Iodonium compounds

Because visible light is not energetic enough to break chemical bonds, direct production of free radicals by the photoinitiator does not occur. Instead when cationic initiation is needed, as for reaction with epoxies, DIBF is used in conjunction with an iodonium compound such as 4-octyloxyphenyl-phenyliodonium hexaf luoroantimonate (OPPI). It has been proposed that when irradiated, DIBF and OPPI interact to form a cationic species. 

Primary vinyl iodonium compounds (1, R3 = H) are readily prepared as stable salts, but secondary analogs (1, R3 = alkyl) cannot be isolated without the presence of electron-accepting moieties. Cyclopent-l-enyl iodonium salt is very stable and poorly reactive toward bases and nucleophiles, while cyclohept-l-enyl... 

Nurnberger T, Brunner F, Kemmerling BT, Piater L (2004) Innate immunity in plants and animals striking similarities and obvious differences. Immunol Rev 198 249-266 O Donnell VB, Tew DG, Jones OTG, England PJ. (1993) Studies on the inhibitory mechanism of iodonium compounds with special reference to neutrophil NADPH oxidase. Biochem J 290 41 49... 

The valency Of chlorine, bromine, and iodine.—Compounds are known in which the three halogens act as uni-, ter-, quinque-, or septa-valent elements. Usually, however, these elements are univalent. In chlorine dioxide, C102, the chlorine is bi- or quadri-valent.19 In M. Berthelot s hydrogen perchloride, HC13, the chlorine is probably tervalent, and R. Meldola (1888) showed that the oxygen in the hydrochloride of methyl oxide is best regarded as quadrivalent, the chlorine tervalent thus, (CH3)2 0 Cl.H. Iodine also appears to be tervalent in the so-called iodonium compounds. 

J. Stieglitz has pointed out that in A. A. Jakowkin s reaction Cl2+H2O HOCl -f-H +Cr, part of the hypochlorous acid must form positive chlorine and negative chlorine ions in order to produce the neutral molecules Cl2 and H20. The ionization of hypochlorous acid—as an acid—will be HOCW H+OCl and as a base, HOCl =iHO,+Cl . There is also evidence that not only can hypochlorous act as a weak acid, but it can also act as a weak base. The basic properties of hypochlorous acid are illustrated by the iodoso- and iodonium compounds.16... 

From iodine, too, iodonium compounds have been prepared, in which the iodine functions as a triad and a hydroxide with basic properties is known. 

Because of the multitude and diversity of iodonium salts and zwitterions, some of which are labile or are prepared for specific purposes, their preparative methods are discussed in Chapter 8, for diaryl iodonium salts and related compounds, Chapter 9 for perfluoroalkyl, alkenyl and alkynyl phenyliodonium salts and Chapter 10 for zwitterionic iodonium compounds. In addition, the preparation of some lesser known reagents, including 2-iodosylbenzoic acid, is given in Chapter 12. 

The 127I NQR spectra of an extensive series of iodonium compounds, [R2I]+BF, have been reported52,53. In addition to the fact that iodine is the only halogen that forms an extensive series of halonium compounds, the study of 127I has the advantage that, since its spin is equal to 5/2, there are two transitions and therefore both the coupling constant and the asymmetry parameter may be obtained. This is particularly important for a polycoordinated nucleus, since we may anticipate that the asymmetry parameter will be far from negligible. A selection of the NQR parameters for these compounds is shown in Table 9. Also studied were the iodonium halides, whose structures differ from those of the... 

Finally, various iodonium compounds, mono- and bisalkynyliodonium salts among them, have recently been found to be inhibitors of the redox cofactor methoxatin (PQQ)114. 

The production of 1-chloro-l-decyne and 1 -chloro-3- -pentylcyclopentene from the former iodonium compound and 1-bromo-l-decyne from the latter cannot be accounted for by the a-elimination mechanism. 

DIPHENYLIODONIUM IODIDE (Iodonium Compounds, diphenyl—iodide)... 

Primary vinyl iodonium compounds (1, = H) are readily prepared as... 

The basic triethylamine promotes an ionic reaction leading to the diazo compound (32), which then reacts with iodine in tetrahydrofuran probably through the iodonium compound (23) to give the iodo-product (24. Steroidal 17- and 20-hydrazones give the vinyl iodides (25) and (26) respectively. 

In 2004, Kumar and Montanari introduced a fluorous tagged trivalent iodonium compound that can be used as a tag for /-Boc based solid phase peptide synthesis by tagging free amines with a perfluoroheptyl (W-C7F15) group.It is an efficient fluorous tagging reagent that has the potential to help in the synthesis of both routine and difficult peptide and protein sequences. The... 

Iodonium Hydroxide.—These iodonium compounds are considered as derivatives of a hypothetical base, H2l(OH), iodonium hydroxide, as above. 

We note later some cations containing exclusively halogen atoms. Iodine also forms ions (R-I-R)" in which the groups R are usually aromatic radicals (Ar). The halides (Ar-I-Ar)X are not very stable, but the hydroxides are strong bases, proving dissociation to (Ar-I—Ar) ions. These iodonium compounds are the analogues of ammonium and sulphonlum compounds ... 

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