Bis iodonium salt

A similar procedure was used for the preparation of several bicyclic enediynes 78 from bis-iodonium salts 62 and alkynylstannanes (Scheme 36) [61]. This coupling reaction was recently utilized in the synthesis of novel dinu-clear complexes with a photochromic bridge [62]. 

Other alkynyl phenyliodonium arylsulphonates were prepared by modified procedures, notably from iodosylbenzene and alkynylsilanes, in good yields (62-89%). The decomposition stage proceeded also in satisfactory yields, up to 88% [61]. Bis alkynyl dibenzoates and ditosylates were prepared from the corresponding bis iodonium salts of the general formula PhI+C=C(CH2) C=CI + Ph, where n = 5,6,8 [62]. 

Diphenyloxyacetylene was prepared from lithium phenyloxide and a bis iodonium salt of acetylene. 

With bis-iodonium salts 56, bis-insertion products 57-59 are observed [52], as summarized in Scheme 3-6. 

The preparation and chemistry of cyclic iodonium salts has been summarized in a review of Grushin [361]. Several examples of known cyclic iodonium salts are shown in Figure 2.10 and include 4,5-phenanthryleneiodonium salts (239) [362], 10//-dibenz[fe,e]iodinonium salt (240) [363], 10,11-dihydrodibenz[fe,/]iodeponium salt (241) [363], phenoxiodonium salt (242) [363], 10-acetylphenaziodonium salt (243) [363], 10-oxidophenothiiodonium salt (244) [363], the bicyclic bis-iodonium salt 245 [364], ben-ziodolium chloride 246 [359] and iodolium salt 247 [365],... 

Various iodonium salts are potent sequestering agents for PQQ [161]. In particular, bis-iodonium salts 54 and 55 inhibit PQQ at a nanomolar level (7-13 nM) and are nearly a 1000 times better inhibitors of PQQ than PhalCl and DPI (52). The potential implication of this activity is in the possible uses of bis-iodonium salts as biocides and in particular as a new class of antimicrobial agents [161]. 

Triarylbismuthines have been synthesized by means of the Nesmeyanov reaction that employs an arenediazonium salt such as the tetrafluoroborate, a bismuth trihahde, and a reduciag agent (51). The decomposition of iodonium salts ia the preseace of bismuth trichloride and metallic bismuth also leads to the formation of triarylbismuthines, Ar Bi (52) ... 

The benzoiodoxol 2035 is converted by Me3SiN3 19 into 2036, which oxidizes cyclohexene to a-azidocyclohexanone 2037 [192], whereas 2035 reacts with bis(trimethyl-silyl)acetylene 2038 to give the iodonium salt 2039 [193] (Scheme 12.57). 

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... 

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. ... 

Electron transfer to the xanthenes, particularly reduction with amines, has been used for a number of years to initiate acrylate polymerization. A typical system is that reported to form volume holograms—lithium or zinc acrylate, triethanolamine and Eosin, Erythrosin, or Rose Bengal [290], Similar mixtures are used to form printing plates photoreducible dye, phenylac-ridine, and acrylate monomer [292], A recent patent application discloses aryl iodonium salts, Rose Bengal, and oxidizable triazines such as 2-methyl-4,6-bis(trichloromethyl)-s-triazine to polymerize acrylates [292],... 

Sonochemically induced cation radical intramolecular cyclization upon the action of an iodonium salt was also demonstrated (Arizawa and others 2001). Being oxidized with phenyliodonium bis(trifluoroacetate), l-(3-anisyl)-2-(l,3-cyclohexadien-2-yl) ethane forms the cation-radical and then 5 -methoxyspiro[cycloxehane-l,l -indan]-2,6-dione. The yield of this final product is high enough. 

Iodo dimethyl amido complexes, with Ti(IV), 4, 331-332 Iodonium salts, cross-coupling with lead reagents, 9, 413 Ionic addition reactions, mechanisms, 1, 101 Ionic bis(isonitrile) complexes, liquid crystals, 12, 280 Ionic character, organometallic compound dn configuration,... 

Keywords. [Bis(acyloxy)iodo]arenes, Dialkoxyiodanes, (Dichloroiodo)arenes, (Difluoroio-do)arenes, Iminoiodanes, Iodanes, Iodonium salts, Iodosyl compounds, Iodyl compounds, Ylides... 

A special method was needed for the synthesis of bis(pentafluorophenyl)-iodonium salts this was achieved either by reaction of pentafluoroiodobenzene with C6F5Xe+ TfO- or, more conveniently, from pentafluorobenzene and I(OOC-CF3)3 in strongly acidic conditions [101]. 

Tetraphenylstannane was the reagent of choice for the conversion of two chiral precursors, i.e. 2-(diacetoxyiodo)- and 2,2 -bis(diacetoxyiodo)-l,r-binaph-thyls, into chiral iodonium salts (Scheme 35) [106]. 

Special iodonium salts. A range of o-trimethylsilyl-phenyliodonioarenes [111] and heteroarenes [112] as well as some similar Wc-compounds coming from norbornadiene [113] and o-carborane [114] have been obtained from the corresponding bis trimethylsilyl precursors upon reaction with one equivalent of (diacetoxyiodo)benzene. These compounds are useful for their facile in situ conversion into benzyne-type intermediates for benzyne itself the whole procedure is available in Organic Syntheses [115]. A recent improvement involved the synthesis of a new benzyne precursor illustrated in Scheme 38 [116]. 

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]. 

A new type of iodonium salts constitute the conformationally rigid, tetranu-clear macrocyclic ring systems dubbed molecular boxes. The relatively simpler tetraaryltetraiodonium salts were obtained from 4,4 -bis(diacetoxyiodo)bi-phenyl and 4,4 -bis(trimethylsilyl)biphenyl [119]. The iodonium salt derived from 4-(4 -lithiophenyl)pyridine was made using the method of /J-(dichloroio-do)chloroethylene and it was used for the construction of hybrid iodonium-platinum (or palladium) cationic tetranuclear macrocyclic squares including some in which the ligand of the metal was a chiral biphosphine [120,121]. 

The use of hypervalent iodine reagents in carbon-carbon bond forming reactions is summarized with particular emphasis on applications in organic synthesis. The most important recent methods involve the radical decarboxylative alkylation of organic substrates with [bis(acyloxy)iodo]arenes, spirocyclization of para- and ortho-substituted phenols, the intramolecular oxidative coupling of phenol ethers, and the reactions of iodonium salts and ylides. A significant recent research activity is centered in the area of the transition metal-mediated coupling reactions of the alkenyl-, aryl-, and alkynyliodonium salts. 

The purpose of present review is to summarize the application of different classes of iodine(III) compounds in carbon-carbon bond forming reactions. The first two sections of the review (Sects. 2 and 3) discuss the oxidative transformations induced by [bis(acyloxy)iodo] arenes, while Sects. 4 through 9 summarize the reactions of iodonium salts and ylides. A number of previous reviews and books on the chemistry of polyvalent iodine discuss the C-C bond forming reactions [1 -10]. Most notable is the 1990 review by Moriarty and Vaid devoted to carbon-carbon bond formation via hypervalent iodine oxidation [1]. In particular, this review covers earlier literature on cationic carbocyclizations, allyla-tion of aromatic compounds, coupling of /1-dicarbonyl compounds, and some other reactions of hypervalent iodine reagents. In the present review the emphasis is placed on the post 1990s literature. 

Apart from the above two major general reaction pathways, there are some further possibilities for instance, [bis(trifluoroacetoxy)iodo]benzene reacts as an ambident electrophile and is attacked by hard nucleophiles at its carbonyl carbon, whereas iodylarenes may react similarly from carbon rather than iodine. Alkynyl iodonium salts are actually tetraphilic electrophiles, whereas iodosylbenzene reacts also as a nucleophile from oxygen. Diaryl iodonium salts serve as arylating reagents, mostly homolytically other iodonium salts transfer groups such as perfluoroalkyl, vinyl, alkynyl or cyano to several nucleophiles in various ways. 

Trimethylsilyl cyanide (0.54 ml, 4 mmol) was added to a stirred suspension of iodosyl triflate (0.58 g, 2 mmol) in dichloromethane (15 ml) at — 78°C under nitrogen. The mixture was allowed to warm to — 20°C and stirred at this temperature for 15 min until the formation of a clear solution. The solution was cooled to — 78°C and transferred to a cold stirred solution of the appropriate tributyltin heterocycle (4 mmol) in dichloromethane (15 ml). The mixture was brought to room temperature and crystallized by the addition of dry hexane (20-30 ml). The precipitated iodonium salt was filtered under nitrogen, washed with dry ether (30 ml) and dried in vacuo. Mono or bis hetaryl iodonium salts prepared by these and related methods also involved groups coming from selenophene [23], pyrazoles [24], benzothiophene [21], etc. 

Ethylene reacted with iodonium salts in the presence of a palladium catalyst and a base to afford directly 1,2-bis arylated products (stilbenes). Styrene underwent arylation under similar conditions [44], Allylic cyclic carbonates were efficiently phenylated by diphenyliodonium tetrafluoroborate because of the mild conditions, no ring opening occurred, as was the case when iodobenzene was used. 

Whereas oxygen nucleophiles gave poor yields of alkenylated products with alkenyl iodonium salts, the reactions with sulphur nucleophiles proceeded more efficiently, leading to unsaturated sulphides and sulphones. Thus, 4-t-butylcyclohexenyl phenyliodonium salts afforded with sodium thiophenoxide 4-t-butylcyclohexenyl phenyl sulphide (81%) [3] and with sodium phenylsulphinate the corresponding sulphone (29%) in the presence of 18-crown-6, the yield of the latter rose to 80% [45]. jS-Phenylsulphonylalkenyl iodonium salts with sodium phenylsulphinate at 0°C, without any catalyst, afforded Z-l,2-bis(phenylsulphonyl)alkenes, in high yield with retention of the stereochemistry [45] ... 

An alternative approach for alkynyl carboxylates involved reaction between [bis(acyloxy)iodo]benzenes and lithium acetylides [59]. Alkynyl iodonium salts afforded with sodium carboxylates in the presence of water 1-acyloxyketones heating in an excess of acetic acid gave similarly a-acetoxy ketones [60], Alkynyl tosylates and mesylates were obtained from the thermal decomposition of isolable alkynyl iodonium sulphonates. 

Sodium thiophenoxide and bis phenyliodonium acetylene triflate afforded cleanly l,2-bis(phenylthio)acetylene [6]. Alkynyl iodonium salts have alkynylated several arene sulphonates which were converted into alkynyl aryl sulphones. The process is probably the best among other methods, as far as yield, availability of starting materials, non-toxicity and ease of handling are concerned. 

In some ylides photolytic conditions were necessary for their transylidation [30]. The conversion of iodonium ylides into a-halogeno derivatives of the parent carbonyl compound (or other precursor) with hydrogen halides is normally effected directly, without isolation of their iodonium salts. A similar reaction with halogens leads to the formation of a,a-bis halogenated products [31]. The reaction of pyridines with the non-isolable PhI=C(CN)2 is of interest, since it permits the ready transfer of the C(CN)2 functionality to the nitrogen of pyridine, quinoline, etc. the yields here were generally moderate but in some cases the products could not be obtained using other dicyanocarbene precursors [32],... 

The photochemistry of diphenyl- and bis(4-methylphenyl)iodonium salts has been investigated481,482. Diphenyliodonium halides (140, X = Cl, Br, I) exist as tight ion pairs in acetonitrile. Their photolysis gives almost exclusively iodobenzene by a homolytic cleavage from a charge-transfer excited state. In aqueous acetonitrile, however, the ion pairs are solvent-separated and substantial amounts of 2-, 3- and 4-iodobiphenyls (141) are formed in addition to iodobenzene (142), benzene (143), acetanilide (144) and biphenyl (145) (equation 126). In this medium the photodecomposition occurs via initial heterolysis of the molecule in its excited state, leading to iodobenzene and phenyl cation. 

The halogenonium series. r2Hal(X) and ArAr Hal(X) were synthesized and studied. They resembled iodonium salts very closely for example, the respective iodides, when treated with Mg or Sn (but not Tl, Pb, Bi) powders, produced the organometallics in a yield up to 60% 39), in analogy with the reaction reported by Sandin, McClure, and Irwin 29) for diphenyliodonium salts. 

DeVoe et al. have reported quantitative aspects of photosensitization of diphenyliodonium salt and bis(4-dimethylaminobenzylidene)acetone (DMBA) [101]. This ketone is a bis-vinylog of Michler s Ketone, which is a well-known sensitizer for onium salt initiated free radical polymerizations [102,103], The reaction with DMBA is an example of electron transfer sensitization gated by conformational relaxation of the sensitizer. The ratio of iodonium salt consumption to aminoketone consumption is two, the second iodonium salt equivalent is consumed by a second reducing equivalent from the aminoalkyl radical on the oxidized photosensitizer. 

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