Maikovnikov addition

Although HI addition to alkenes and alkynes is faster than that of the other hydrohalides and free radical anti-Maikovnikov additions are not a problem, this reaction has received less attention than the others.173 The hydroiodination of alkenes is most commonly run using concentrated HI in water or acetic acid at or below room temperature. While the early literature suggests that simple terminal alkenes afford small amounts of anti-Markovnikov products, only Markovnikov products have been reported in the more recent literature (equations 125-129).67 176-179... 

The addition of a single-bonded reagent across a multiple bond is one of the fundamental reactions of organic radicals. The basic principles of this reaction were first advanced by Kharasch in pioneering studies on the mechanism of the peroxide-initiated anti-Maikovnikov addition of hydrogen bromide to alkenes.1 In the atom transfer method, the generation and removal of radicals are coupled and occur in the key atom transfer step. Compared to other methods, the atom transfer method provides unique options for synthetic reactions. But there are also important limitations. Recently, there has been a renewed interest in the application of the characteristics of atom transfer reactions in synthesis and new developments have been reviewed.5,161... 

Diethylphosphoryl azide gives an Mo-triazoline with noibomene subsequent photolysis gives the phosphorylated aziridine, but pyrolysis gives the imine isomer. Maikovnikov addition of diethyl dibro-mophosphoramidate to alkenes (BF3 catalysis) occurs in high yield the initial adducts were converted to IV-unsubstituted products but would be readily convertible to phosphorylated aziridines ty the Gabriel method.In any case, IV-unsubstituted aziridines are readily phosphoiylated. > ... 

Selenosulfonates (see also Section 3.6.2.3) add to alkenes when catalyzed by Lewis acids. These adducts are transformed via oxidative elimination to vinyl sulfones in good overall yields. Similar to other methods only trans addition is observed. Mixtures of regioisomers are often produced with unsyminetri-cal unactivated alkenes. All other alkenes (i.e. styrene and acrylonitrile) provide Maikovnikov additions. Radical processes yield anti-Markovnikov adducts. Thus, either regioisomeric vinyl sulfone may be prepared from almost any activated alkene by simply varying the mode of addition. ... 

In the presence of sodium methoxide, trifprimaTy alkyl)boranes wacX smomfaly to yield 3 mol equiv. of iodoalkam. In the presence of sodium hydroxide, two C—bcmds of tii(primary aIkyl)boranes are cleaved to the corresponding iodides.In the same conditions tri(secondaiy alkyl)boranes react significantly more slowly and only one C—B bond is broken.For anti-Maikovnikov addition of HI to terminal alkenes the inocess shown in equation (60) is therefore licable. ... 

Xu J. M. et al. [95] in 2006 described the Maikovnikov addition of A/ -heterocycles to viityl esters using IL, i.e., l-methyl-3-butylimidazolium hydroxide ([bmimjOH) catalyst (Scheme 7.2). 

In the presence of peroxides, the reagent that attacks the double bond first is the larger bromine atom. It attaches itself to the less hindered carbon atom by a radical mechanism, so as to form the more stable radical intermediate. The result is anti-Maikovnikov addition. Nonpolar solvents are preferable for reactions involving radicals. 

In addition to the intermolecular hydroamination reactions, a significant number of intramolecular versions have been developed. As an example, the palladium-catalyzed cyclization of aUcynylamides generated alkylidene lactams in moderate to good yield (Scheme 3.136) [146], The reactions were quite rapid and afforded formal Maikovnikov addition products. 

HX Hydrohalogenation Treatment with an alkene gives a Maikovnikov addition of H and X across the alkene. 

BHs THF 2) H2O2, NaOH Hydroboration- oxidation Treatment with an alkene gives an awft-Maikovnikov addition of H and OH across the alkene. The reaction proceeds exclusively via a s)m addition. 

During the addition step, we must use a reaction that gives an awh-Maikovnikov addition (such as hydrobromination in the presence of peroxides). During the elimination step, we need the Hofmann product (less substituted alkene), so we use teri-butoxide as the base. The entire synthesis is shown here ... 

This alkyne can be made from the starting alkene via an awtf-Maikovnikov addition of HBr, followed by treatment with the appropriate alkynide ion, as shown... 

This secondary alcohol can be made from the starting alkene via a Maikovnikov addition of H and OH. In this case, we caimot perform an acid-catalyzed hydration, as a carbocation rearrangement would likely occur (the initially formed secondary carbocation could undergo a methyl shift to give a more stable tertiary carbocation). To avoid a carbocation rearrangement, we must use oxymercuration-demercuration. 

---