Iodine in functionalization

Iodine in functionalization of C 19 meth> 1 group of 3d acetoxy 20/3 hydroxy 5 pregnene 46, 58 Iron powder in preparation of ketones from carboxylic acids, 47, 75 Isobutene, 45, 49... 

The iodination reaction can also be conducted with iodine monochloride in the presence of sodium acetate (240) or iodine in the presence of water or methanolic sodium acetate (241). Under these mild conditions functionalized alkenes can be transformed into the corresponding iodides. AppHcation of B-alkyl-9-BBN derivatives in the chlorination and dark bromination reactions allows better utilization of alkyl groups (235,242). An indirect stereoselective procedure for the conversion of alkynes into (H)-1-ha1o-1-alkenes is based on the mercuration reaction of boronic acids followed by in situ bromination or iodination of the intermediate mercuric salts (243). 

Iodine. Of the 10—20 mg of iodine in the adult body, 70—80 wt % is in the thyroid gland (see Thyroid and antithyroid preparations). The essentiahty of iodine, present in all tissues, depends solely on utilisation by the thyroid gland to produce thyroxine [51-48-9] and related compounds. Well-known consequences of faulty thyroid function are hypothyroidism, hyperthyroidism, and goiter. Dietary iodine is obtained from eating seafoods and kelp and from using iodized salt. 

Figure 5. The Fourier transformed signal AS[r, i] of I2/CCI4. The pump-probe delay times are I = 200 ps, 1 ns, and 1 ps. The green bars indicate the bond lengths of iodine in the X and A/A states. The blue bars show the positions of the first two intermolecular peaks in the pair distribution function gci-ci- (See color insert.)...

People whose diets are sparse in seafoods are susceptible to iodine-deficiency diseases, which are easily prevented by providing iodine in the diet. Iodized salt, which contains 0.1% KI, performs this function. 

The basic function of the iodine in the iodonium bases, which correspond exactly to the ammonium, sulphonium, and oxonium bases, is most interesting. A molecule of diphenyliodonium iodide has the same atoms as two molecules of iodobenzene and decomposes on heating with liberation of heat (contrast other dissociations such as those of N204, NH4C1, PC15) into two moles of C8H8I. Test with a small sample in a tube. 

The convergent synthesis of a range of aryl ester dendrimers with peripheral tetrathiafulvalene units was also reported (Devonport et al. 1998). The dendrimers acquire some amount of the cation-radical tetrathiafulvalene tips on reacting with iodine in solutions. Another promising material is polyphenylene dendrimers functionalized with benzophenone units. On being transformed into the potassium ketyl derivatives, the dendrimers bring forth intermolecular biradicals. These technically attractive species contain four-membered cycles that coordinatively combine two potassium cations... 

Sodium iodide is an iodine supplement in food, an expectorant, cloud seed to cause rain, and solubilizes iodine in aqueous solution for analytical work. The radioactive iodide salt of sodium, Na(I-131) is used to diagnose thyroid function. 

Thyroid epithelial cells synthesize and secrete T4 and T3 and make up the functional units of thyroid glandular tissue, the thyroid follicles. Thyroid follicles are hollow vesicles formed by a single layer of epithelial cells that are filled with colloid. T4,T3, and iodine are stored in the follicular colloid. T4 and T3 are derived from tyrosyl residues of the protein thyroglobulin (Tg). Thyroid follicular cells synthesize and secrete Tg into the follicular lumen. Thyroid follicular cells also remove iodide (I ) from the blood and concentrate it within the follicular lumen. Within the follicles, some of the tyrosyl residues of Tg are iodinated, and a few specific pairs of iodoty-rosyl residues may be coupled to form T4 and T3. Thus, T4, T3, and iodine (in the form of iodinated tyrosyl residues) are found within the peptide structure of the Tg that is stored in the follicular lumen. 

Deficiency syndromes of Zn, Cu, Cr, Se and Mo have occurred in patients on total parenteral nutrition (TPN). There is still much research to be done in assessing the nutritional status of many elements and understanding their metabolism, so that normal dietary intake may be supplemented for health benefits. Table 2 is a summary of the amounts required, the functions and the nutritional (usually dietary) imbalances in humans, where known, of the essential trace elements.31-33 (Note that this summary does not attempt to include imbalances related to environmental toxicology and occupational hazards.) Several trace elements have important functions in the immune system. Some are associated with nucleic acid. Others have structural roles, such as Si in cartilage, F and Zn in bone. They may be parts of vitamins, such as Co in vitamin B12, or hormones, such as iodine in thyroid hormones, Zn and Cr have a role in the synthesis and action of insulin.31-33... 

Iodine, less reactive than bromine, is best added to alkenes by use of IC1 and IBr (see Section 1.8.3.3). Iodine itself adds rapidly but reversibly to alkenes forming diiodides by mechanisms that can be either ionic or radical. The position of the equilibrium depends upon the structure of the alkene, the solvent and the temperature. Simple vicinal diiodides survive distillation in the dark, but are unstable toward iodine or radicals. In the presence of functions containing free OH groups, such as alumina, HI generated from I2 adds to alkenes irreversibly with the result that the HI adduct, rather than the I2 adduct, is the exclusive product.86 A comparison of the reaction of 1,5-cyclooctadiene with chlorine, bromine and iodine in CH2CI2 reveals that chlorine gas at-50 C gives a 93 7 mixture of trans- and cis-5,6-dichlorocyclooc-... 

Radioactive isotopes of iodine are handled by the thyroid in the same way as stable iodine and are therefore actively concentrated, incorporated into thyroglobulin, stored, metabolized, and secreted as thyroid hormones. Small amounts of radioactive iodine are therefore ideal probes to analyse the uptake of iodine, the distribution of iodine in the gland, and possibly even its turnover and incorporation into thyroid hormones. Larger amounts of radioactive iodine selectively radiate the thyroid gland and therefore selectively impair the function of the follicular thyroid cells and eventually destroy them. 

The use of povidone-iodine for the treatment of burns, for peritoneal lavage in the treatment of purulent peritonitis, or as a rinsing solution for body cavities can increase serum iodine concentrations associated with increased urinary excretion of iodine. In people with burns the extent of iodine absorption depends on the extent of the burned body surface. It is not uncommon for serum iodine concentrations to rise to more than 1000 pg/ml. If renal function is intact, iodine elimination in the urine can be adequate. The serum iodine concentration returns to normal about 1 week after the last application. 

Reaction of an alcohol with the reagent o-phenylene phosphorochloridite followed by treatment of the alkyl o-phenylene phosphite so obtained with iodine in dichloromethane at room temperature results in a good yield of alkyl iodide. This method, exemplified by the preparation of 1-iodoheptane (Expt 5.60), is the preferred procedure when acid-sensitive functional groups are present. 

---