Iodides arenes

Trimethylsilylarenes. Aryl chlorides and bromides on reaction with tri-methylsilylpotassium, trimethylsilylsodium, or trimethylsilyllithium (7, 400) are converted into trimethylsilylarenes in about 90% yield together with some of the product of reduction (ArH, 5-87 )- In the case of aryl iodides, arenes are obtained in about 25% yield. This trimethylsilyldehalogenation is probably a free-radical process. 

Chlorination is carried out m a manner similar to brommation and provides a ready route to chlorobenzene and related aryl chlorides Fluormation and lodmation of benzene and other arenes are rarely performed Fluorine is so reactive that its reaction with ben zene is difficult to control lodmation is very slow and has an unfavorable equilibrium constant Syntheses of aryl fluorides and aryl iodides are normally carried out by way of functional group transformations of arylammes these reactions will be described m Chapter 22... 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

The reaction of perfluoroalkyl iodides with electron donor nucleophiles such as sodium arene and alkane sulfinates in aprotic solvents results in radical addition to alkenes initiated by an electron-transfer process The additions can be carried out at room temperature, with high yields obtained for strained olefins [4 (equations 3-5)... 

Arylamines are converted by diazotization with nitrous acid into arenediazonium salts, ArN2+ X-. The diazonio group can then be replaced by many other substituents in the Sandmeyer reaction to give a wide variety of substituted aromatic compounds. Aryl chlorides, bromides, iodides, and nitriles can be prepared from arenediazonium salts, as can arenes and phenols. In addition to their reactivity toward substitution reactions, diazonium salts undergo coupling with phenols and arylamines to give brightly colored azo dyes. 

More recently, Curran and Keller found that the (TMSlsSiH-mediated addition of aryl iodides to arenes are facilitated by oxidative rearomatization with oxygen (Reaction 69). Here, AIBN is not necessary for good performance of the reaction. The reaction proceeds well in both inter- and intra-molecular (see above) versions. 

Denmark pursued intramolecular alkyne hydrosilylation in the context of generating stereodefined vinylsilanes for cross-coupling chemistry (Scheme 21). Cyclic siloxanes from platinum-catalyzed hydrosilylation were used in a coupling reaction, affording good yields with a variety of aryl iodides.84 The three steps are mutually compatible and can be carried out as a one-pot hydro-arylation of propargylic alcohols. The isomeric trans-exo-dig addition was also achieved. Despite the fact that many catalysts for terminal alkyne hydrosilylation react poorly with internal alkynes, the group found that ruthenium(n) chloride arene complexes—which provide complete selectivity for trans-... 

A wide range of olefins can be cyclopropanated with acceptor-substituted carbene complexes. These include acyclic or cyclic alkenes, styrenes [1015], 1,3-dienes [1002], vinyl iodides [1347,1348], arenes [1349], fullerenes [1350], heteroare-nes, enol ethers or esters [1351-1354], ketene acetals, and A-alkoxycarbonyl-[1355,1356] or A-silyl enamines [1357], Electron-rich alkenes are usually cyclopropanated faster than electron-poor alkenes [626,1015],... 

Asymmetric induction of between 30 and 66% has been reported for the addition of perfluoroalkyl iodides to chiral arene/chromiumtricarbonyl complexes using ultraso-nically dispersed zinc at room temperature (Scheme 3.19) [101], Photochemical decomposition of the organometallic intermediate affords a chiral alcohol product. The reaction is carried out in DMF as solvent and high overall yields are reported e.g.80 % (R = Et). Only a small excess of the perfluoroalkyl iodide is required and the conversion is complete in under 1 h. 

Dioxanes can be opened by an arene-catalyzed lithiation only if the carbon-oxygen bond to be cleaved occupies an allylic or benzylic position. This is the case of the vinyl-dioxane 416, which reacted with lithium and a catalytic amount of DTBB in THE at 0 °C, and the allylic intermediate 417 generated reacted at the y -position with tridecyl iodide to yield the compound 418, used in the synthesis of plasmenyl-type lipids (Scheme 117) . 

Finally, polymer 594 has been used as an arene-catalyst to activate nickel from nickel(II) chloride and lithium, in order to perform hydrogenation of different organic substrates such as afkenes, afkynes, carbonyl compounds and their imines, alkyl and aryl halides (chlorides, bromides and iodides), aromatic and heteroaromatic compounds as well as nitrogen-containing systems such as hydrazines, azoxy compounds or Af-amino oxides, giving comparable results to those obtained in the corresponding reaction in solution . 

An extension of this methodology, by hexafunctionalization of the arene group in 13 using ferrocenylbutyl iodide 14 under basic conditions, gave the hexafluoro-phosphate salt of the heptanuclear Fe(Il) complex cation 15 in 65% yield. Photolysis of 15, under similar conditions which converted 8 into 9, led to isolation of the neutral ferrocenyl complex 16 by selective decomplexation of the central... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

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