans was reported by Feldman. In this conversion, the addition of p-toluenesulfinate to ethers of 1-hydroxybut-3-ynyl(phenyl)iodonium triflates 79 induces a series of reactions that afford eventually 2-substituted 3-p-toIuenesulfonyl-4,5-dihydrofurans 80 . 

A study of the regioselectivity of the 1,3-dipolar cycloaddition of aliphatic nitrile oxides with cinnamic acid esters has been published. AMI MO studies on the gas-phase 1,3-dipolar cycloaddition of 1,2,4-triazepine and formonitrile oxide show that the mechanism leading to the most stable adduct is concerted. An ab initio study of the regiochemistry of 1,3-dipolar cycloadditions of diazomethane and formonitrile oxide with ethene, propene, and methyl vinyl ether has been presented. The 1,3-dipolar cycloaddition of mesitonitrile oxide with 4,7-phenanthroline yields both mono-and bis-adducts. Alkynyl(phenyl)iodonium triflates undergo 2 - - 3-cycloaddition with ethyl diazoacetate, Ai-f-butyl-a-phenyl nitrone and f-butyl nitrile oxide to produce substituted pyrroles, dihydroisoxazoles, and isoxazoles respectively." 2/3-Vinyl-franwoctahydro-l,3-benzoxazine (43) undergoes 1,3-dipolar cycloaddition with nitrile oxides with high diastereoselectivity (90% de) (Scheme IS)." " ... 

The reaction of lithium or sodium arylteUurolate with alkynyl phenyl iodonium triflates or tosylates. ... 

Cyano)(trifluoromethanesulfonoxy)-iodojbenzene or cyano(phenyl)-iodonium triflate... 

Stang etal. (94JA93) have developed another alkynyliodonium salt mediated approach for the synthesis of y-lactams including bicyclic systems containing the pyrrole moiety. This method is based on the formation of 2-cyclopentenones 114 via intramolecular 1,5-carbon-hydrogen insertion reactions of [/3-(p-toluenesulfonyl)alkylidene]carbenes 113 derived from Michael addition of sodium p-toluenesulfinate to /3-ketoethynyl(phenyl) iodonium triflates 112 (Scheme 32). Replacing 112 by j8-amidoethynyl (phenyl)iodonium triflates 115-119 provides various y-lactams as outlined in Eqs. (26)-(30). 

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. 

Reaction of some / -trifyloxy-vinyl(phenyl)iodonium triflates with aryllithi-ums can lead to the synthesis of diaryliodonium salts in a manner analogous to... 

Other similar approaches have used alkenylsilanes and PhI0/Et30+ BF4 and also alkenylstannanes and PhI+CN TfO [123,124]. The reactions proceed also stereoselectively. The parent ethenyl(phenyl)iodonium triflate as well as several trisubstituted alkenyl members were obtained in this way. In an analogous manner E-alkenylzirconium compounds upon reaction with (diacetoxyiodo)ben-zene afforded -alkenyl(phenyl)iodonium salts stereoselectively [125]. 

The palladium/copper-cocatalyzed coupling of the readily available trisubsti-tuted alkenyl(phenyl)iodonium triflates 77 with alkynyl- and alkenylstannanes proceeds under exceedingly mild conditions with retention of geometry of the alkenyl ligand of the iodonium salt (Scheme 35) [60]. 

A variety of five-membered nitrogen heterocycles can be prepared efficiently by inter- or intramolecular addition/cyclizations of sulfonamide anions with alkynyliodonium salts. The intermolecular variant employs the combination of the amides 172 or anilides 174 with propynyl(phenyl)iodonium triflate (Scheme 65) [131,132]. The yield of dihydropyrroles 173 in this cyclization is extremely sensitive to the nature of the protective group P the tosyl group in 172 proved... 

A similar intermolecular cyclization was recently utilized in the synthesis of highly substituted dihydropyrrole derivatives [133 -135]. In a specific example, the addition of pentadienyltosylamide derivatives 177 to propynyl(phenyl)iodo-nium triflate initiates a sequence of transformations that furnishes the complex, highly functionalized cyclopentene-annelated dihydropyrrole products 178 in moderate yields with complete stereoselection (Scheme 66). Under similar reaction conditions, the isomeric isoprene-derived tosylamide 179 reacts with propynyl(phenyl)iodonium triflate to give azabicyclo[3.1.0]hexane 180 as the final product [134]. 

This approach to N-alkynylsulfonamides has been applied to the synthesis of enantiomerically pure derivatives 27 of N-(ethynyl)allylglycine (Scheme 52) [152]. In this case, deprotonated sulfonamide derivatives of (S)-allylglycine were treated with ethynyl(phenyl)iodonium triflate (28), since the trimethylsi-lylethynyl salt 26 was not very effective for this purpose. 

Reactions of silyl, pyranyl, furanyl, and 1,3-dioxanyl ethers, 37, of 4-hydroxy-l-butynyl(phenyl)iodonium triflate with sodium p-toluenesulfinate in THF afford... 

An interesting reaction between the bis phenyl iodonium triflate of acetylene and the silyl enol ether of acetophenone afforded an allene (PhCOCH=C=C=CHCOPh, 84%) [6], Also, alkynyl iodonium tosylates and carbon monoxide in methanol or ethanol, with palladium catalysis, furnished alkyne carboxylates [53]. 

The reactions of / -ketoethynyl- and ) -amidoethynyl(phenyl)iodonium triflates, 17 and 18, with sodium / -toluenesulfinate illustrate the synthetic potential of alkynyliodonium salts33. Although the direct attachment of a carbonyl group to the / -carbon atom of the triple bond in alkynyliodonium ions might be expected to facilitate alkynyl sulfone formation via the Ad-E mechanism, this mode of reactivity has not been observed. Instead, the MC pathway with carbenic insertion dominates and affords sulfones containing the... 

Photochemical activation is not universally required for the conversion of alkynyliodo-nium salts into alkynylphosphonium compounds. For example, triphenylphosphine reacts with various alkynyl(phenyl)iodonium triflates in dichloromethane to give high yields of alkynylphosphonium triflates (equation 71)90. Since these reactions occur readily in the dark and are not inhibited by molecular oxygen or 2,6-di-terr-butyl-4-methylphenol, they are thought to proceed via the MC mechanism (equation 45)90. 

When 5,5-dimethyl-1,3-hexadiynyl(phenyl)iodonium triflate is mixed with two equivalents of triphenylphosphine in toluene, a mixture of bisphosphonium triflates is produced (equation 76)34. This transformation apparently involves the initial formation of (5,5-dimethyl-l,3-hexadiynyl)triphenylphosphonium triflate followed by competing Michael and conjugate Michael reactions of this compound with a second mole of triphenylphosphine. The ( -geometry about the carbon-carbon double bonds in both products has been established by NMR analysis34. 

Certainly one of the most unusual nucleophiles to be treated with alkynyliodonium salts is the tetra-ter -butyltetraphosphacubane shown in equation 7791. However, despite its unique structure, this compound reacts with ethynyl(phenyl)- and l-propynyl(phenyl)-iodonium triflates in the now expected way to give good yields of alkynylphosphonium salts91. 

Vaska s complex, the square planar iridium(I) compound shown in equation 145, readily interacts with alkynyl(phenyl)iodonium triflates in toluene at room temperature21. Such reactions proceed with loss of iodobenzene and deliver octahedral Ir(III) complexes possessing (7-alkynyl and trifluoromethanesulfonato ligands in a Jnms-relationship. The rhodium(I) analog of Vaska s complex behaves in a similar way21. 

Since it is known that halo(phenyl)acetylenes add oxidatively to Vaska s complex to give (7-phenylethynyl iridium(III) halides, 32112, the intervention of phenyliodonium iridium(III) and rhodium(III) intermediates, 33, in the alkynyliodonium reactions seems plausible. In any case, the production of cr-alkynyl complexes with alkynyl(phenyl)-iodonium triflates appears to be both more general and efficient21. 

Alkynyliodonium triflates exhibit two distinct modes of reactivity with bis(triph-enylphosphine)ethyleneplatinum(O)113. When (terf-butylethynyl)phenyliodonium triflate is mixed with the Pt(0) complex in degassed dichloromethane, ethylene insertion occurs, and a cationic 3-propargylplatinum(II) triflate is obtained (equation 147). Employment of l-propynyl(phenyl)iodonium triflate in degassed toluene, on the other hand, leads to a square planar cr-propynylplatinum(II) complex. 

Diels-Alder reactions of alkynyl(phenyl)iodonium triflates (i.e. containing electron-withdrawing groups in the alkynyl moiety) and [bis(phenyliodonium)] ethyne ditrifiate have been employed for the synthesis of cyclic vinyliodonium salts (equations 143 and 144)17,41. The availability of such compounds offers considerable potential for the elaboration of densely functionalized cyclic molecules. 

Phenyl[2-(trimethylsilyl)phenyl]iodonium triflate (226) has emerged as a superior benzyne precursor i.e., admixture of 226 with tetra-n-butylammonium fluoride (TBAF) enables the generation of benzyne in dichloromethane at room temperature (95JCS(CC)983). When organo azides or -nitrones are available in the reaction medium, high yields of the benzotriazoles 227 or benzisoxazolines 228 are obtained (Scheme 62) (98HC205). 

The butynyl(phenyl)iodonium triflates 243, possessing an ether or acetal linkage at C-4, react with sodium />-toluenesulfinate to give the 3-tosyldihydrofurans 244 (00OL2603, OOJOC8659). These formal carbenic C-O bond insertions are thought to occur through vinyloxonium ylide intermediates (Scheme 67). 

Alkynyl(phenyl)iodonium triflates react with pivaldehyde oxime in the presence of iodosylbenzene to give the isoxazoles 278 (Scheme 79) (97TL8793). Although the purpose of iodosylbenzene was to oxidize the oxime to the corresponding nitrile oxide, thus providing access to isoxazolyliodonium salts, its overall influence on the outcome of these reactions has not been firmly established. 

A Simple and Convenient Method for the Preparation of p-Functionalized Alkynyl(phenyl)iodonium Triflates Phenyl[p-toluenesulfonyl)ethynyl]iodonium Triflate. 

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