Replacement of iodine

Pentafluorobenzyl bromide [II] and a partially fluonnated alkyl iodide [12] react with potassium carboxylates An interesting replacement of iodine in a fluonnated alkyl iodide by an acetate group takes place with peroxyacetic acid [13] (equations 10-12)... 

Replacement of iodine in (perfluoroalkyl)ethyl iodides predominates over the usual conversion to olefins when the reagent is very nucleophilic and weakly basic Soft nucleophiles like sodium thiocyanate and sodium thiolates react well in displacements [46, 47] (equation 42)... 

Hydrogen iodide is easily eliminated by strong bases from perfluoroalky lethy 1 iodides to give terminal alkenes With perfluoroalkylpropyl iodides, however, replacement of iodine by nucleophiles predominates over the elimination reacUon [f] (equation 1)... 

Use of sodium sulfite allows selective replacement of iodine by hydrogen at C4 without affecting the ortho-position in 4-iodo-3-(2-iodophenyl)sydnone <2005SC639>. Acrylate groups attached at the C4 position of 4-arylsydnones reacted with guanidine hydrochloride but the result was replacement of the G4 substituent by hydrogen instead of formation of the planned pyrimidinone products <2003T4103>. 

Figure 6.2 Photoinduced replacement of iodine by phosphorus on an aromatic ring.

Reaction with the trimethylsylil derivative of acetylene in the presence of tetrakis-triphenylphosphine palladium leads to the replacement of iodine by the acetylide. Tributylammonium fluoride then removes the silyl protecting group to afford the kinase inhibitor erlotinib (78-7) [87]. 

By inspection one can see that the the 2R,3S and 2S,3R isomers are enantiomers and the 2R,3R and 2S,3S pair are enantiomers. As they are drawn, one can see the original E stereochemistry of the double bond. Thus the first pair comes from a stereospecific trans addition across the double bond while the second pair comes from a stereospecific cis addition. Clearly the stereochemistry of the double bond is maintained throughout the addition. Since iodine is the electrophile, a bridged iodonium ion is likely responsible. The initial addition gives only a single pair of enantiomers since the only nucleophile is benzoate. Also noted is that iodine is not in the product so something must replace the iodine. The silver ion would help to remove the iodine. Since iodine would cause a trans addition and the product has oxygens added trans, there must be a replacement of iodine by an... 

In the first example, nitration of the benzoate (140) with nitric acid affords the nitro derivative. Hydrogenation converts this to the anthranilate (141). In one of the standard conditions for forming quinazolones, that intermediate is then treated with ammonium formate to yield the heterocycle (142). Reaction of 142 with phosphorus oxychloride leads to the corresponding enol chloride (143). Condensation of 143 with m-iodoaniline (144) leads to displacement of chlorine and consequent formation of the aminoquinazoline (145). Reaction with the trimethylsilyl derivative of acetylene in the presence of tetrakis-triphenylphosphine palladium leads to replacement of iodine by the acetylide. Tributylammonium fluoride then removes the silyl protecting group to afford the kinase inhibitor erlotinib (146). ... 

The use of /t-iodotoluene difluoride for replacement of iodine by fluorine has beeen described as a nucleophilic displacement of IF2, as a good leaving group, in a pre-formed iodoaUcane difluoride [51]. Note that iodine is displaced in preference to p-TsO in this system (Figure 3.5a). 

In their inorganic compounds the three halogens chlorine, bromine and iodine are in this order in regard to their aflSnity for other elements. This seems to hold also in their organic compounds as shown by the replacement of iodine by bromine or chlorine, as given previously, and by the fact that alkyl iodides are the least stable or hemostreactive, while the chlorides are the most stable or the least reactive. This is illustrated by their action upon silver nitrate. Ethyl iodide acts with silver nitrate in alcoholic solution precipitating silver iodide even in the cold. 

The C—I bond is very unstable and more reactive than C—Br, C—Cl and C—F bonds. Iodine is the most expensive of the common halogens and is much less frequently used in synthesis than bromine, chlorine or fluorine. Organometallic reactions proceed with iodinated aliphatic or aromatic compounds more easily than with the other halogens. Noble metal catalysis with palladium complexes is most effective with iodinated compounds. A useful synthetic procedure is the facile reduction of iodinated derivatives under mild conditions. Replacement of iodine by hydrogen at an sp carbon is an exothermic reaction with A// = -25 kJ mol . ... 

This way of viewing molecular structure and chemical reactions bridged the two opposing theories of Berzelius and Dumas. Its success was extraordinary, as is well known For instance, hydrolysis of methyliodide was explained by dissociation of water in ions H+ and OH, followed by replacement of iodine (negative) by the OH ions ... 

Replacement of iodine, in the diiodo derivative 24 by sulfur, selenium, or tellurium also gives the corresponding heterocycles (25),97 while some heterocycles may be obtained directly from diiodotetrafluorobenzene (Scheme 697). 

Reactions. It is an excellent reagent for the selective replacement of iodine or bromine by methyl in a wide variety of substrates, as in examples cited by Corey and Posner 2... 

Replacement of iodine by bromine in this reaction leads to a mixture of cis-and fran -1-alkenyl bromides and the corresponding n-alkanal. After some experimentation, Hamaoka and Brown found that alkenylboronic acids can be converted into a-bromo dimethyl acetals by reaction with bromine and sodium methoxide in methanol at -78° ... 

Arl Ar-Ar. lodobenzene and para-disubstituted derivatives are converted into biaryls in about 50% yield when treated with a catalytic quantity of pal-ladium(II) acetate in triethylamine at 100°. Presence of water results in replacement of iodine by hydrogen. The reaction fails or proceeds in low yield with orf/zo-substituted aryl iodides. During the reaction Pd(0) is deposited. ... 

Replacement of iodine ortho to NH2, OH, COOH, COOEt, CONH2 or CSOEt is possible on reaction of the 2-substituted iodobenzene with diethyl hydrogenphosphonate". The 2-position is also sufficiently activated in the quaternary salts 247 [COOEt at C(4), C(5)... 

Irradiation sodium hydroxide I methanol Replacement of iodine by hydrogen... 

Electrochemistry of LB films of fullerenes has been widely studied and remains the subject of much research effort from both theoretical and experimental approaches. Bard etal. have studied basic electrochemistry of Ceo fullerene LB films on an electrode in acetonitrile solutions [23]. The study indicated that reduction of the fullerene films could form insoluble films with incorporated electrolyte cations or lead to dissolution. The study on Cgo LB films has become a focus of considerable interest however, it is difficult to fabricate high-quality LB films of pure Cgo due to its intrinsic hydropho-bicity. Kajiyama et al. applied a multistep creep method as an LB technique for constructing a fairly homogeneous Ceo monolayer, which is regularly packed in a hexagonal array [44]. Kunitake etal. developed the electrochemical replacement method to form epitaxial adlayers of fullerenes on Au(lll) surfaces [45]. The wet process method consists of the transfer of Langmuir films of fullerene onto iodine-modified Au(lll) surfaces at an air-water interface followed by the electrochemical removal and replacement of iodine adlayers with fullerene adlayers in solution. The fullerene adlayers prepared by this method showed excellent quality and uniformity. A visuahzing... 

Without additional reagents Replacement of iodine by alkoxyl... 

Silver acetate/potassium acetate/bromine Replacement of iodine by acetoxy groups with ring contraction... 

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