Phenyl iodonium

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],... 

The alkenyl(phenyl) iodonium salt 725 undergoes the facile cross-coupling with vinylstannane to form the conjugated diene 726[594]. 

The add-catalyzed cyclodehydration of (Z)- and ( )-6-hydroxy-a,p-unsaturared ketones offers a mild synthesis of substituted furans. In the case of ( )-olefins, photochemical isomerisation was found to accelerate the reaction <96TL6065>. Reaction of alkynyl(phenyl)iodonium tetrafluoroborates with tropolone in the presence of a base yields 2-substituted furotropones (Scheme 16, <96TL5539>). 

Muller et al. have also examined the enantioselectivity and the stereochemical course of copper-catalyzed intramolecular CH insertions of phenyl-iodonium ylides [34]. The decomposition of diazo compounds in the presence of transition metals leads to typical reactions for metal-carbenoid intermediates, such as cyclopropanations, insertions into X - H bonds, and formation of ylides with heteroatoms that have available lone pairs. Since diazo compounds are potentially explosive, toxic, and carcinogenic, the number of industrial applications is limited. Phenyliodonium ylides are potential substitutes for diazo compounds in metal-carbenoid reactions. Their photochemical, thermal, and transition-metal-catalyzed decompositions exhibit some similarities to those of diazo compounds. 

C(l)-Tosylation of 57 with [hydroxy(phenyl)iodonium] tosylate resulted in the J-1-tosylate 62 which could be further transformed by Sn2 reactions. Tosylation was proposed to proceed via the addition product 61 which, after Sn2 displacement by the tosylate anion and inversion at C-l, furnished 62 (Scheme 6) <1999T1755>. 

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],... 

Furoxan and furazans alcohols are relatively uncommon compounds, but they can serve as useful precursors to various new derivatives of 1,2,4-oxadiazole. 3-Hydroxy-4-nitrofurazan 208 reacts with iodosylbenzene to produce a highly reactive intermediate phenyliodonium nitrofurazanylate 209 which can be converted to a series of alkynyl(phenyl)-iodonium nitrofurazanylates and related products (Scheme 48) <2001TL5759>. 

Obtained both from phenyl[2-(trimethylsilyl)phenyl] iodonium trifluoromethane sulphonate and 2-trimethylsilylphenyltrifluoromethanesulfonate in the presence of tetrabutylammonium fluoride (TBAF). They are good benzyne precursors under mild conditions. 

Studies conducted in the presence of 0.5 mol% (4-n-octyloxyphenyl)phenyl-iodonium SbF6". Calculated according to the equation ... 

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 . 

Arylethynyl(phenyl)iodonium salts, RC=CI+Ph 4-MeC6H4S03-, react as 1,3-dipolarophiles with nitrile oxides R CNO to afford phenyl(substituted isox-azolyl)iodonium salts 210, which give iodoisoxazoles on reaction with nucleophiles. The crystal structure of 210 (R = Ph, R1 = mesityl) has been determined (369). 

Scheme 4.36. Hydrozirconation of alkynyl(phenyl)iodonium salts.

Two approaches have been applied for the synthesis of imidazo[2,l + thia/,ole ring systems. Reaction of 2-mercapto-benzimidazole with perfluoro-2-methylpent-2-ene in the presence of triethylamine gave compound 419 (Equation 192), and cyclocondensation of 2-imidazolidinethione with the alkynyl(phenyl)iodonium salt 420 afforded product 421 (Equation 193) <2001RCB1446, 2003JCM715>. 

Cyclopentene annelation.1 The reaction of the anion of a 1,3-dicarbonyl compound with l-decynyl(phenyl)iodonium tetrafluoroborate results in an annelated 3-pentylcyclopentene in reasonable yield. The product is considered to result from... 

When 4-/-butylcyclohex-1 -enyl(phenyl)iodonium tetrafluoroborate (3) is heated at 60 °C in chloroform, 1-fluorocyclohexene 4, 1-chlorocyclohexene 5 and l-(o-iodophenyl)cyclohexene 6 are formed with accompanying iodobenzene leaving group (eq 2).3 These three substitution products are best accounted for by formation of an ion pair involving cyclohexenyl cation 7. The cyclohexenyl cation 7 formed picks up fluoride from tetrafluoroborate and chloride from chloroform solvent, and recombines with the iodobenzene generated (eq 3). This kind of reactions with a counteranion and solvent are characteristic of unstable carbocations and are known in the case of phenyl cation generated from the diazonium salt in the Schiemann-type reaction.4... 

Reactions of 3 in alcoholic and aqueous solvents result in a normal solvolysis product 8 (and cyclohexanone 9) as well as the recombination product 6 (eq 4).5 This is again rationalized by an ion-pair mechanism. 2-Methylcyclohex-l-enyl(phenyl)iodonium tetrafluoroborate (10) undergoes solvolysis about 250 times as fast as 3, and gives some rearranged product 12 in accord with the SnI solvolysis mechanism (Scheme 1). 

Interesting results concerning phenyl group participation were observed with ( )-styryl(phenyl)iodonium tetrafluoroborate (26) using a deuterated substrate (eq 12)16 When 26-ad was heated in trifluoroethanol (TFE) at 60 °C, slow reaction gave die E isomer of substitution product 28 quantitatively, but the deuterium was completely scrambled between the a and p positions. This strongly indicates that a symmetrical intermediate is involved during the reaction and the most reasonable one is vinylenebenzenium ion (27) formed by phenyl participation. This intermediate also explain the exclusive formation of the retained ( )-28. 

Photosolvolysis of some vinyl iodonium substrates can be compared with thermal solvolysis of the same substrates. Photochemical reaction of (E)- and (Z)-2-phenylprop-l-enyl(phenyl)iodonium tetrafluoroborate (31) in methanol and TFE gave products of heterolytic cleavage of vinylic C-I bond as summarized in Table III (for the product structures see eq 14.17 In contrast to... 

S-Alkynyl phosphorodithionates have been prepared in high yield by the nucleophilic displacement of iodobenzene from alkynyl phenyl iodonium salts [65]. 

Reactions of (ii)-l-decenyl(phenyl)iodonium salt (6a) with halide ions have been examined under various conditions. The products are those of substitution and elimination, usually (Z)-l-halodec-l-ene (6b) and dec-l-yne (6c), as well as iodobenzene (6d), but F gives exclusively elimination. In kinetic studies of secondary kinetic isotope effects, leaving-group substituent effects, and pressure effects on the rate, the results are compatible with the in-plane vinylic mechanism for substitution with inversion. The reactions of four ( )-jS-alkylvinyl(phenyl)iodonium salts with CP in MeCN and other solvents at 25 °C have been examined. Substitution with inversion is usually in competition with elimination to form the alk-l-yne. 

Evidence for a Michael addition of a nucleophile to alkenyl(phenyl)iodonium salts at the Cp atom has now been reported for the first time. Nucleophilic vinylic substitutions of (Z)-(/3-bromoalkenyl)iodonium tetrafiuoroborates (161) and its (Z)-(/3-chloroalkenyl) analogue with sodium benzenesulfinate in THE afforded stereoselectively (Z)-l,2-bis(benzenesulfonyl)alkene (163) with retention of configuration. Intermediate formation of (Z)-[/3-(benzenesulfonyl)alkenyl]iodonium salt (162) in these reactions was established by NMR experiments in CDCI3. The formation of (Z)-(162) involves a hitherto unobserved Michael addition of benzenesulfinate anion to the alkenyliodonium salts at the Cp atom, followed by halogen extrusion. ... 

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. ... 

Typical procedure. To a stirred solntion of Ph2TeCl2 (716 mg, 1.40 mmol), PdClj (25 mg, 0.14 mmol) and NaOMe (220 mg, 4.20 mmol) in CHjCN/MeOH (20 mL) under nitrogen atmosphere was added p-methoxyphenyl(phenyl)iodonium tetrafluoroborate (556 mg, 1.40 mmol) at room temperatnre. The reaction mixture was stirred at room temperature for 7 h. The reaction mixture was extracted with diethyl ether (3x20 mL). The organic layer was dried over anhydrous sodium sulphate and evaporated in vacuo. The crude product was separated by Si02 column chromatography (hexane, Rf=0.l7) to afford the conpled product (219 mg, 85%). 

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). 

Alkynyl(phenyl)iodonium Tosylates Preparation and Stereospecific Coupling with Vinylcopper Reagents. Formation of Conjugated Enynes P. J. Stang and T. Kitamura, Department of Chemistry University of Utah, Salt Lake City, UT 84112... 

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