Iodination of alkenes

Iranpoor, N., Shekarriz, M. Regioselective 1,2-alkoxy, hydroxy, and acetoxy iodination of alkenes with I2catalyzed by Ce(S03CF3)4. Tetrahedron 2000, 56, 5209-5211. 

Iodination of Alkenic Compounds. lodolactonization and related reactions with alkenes can be achieved using NIS in apro-tic solvents. In addition, iodoesters may also be prepared by the reaction of alkenes with NIS in the presence of carboxylic... 

Little can be said about the mechanisms of fluorination or iodination of alkenes by the molecular halogens. Fluorine reacts violently with alkenes, giving mixtures including products resulting from degradation of the carbon chain. There have been few mechanistic studies of the reaction with iodine. One significant feature of the reaction is its reversibility. Some iodine remains in equilibrium with simple alkenes. 

For many experimental conditions, the mechanism in Scheme 10.3 is a simplification. This mechanism typically occurs only at low concentrations of bromine or in water and alcohol solvents. In solvents of lower polarity, even acetic acid, the reaction is second order in bromine. The second bromine assists the first step by polarizing the bromine that is adding to the alkene, creating Bra" instead of Br" as a leaving group (Eq. 10.20). Similarly, iodinations of alkenes are commonly second order in I2, and sometimes even third order. Kinetic expressions such as that given in Eq. 10.21 are often observed. The kinetic dependence on Bra" indicates a reaction between the alkene and Br2, as well as Br, which is equivalent to Bra". 

Bortolini, O., Bottai, M., Chiappe, C., Conte, V and Pieraccini, D., Trihalide-based ionic liquids. Reagent-solvents for stereoselective iodination of alkenes and alkynes. Green Chem. 4, 621-627 (2002). 

Type of reaction C-I and C-Nu bond fomaation Reaction conditions Acetonitrile, room temperature Synthetic strategy Co-iodination of alkenes Catalysts (Diacetoxyiodo)benzene/iodine... 

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). 

PREVOST - WOODWARD OlefinHydroxylation CMunctlonalization of alkenes wtfh iodine and silver (or sodium] cart)Oxylates. 

Replacement of silver nitrite by inexpensive sodiiunor potassium nitrite enhances the imlity of this process Treatment of alkenes v/ith sodiiun nitrite and iodine in ethyl acetate and water in the presence of ethylene glycol gives conjngatednitroalkenesin49-82% yield The method for generation of nitryl iodide is improved by the treatment of iodme v/ith potassium nitrite complexed v/ith 18-crovm-6 in THF under sonicadon, as shovmin Eq 2 32 ... 

Addition of iodine to alkenes can be accomplished by a photochemically initiated reaction. Elimination of iodine is catalyzed by excess iodine, but the diiodo compounds can be obtained if unreacted iodine is removed.52... 

The synthetic applications of this reagent to the synthesis of nitroalkenes have been known since the 1960s.60 Nitration of alkenes with nitryl iodide, generated in situ from iodine and silver nitrite, is convenient for the synthesis of P-nitrostyrenes with various functional groups.61 This method is applied to the synthesis of ortho-methoxylated phenylisopropylamines, which are potent serotonine agonists (Eq. 2.31).62... 

The synthesis and properties of heat-resistant polyazomethines containing 2,5-disubstituted oxadiazole fragments, being insulators convertible into semiconductors by doping with iodine, have been described. The radical copolymerization of alkenes with the fluorescent co-monomer 2-/-butyl-5-(4 -vinyl-4-biphenylyl)-l,3,4-oxadiazole has resulted in useful macromolecular scintillators. Anionic polymerization of 2-phenyl-l,3,4-oxadiazolin-5-one has produced a nylon-type product <1996CHEC-II(4)268>. 

Negishi previously reported that a wide variety of Lewis-acidic compounds catalyzed hydrozirconation of alkenes such as 1-decene 108 with /-BuZrCp2Cl.126 It was found that the reaction of 1-decene with 1.1 molar equiv. of TIB A, in the presence of 2-5 mol% of chlorine-containing late transition metals, led to the formation of 1-iododecane 110 after treatment of the product with iodine (Table 9). 

Regiospecific hydrocyanation of alkenes. Reaction of /-butyl isocyanide with the adducts of 1 with alkenes results in products (2) that are converted by iodine (excess) into hydrocyanides (3) and /-butyl iodide with release of ClCp2ZrI. (CH1).,SiN=C can be used in place of (CH,)3CN=C, but yields are generally lower.2... 

Bis(pyridinium)iodonium tetrafluoroborate [I(Py)2BF4] reacts readily with alkenes to afford 1,2-disubstituted products arising from addition of iodine and pyridine. Synthetically more important is, however, the reaction of unsaturated systems with I(Py)2BF4 in the presence of nucleophiles, which provides a general method for vicinal iodofunction-alization of alkenes. In this regard, the addition of a stoichiometric amount of tetrafluo-roboric acid to the reaction medium is often required to avoid the competitive formation of products resulting from pyridine acting as a nucleophile. 

The transfer of iodine to the organic substrate represents a formal reductive elimination at tellurium(lV) to give tellurium(ll) as well as oxidation of the alkene. In a series of diaryltellurium(lV) diiodides, iodination of organic substrates is accelerated by electron-withdrawing substituents and is slowed by electron-donating substituents, which is consistent with the substituent effects one would expect for... 

Iodine was found to be an efficient catalyst for the aziridination of alkenes (Scheme 6) utilizing chloramine-T (A-chloro-A-sodio-p-toluenesulfonamide) as the nitrogen source. For example, when 2 equiv. of styrene (45a) were added to chloramine-T in the presence of a catalytic amount of iodine (10mol%) in a 1 1 solvent mixture of acetonitrile and neutral buffer, the corresponding aziridine (46) was obtained in 91% yield. The reaction proved to work with other acyclic and cyclic alkenes, such as oct-l-ene and cyclohexene. The aziridination of para-substituted styrene derivatives (45b-e) demonstrated that, as expected for an electrophilic addition, electron-rich alkenes reacted faster than electron-poor alkenes. However, with 1 equiv. of I2, mainly iodohydrin (47) was formed. A catalytic cycle has been proposed to account for the fact that only a catalytic amount of iodine is required (Scheme 1) ... 

A mixture of silver nitrite and iodine reacts with alkenes to give jS-nitroalkyl iodides, and therefore, provides a convenient route to a-nitroalkenes. Treatment of alkenes with ammonium nitrate and trifluoroacetic anhydride in the presence of ammonium bromide, followed by... 

The Sbarpless asymmetric dihydroxylation of alkenes usually employs a stoichiometric amount of iodine or potassium ferricyanide to re-oxidisc the osmium centred intermediates in the catalytic cycle [73]. Either reagent can also be used in catalytic amounts and re-oxidised electrochemically at an anode [74, 75]. 

Cyanogen Iodide (ICN) has been used extensively for the cyanation of alkenes and aromatic compounds [12], iodination of aromatic compounds [13], formation of disulfide bonds in peptides [14], conversion of dithioacetals to cyanothioacetals [15], formation of trans-olefins from dialkylvinylboranes [16], lactonization of alkene esters [17], formation of guanidines [18], lactamization [19], formation of a-thioethter nitriles [20], iodocyanation of alkenes [21], conversion of alkynes to alkyl-iodo alkenes [22], cyanation/iodination of P-diketones [23], and formation of alkynyl iodides [24]. The products obtained from the reaction of ICN with MFA in refluxing chloroform were rrans-16-iodo-17-cyanomarcfortine A (14)... 

Iodofluorination and bromofluorination of alkenes are also effected in hydrogen fluoride systems by using bromine or iodine with an equivalent amount of silver(I) nitrate. In some cases, iodofluorination can also be achieved by iodine without adding the silver(I) salt, as illustrated in the following procedure. 

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