Iodine groups with

Kitamura et al. have developed (phenyl)[2-(trimethylsilyl)phenyl]iodomiim triflate (7) as an excellent benzyne precursor [13], possessing the hypervalent iodine group with a salient leaving ability ( 10 times greater than that of the OTf group). Treatment of 7, which is prepared in two steps from 1,2-dichlorobenzene, with TBAF efficiently generates benzyne (1) (Scheme 12.7). 

It is also interesting to note that quatemization of a chloropyrimi-dine at the nitrogen atom adjacent to the chloro group with methyl iodide results in the easy replacement of the chlorine by iodine, whereas similar salt formation on the remote nitrogen either leaves the chlorine unaffected or replacement occurs only at higher temperatures. A similar reaction occurs between 2-amino-6-chloro-4-methylpyrimidine and dimethyl sulfate in nitrobenzene to give the salt 45 and betaine 46. ... 

The oxygen atom at 21 is similarly an expendable group. Reaction of 241 (obtained from 185 by the usual procedure for introduction of the 9a-fluoro group) with methanesulfonyl chloride affords the 21 mesylate (242a). Replacement of the leaving group at 21 with iodine by means of potassium iodide in acetone followed by reduction of the halogen with zinc in acetic acid leads to fluorometholone (243). ... 

The determination is done by oxidation of the -SH group with 0.1N iodine solution in NaHCC>3 solution visually with respect to strength or potentiometrically (the equivalence point is difficult to recognize) or in NaOH solution potentiometrically, which is more favorable. The error of the method for a weight of lOmg amounts is approximately 0.5%. 

Theory The estimation of analgin depends upon the oxidation of the enolic group with iodine. The reaction is not reversible ... 

Fig. 12. Structures of iodinated triglycerides with two triiodobenzene groups [71]... 

Addition of another hydroxyl group at C21 is accomplished by subsequent bromina-tion of a methyl group with molecular bromine, replacing the bromine atom with iodine, and reacting iodide with potassium acetate, which forms the corresponding acetoxyketone... 

Chlorosulfate groups can be readily removed to give the corresponding hydroxyl groups, with retention of configuration, by treatment of a solution of the carbohydrate chlorosulfate in methanol with sodium iodide in aqueous methanol24 immediate liberation of iodine and evolution of sulfur dioxide occur.34 A possible mechanism for the dechlorosulfation reaction involves displacement by iodide at the chlorine atom the initially formed iodine monochloride would react with iodide ion to give iodine and chloride ion. Alternatively, an unstable iodosulfate could be formed as an intermediate.35... 

Treatment of /3,-y-unsaturated acids with iodine in sodium bicarbonate solution may give y-iodo-/3-lactones in good yield (equation 94), but if potassium iodide is added then /3-iodo-y-lactones are produced. One compound, 4-phenyl-3-butenoic acid, gave the y-lactone even when KI was not present, presumably due to the phenyl group favoring development of carbonium ion character at C-4 in the intermediate iodine complex. With... 

Iodine pentafluoride reacts quantitatively with perfluoro(trifluorOsilyl)benzene in acetonitrile at 20"C in the absence of pyridine to yield (pentafluorophenyl)iodine tetrafluoride.133 Alk-oxysilanes were used to replace fluorine atoms in iodine pentafluoride with alkoxy groups.135136... 

---