Iodinating agents

Molecular iodine is not a very powerful halogenating agent. Only very reactive aromatics such as anilines or phenolate anions are reactive toward iodine. Iodine monochloride can be used as an iodinating agent. The greater electronegativity of the... 

Sulfuryl chloride alone, or in the presence of silicon dioxide or disulfur dichloride-aluminium chloride, gave the 5-chloro derivatives of 2-perhalogenomethylthiopyrroles, along with some di-substituted (3,5- and 4,5-) and tri-substituted (3,4,5-) compounds. Brominating and iodinating agents reacted similarly (85JHC281). 

Such anti-MarkownikofT regioselectivity may be achieved in the formation of iodides by proceeding via the corresponding organoborane, which is then decomposed with iodine in the presence of sodium methoxide93 (Expt 5.66). More recently iodine monochloride has been found to be an economic alternative iodinating agent.94... 

Recently, the reaction of masked ortho-benzoquinone [92] with C60 was tested [93]. The [4+2] cycloaddition reaction of such electron-deficient dienes with fullerenes resulted in the formation of highly functionalized bicyclo [2.2.2] octenone-fused fullerenes. The reactants were generated in situ by the oxidation of the readily available 2-methoxy phenols with hypervalent iodine agents. For the several different masked ortho-benzoquinones that were tested, it was found that the yield of the cycloadducts depends on the nature of the starting materials and the reaction conditions. Other Diels-Alder reactions of such electron-deficient dienes with electron-poor fullerenes involved tropones [94], 1,3-butadienes substituted with electron-withdrawing groups [95], and 2-pyrone [96]. 

Doak and Corwin94 have studied the kinetics of the iodination of some trisubstituted derivatives of pyrrole and A-methylpyrrole. Both free iodine and hypoiodous acid are supposed to be the iodinating agents in this reaction. The similar reactivity exhibited by pyrrole and A-rn ethyl py rrole contradicts the hypothesis previously proposed,95 that the great reactivity of pyrroles in iodination may be due to a reaction either of the dissociated anion or the pyrrolenine tautomer. 

Perhaloalkanes serve as bromination or iodination agents in the radical decarbox-ylative halogenation of carboxylic acids. In an interesting modification of the Hunsdiecker-Bodin reaction Barton and coworkers have applied iV-hydroxypyridine-2-thione esters as nonelectrophilic intermediates for the decarboxylative bromination and iodination of primary, secondary and tertiary aliphatic and alicyclic592, as well as aroma-... 

PhI(OTf)2, NaI04, peroxyacetic acid, H2O2 peroxydisulfates, and ammonium iodide with Oxone . The ICl is a better iodinating agent than iodine itself. Among other reagents used have been IF (prepared directly from the elements), and benzyltrialkylammonium dichloroiodate (which iodinates phenols, aromatic amines, and A-acylated aromatic amines, as well... 

A(-Chloro- and Af-bromo-pyrazoles are unstable compounds, whilst (V-iodopyrazoles are stable (Section 4.04.2.1.3(xii)). These last compounds readily yield the iodonium ion, which in turn acts as an iodinating agent. Thus, the formation of 3-iodo-4,5-dimethylpyrazole from l-iodo-4,5-dimethylpyrazole (b-76MI40402) is explained. The different steps in the chlorination of 3,5-diphenylpyrazole have been characterized (Scheme 45). The iV-chloro derivative (533) was fairly stable when stored at low temperatures, but it was converted into the isopyrazole (534) on standing for several hours at room temperature (80JOC76, 82S844). 

Adverse reactions to intravascular iodinated agents are usually classified as minor, intermediate, or severe life-threatening. All types of reactions to low-osmolar contrast media are five times less common than reactions to high-osmolar contrast agents (SEDA-22, 489) (SEDA-23, 494) (SEDA-24, 519), and very severe adverse reactions to contrast media are rare, with a frequency of about 0.04% with high-osmolar agents and 0.004% with low-osmolar agents. However, there are no important differences in the safety profiles of the different low-osmolar non-ionic monomers (18). 

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