Iodonium

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

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]. 

Efficient homocoupling of the aryi iodonium salt 827 using Zn is catalyzed by Pd(acac)2[708], Homocoupling of the aryisuifonyl chloride 828 as a pseudohalide takes place in the presence of 2 equiv. of Ti tctraisopropoxide[7Q9]. 

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. 

Iodine is only slightly soluble in water and no hydrates form upon dissolution. The solubiHty increases with temperature, as shown in Table 2 (36). Iodine is soluble in aqueous iodide solutions owing to the formation of polyiodide ions. For example, an equiHbrium solution of soHd iodine and KI H2O at 25°C is highly concentrated and contains 67.8% iodine, 25.6% potassium iodide, and 6.6% water. However, if large cations such as cesium, substituted ammonium, and iodonium are present, the increased solubiHty may be limited, owing to precipitation of sparingly soluble polyiodides. Iodine is also more... 

In a procedure known as the iodonium condensation, substituted diaryhodonium compounds react with tyrosines. Thyronines with substituents other than NO2 or I at the 3 and 5 positions are obtained. 

In this case the ylide was not isolated but allowed to react with ben2ophenone to give, after hydrolysis with hydrochloric acid, 1,1-diphenylethylene, diphenylacetaldehyde, and triphenylarsine (160). An excellent method for preparing arsonium ylides involves the reaction between a stable dia2o compound and triphenylarsine in the presence of a copper catalyst such as bis(acetylacetonato)copper(II) (161). Rather than a dia2o compound, an iodonium yhde can be used again a copper catalyst is necessary for an optimum yield of product. An example of the use of a dia2o compound is shown in the formulation of triphenyl arsonium 2,3,4-triphenylcyclopentadienyLide [29629-32-17, C H As ... 

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) ... 

Experiments with unsymmetrical iodonium salts iadicate that the bismuth atom is preferentially arylated by the more electron-attracting aryl group. 

Photopolymerization reactions are widely used for printing and photoresist appHcations (55). Spectral sensitization of cationic polymerization has utilized electron transfer from heteroaromatics, ketones, or dyes to initiators like iodonium or sulfonium salts (60). However, sensitized free-radical polymerization has been the main technology of choice (55). Spectral sensitizers over the wavelength region 300—700 nm are effective. AcryUc monomer polymerization, for example, is sensitized by xanthene, thiazine, acridine, cyanine, and merocyanine dyes. The required free-radical formation via these dyes may be achieved by hydrogen atom-transfer, electron-transfer, or exciplex formation with other initiator components of the photopolymer system. 

Cryptand, iodonium complex equilibrium constant, 7, 746 (80JA6574)... 

H A S S N E R Azide azlridlne synthesis Stereospecific and regioseiective addition of INa (via iodonium ions) or of BrNa (ionic or free... 

While electron beams can produce cations, they are not effective at producing cationic cure in the absence of suitable photoinitiators. The same cationic photoinitiators used for UV cure are often also e-beam sensitive. Examples are triaryl sulfonium or diaryl iodonium salts [41]. 

The anomalous iodoacetamide-fluoride reaction violates this rule, in that a less stable -halonium complex (18) must be involved, which then opens to (19) in the Markownikoff sense. This has been rationalized in the following way estimates of nonbonded destabilizing interactions in the possible products suggest that the actual product (16) is more stable than the alternative 6)5-fluoro-5a-iodo compound, so the reaction may be subject to a measure of thermodynamic control in the final attack of fluoride ion on the iodonium intermediate. To permit this, the a- and -iodonium complexes would have to exist in equilibrium with the original olefin, product formation being determined by a relatively high rate of attack upon the minor proportion of the less stable )9-iodonium ion. 

Iodine isocyanate was used to synthesize the first steroidal aziridine, 2, 3 -iminocholestane (95). from 5a-cholest-2-ene (91). This reaction sequence which is believed to proceed through a three-membered ring iodonium ion (92) illustrates the limitation of pseudohalogen additions for the synthesis of -aziridines. The iodonium complex forms from the least hindered side (usually alpha) and is opened tmK5-diaxially to give a -oriented nitrogen function. The 3a-iodo-2 -isocyanate (93) is converted by treatment with... 

Oxo-bridged diiodonium triflate [Zefirov s reagent), a useful reagent for the synthesis of triflate esters and iodonium salts, can be prepared by the treatment of lodosobenzene with triflic anhydride [92] or by the reaction of lodobenzene diacetate with tnflic acid [93] (equation 44). 

Another useful reagent for the preparation of alkynyl lodonium Inflates is [cyano(trifluoromethylsulfonyloxy)(phenyl)]iodine [/i7, 138, 139, 140] prepared from iodosobenzene, trimethylsilyl tnflate, and trimethylsilyl cyanide (equation 71). This reagent reacts with various stannylacetylenes under very mild conditions to form the corresponding alkynyl iodonium salts in high yields [139] (equation 72)... 

In contrast to the previous method (equation 70), reaction 72 made possible the preparation of iodonium triflates from functionalized acetylenes bearing an electron-withdrawing group such as tosyl, cyano, or carbonyl [138]. Of special interest is the application of this method to the synthesis of the bisiodonium acetylenic salt [139, 140] (equation 73). 

Alkynyl iodonium triflates prepared by the above reactions (equations 70,72, and 73) have become valuable reagents m organic chemistry, serving as premier... 

Low yields of C-arylated ketones have also been obtained by reaction of pyrrolidine enamines with diaryl iodonium salts (68). 

Most N-phenyl quaternary salts are not prepared by direct quater-nization but rather by introducing the nitrogen substituent before ring closure. It has recently been found that diphenyl iodonium boro-fluoride reacts smoothly with pyridine the phenyl carbonium ions formed give the 1-phenylpyridinium ion good yield. ... 

The initiating radicals are assumed to be SCN, ONO or N3 free radicals. Tris oxalate-ferrate-amine anion salt complexes have been studied as photoinitiators (A = 436 nm) of acrylamide polymer [48]. In this initiating system it is proposed that the CO2 radical anion found in the primary photolytic process reacts with iodonium salt (usually diphenyl iodonium chloride salt) by an electron transfer mechanism to give photoactive initiating phenyl radicals by the following reaction machanism ... 

Triphenylsulfonium tetrafluoroborate [(C6Hs)3 S" BF4 ] is used instead of diphenyl iodonium chloride to give phenyl radical as the initiating species. Potassium [tris(oxalato) cobaltate) (III)] with diphenyl iodonium chloride also has been used as the photoinitiator of acryl-... 

Unsaturated carboxylic acid 17 possesses the requisite structural features for an iodolactonization reaction.16 A source of electrophilic iodine could conceivably engage either diastereoface of the A20,21 double bond in 17. The diastereomeric iodonium ion inter-... 

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