Iodine reaction with alkenes

Preparation of Iodine Monofiuoride and Its Reactions with Alkenes General Procedure 4... 

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... 

What about diatomic fluorine, F-F For many years, elemental fluorine was thought to be too reactive and too dangerous for reaction with alkenes. To void such problems, fluorine is typically mixed with an inert gas such as nitrogen or argon. Diluted in this manner, fluorine does react with alkenes, but the yields are often poor and, in some cases, solvents for the alkene, such as methanol, participate in the reaction. 1-Phenylpropene (PhCH=CH2), for example, reacted with fluorine in methanol to give 51% of the corresponding difluoride, along with 49% of 2-fluoro-l-methoxy-l-phenylpropane. The problems associated with fluorine lead to a simpliflcation. In this chapter, alkene reactions are reported only for chlorine, bromine, or iodine but not fluorine. 

The above reactions of carboryne with alkenes and alkynes are mediated by a stoichiometric amount of the Ni reagent. In view of the fact that benzyne can undergo Ni-catalyzed reactions with alkenes and/or alkynes [19], carboryne is expected to produce a catalytic cycle by making use of the Ni(0) species generated from the reductive elimination step of the above process. l-Iodo-2-lithiocarborane is chosen as the carboryne precursor, as it can be conveniently prepared in situ from the reaction of dilithiocarborane with 1 equiv of iodine at room temperature and is much more thermally stable than... 

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). 

Stereoselective syntheses of trisubstituted alkenes are based on E- and Z-alkenyldioxaborinanes. Reaction with an alkyllithium reagent forms an ate adduct that rearranges on treatment with iodine in methanol.31... 

Both alkynes and alkenes can be obtained from adducts of terminal alkynes and boranes. Reaction with iodine induces migration and results in the formation of the alkylated alkyne.32... 

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. 

When the reaction of methyl 5,6-dideoxy-2,3-di-0-p-tolylsulfonyl-a-L-arafoino-hex-5-enofuranoside with silver nitrite and iodine was performed in more-polar solvents, such as methanol and acetonitrile, a /3-iodo nitrate was produced, in addition to the C-iodo-C-nitro adduct 88 in methanol, the ratio of the two products was130 3 2. The /3-iodo nitrate was identical with the adduct obtained by the reaction of the alkene with silver nitrate and iodine in acetonitrile.132 The formation of the /3-iodo nitrate in the silver nitrite-iodine reaction in polar solvents may be due to the increased solubility of the silver nitrite the available nitrite ions could then be oxidized to nitrates. The positions of the iodo and nitrate groups in the adduct have not yet been established. 

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