Alkanes, addition halides

A soluble dendritic Ni catalyst for the atom-transfer radical addition (ATRA, i.e., polyhalogenated alkane addition to olefins, the Kharasch addition) was described by van Leeuwen and van Koten et al. in 1994 [17]. GO and G1 carbosilane den-drimers, fimctionalized with NGN pincer-nickel(II) groups, were synthesized and applied as homogeneous catalysts for the addihon of organic halides to alkenes [Eq. (7)]. 

Their physieal properties are essentially those of the alkanes. It is the unsaturated linkages that dominate the ehemistry and the main reaetion is one of addition (e.g. hydrogen, halogen, and hydrogen halides) aeross the double bond to produee saturated eompounds. This reaetivity is utilized in the manufaeture of long-ehain polymers, e.g. polyethylene and polypropylene. 

In another reductive coupling, substituted alkenes (CH2=CH Y Y = R, COOMe, OAc, CN, etc.) can be dimerized to substituted alkanes (CH3CHYCHYCH3) by photolysis in an H2 atmosphere, using Hg as a photosensitizer. Still another procedure involves palladium-catalyzed addition of vinylic halides to triple bonds to give 1,3-dienes. ... 

Alkenes undergo addition reactions with hydrogen to form alkanes, with halogens to form dihaloalkanes, with hydrogen halides to form monohaloalkanes and with water to form alcohols. For example ... 

Other methods for the preparation of alkyl halides are electrophilic addition of hydrogen halides (HX) to alkenes (see Section 5.3.1) and free radical halogenation of alkanes (see Section 5.2). 

C-Alkylations have been performed with both support-bound carbon nucleophiles and support-bound carbon electrophiles. Benzyl, allyl, and aryl halides or triflates have generally been used as the carbon electrophiles. Suitable carbon nucleophiles are boranes, organozinc and organomagnesium compounds. C-Alkylations have also been accomplished by the addition of radicals to alkenes. Polystyrene can also be alkylated under harsh conditions, e.g. by Friedel-Crafts alkylation [11-16] in the presence of strong acids. This type of reaction is incompatible with most linkers and is generally only suitable for the preparation of functionalized supports. Few examples have been reported of the preparation of alkanes by C-C bond formation on solid phase, and general methodologies for such preparations are still scarce. 

NiCRA-bpyA NiCRA complex containing 2,2 -bipyridine (bpy) effects homocoupling of aryl halides (Ullmann coupling), often in high yield, which can be improved in some cases by addition of KI or Nal. When used in a catalytic amount, reduction to an alkane is the main side reduction. 

These reagents are useful in the 1,4-addition of alkyl groups to a,(l-unsaturated carbonyl systems and can also be reacted with alkyl halides to produce larger alkanes (Following fig.). The mechanism is considered to be radical based. 

Reaction (414) is formally analogous to the oxidative addition of alkyl halides to noble metal complexes described earlier, and both homolytic and heterolytic processes can be envisaged. Heterolytic cleavage of C—H bonds represented in Eq. (415) is analogous to the interaction of the powerful oxidant Co3+ with alkanes in TFA in reaction (229). 

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