Iodonium derivatives

Tetraethylammonium tellurocyanate has been prepared and the electrochemical oxidation of the TeCN anion in acetonitrile studied. The reaction takes place with the transitory formation of the [(TeCN)3] complex ion, which then gives the unstable (TeCN)2 dimer this in turn decomposes into tellurium and cyanogen. Extending the earlier preparation and spectral study of several tetra-halogenoaryltellurates(iv) ArTeX, the ammonium, sulphonium, selenonium, arsonium, and iodonium derivatives have been prepared, thus giving more complete spectral data. ... 

Two structural types of cyanoiodonium salts are known (dicyano)iodonium triflate, (NC)2lOTf [399,400] and aryl(cyano)iodonium derivatives, Arl(CN)X [ 146,460,508,509]. (Dicyano)iodonium uiflate 277 can be prepared by the reaction of iodosyl triflate (375) (Section 2.1.1.2) with cyanotrimethylsilane in dichloromethane (Scheme 2.105). In the solid state, compound 277 is thermally unstable and air-sensitive it completely decomposes at room temperature in 2-5 min forming cyanogen iodine, ICN and explodes when exposed to air. However, it can be stored at -20 °C under nitrogen for several days [400]. Despite its low stability, cyanide 277 can be used in situ for the very mild and efficient preparation of various bis(heteroaryl)iodonium salts by an iodonium transfer reaction with the respective stannylated heteroarenes (Section 2.1.9.1.1). 

Fluoroalkyl(aryl)iodonium salts are the most stable and practically important class of alkyl(aryl)iodonium derivatives. The application of such salts as electrophilic fiuoroalkylating reagents was reviewed in 1996 by Umemoto [1017]. Perfluoroalkyl(phenyl)iodonium trifiates (FITS reagents) 764 are efficient perfluoroalky-lating reagents toward various nucleophiUe substrates, sueh as arenes, carbanions, alkynes, alkenes, carbonyl compounds, amines, phosphines and sulfides [1017]. Scheme 3.300 shows several representative examples of electrophilic perfluoroalkylations using FITS reagents. 

A summary of the biological properties of iodonium salts has been provided in a 1996 review [1]. Among the numerous known structural types of polyvalent organic iodine compounds, only aryl- and heteroaryliodonium salts and iodonium ylides have considerable, practically useful biological activity. Table 7.1 provides a brief description of the specific biological activity of several patented iodonium derivatives. 

Here we describe the reactions of C-H activation of arenes and C-X activation of halogen alkanes with a quasi-borinium cation generated from the iodonium derivative of cobalt bis(dicarbollide) [/u.-8,8 -I-3,3 -Co(1,2-C2B9Hjq)2], as well as an assessment of the Lewis acidity of this highly reactive intermediate. 

Ermolenko MS, Budylin VA, Kost AN (1978) Nucleophihc substitution in iodonium derivatives of indole. Chem Heterocycl Comp (Engl Transl) 14 752-754... 

Polyatomic Cations. Polyatomic cations derived by addition of more protons than required to give a neutral unit to polyatomic anions are named by adding the ending -onium to the root of the name of the anion element for example, PH4, phosphonium ion HjU, iodonium ion H3O+, oxonium ion CH3OHJ, methyl oxonium ion. 

The regiochemistry of the hydrozirconation of disubstituted stannyl- [24, 167-170] and silyl- [171] acetylenes and boron- [118, 172-175] and zinc- [34, 126] alkynyl derivatives result in the formation of 1,1-dimetallo compounds. Hydrozirconation of alkynyliodonium salts affords alkenylchlorozirconocenes with the Zr-C bond geminal to the iodonium moiety [176]. These zirconocene complexes allowed the preparation of ( )-trisubstituted olefins (Scheme 8-20). 

Iodination of moderately reactive aromatics can be effected by mixtures of iodine and silver or mercuric salts.31 Hypoiodites are presumably the active iodinating species. Bis-(pyridi nc)iodonium salts can iodinate benzene and activated derivatives in the presence of strong acids such as HBF4 or CF3S03H.32... 

Rh2(OAc)4-catalyzed decomposition of 2-diazocyclohexane-l,3-dione 380a or its 5,5-dimethyl derivate 380b in the presence of an aryl iodide leads to an iodonium ylide 381 355). The mild reaction conditions unique to the rhodium catalyst are essential to the successful isolation of the ylide which rearranges to 382 under the more forcing conditions required upon copper catalysis (copper bronze, Cu(acac)2, CuCl2) 355). 

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],... 

A versatile and regioselective synthesis of benzo[b]furans, naphthalenes, indoles and benzothiophenes was achieved by reaction of o-alkynylarene and heteroarene carboxaldehyde derivatives in the presence of iodonium ions. The reaction mechanism was also discussed <06CEJ5790>. 

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>. 

The synthesis and chemistry of iodonium thiophene derivatives have been studied <00AM133, 00TL5393>, for example, the preparation of 46 involved the ipso substitution of 2-stannylthiophene 45 <00CC649>. A similar ipso substitution of 2-stannylbenzo[b]thiophene 47 with tetranitromethane gave 2-nitrobenzo[ >]thiophene (48) . 

In this approach, the glycosyl donor and the glycosyl acceptor are linked by the 2-OH of the donor and the free OH of the acceptor. It is one of the most predictable and reliable methods for achieving 1,2-cis stereocontrol. Acetals, mixed p-methoxybenzylacetals and silicon tethering have been widely used as well as iodonium mediated tethering acetals derived from vinyl, allyl and allenyl ethers. These methodologies have been revised.6,76... 

Methylene sugars are versatile starting compounds for the synthesis of aromatic and hydroxymethyl C-glycosyl compounds (71) and of double-ended C-glycosyl compounds (70). The double bond undergoes 1,3-dipolar cycloadditions to give isoxazoline derivatives (71), such as that used as a model for the synthesis of tunicamycin. Also, reaction with iodonium sym-... 

The reactions involved are unimolecular, and the cyclohexenyl derivative 3 undergoes solely the spontaneous heterolysis while both spontaneous heterolysis and ligand coupling occur with the iodane 14. The relative contributions of the two reactions of 14 depend on the solvent polarity. The results summarized in Table I show that the iodonium ion and the counteranion are in equilibrium with the hypervalent adduct, X3-iodane. The equilibrium constants depend on the identity of the anion and the solvent employed, and the iodane is less reactive than the free iodonium ion as the k /k2 raios demonstrate. Spontaneous heterolysis of 3 occurs more than 100 times as fast as th t of the adduct 14 as observed in methanol the leaving ability of the iodonid group is lowered by association by more than 100 times. 

An elecrophilic Br+ or I+ can be successfully transferred to hydroquinidine (13) and two of its commercially available derivatives (4-chlorobenzoate and 9-phenanthryl ether hydroquinidines) simply by mixing two equivalents of the hydroquinidine with one equivalent of sym(co d ne)2-X+ perchlorate in methylene chloride or acetonitrile. H NMR studies (31) showed that the iodonium ion was associated with the nitrogen at the quinuclidine portion of the hydroquinidine instead of the aromatic nitrogen and also that all of the sym-collidines were removed from the X+ since only free collidine and no collidine-I+ peaks were observed. The (hydroquinidine)2-halonium ion is stable in solution for more than 30 minutes at room temperature these ions (and their parent amines) are more soluble in methylene chloride than in acetonitrile, and having R group other than hydrogen also improves the solubility. 

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