Halides alkyl transfer with

Radicals for addition reactions can be generated by halogen atom abstraction by stannyl radicals. The chain mechanism for alkylation of alkyl halides by reaction with a substituted alkene is outlined below. There are three reactions in the propagation cycle of this chain mechanism addition, hydrogen atom abstraction, and halogen atom transfer. 

Electrogenerated monovalent Co complexes of the well-known open chain N202 Schiff base ligands salen (8), salphen (9), and their substituted derivatives undergo oxidative additions with alkyl halides. Reactions of the complex with substrates within the series RBr (R = Pr, Bu, t-Bu) proceed at different rates. The reaction occurs by an inner-sphere alkyl-bridged electron transfer, with a Co1- R+- X-transition state, which is sensitive to distortions of the complex in different configurations.124... 

Several approaches have been used to overcome the stereochemical difficulties for intramolecular "alkyl transfer." One of these is to use a "trapping agent" in the reaction mixture with which the oxyanion site of the intermediate can react. A silyl halide works nicely for this purpose the halide anion facilitates the required dealkylation.206-210... 

From the radioactivity of the polymer and of the original methyl chloride it was found that if there was not more than one 14C atom per polymer molecule, 0.27 of the polymer molecules contained a methyl group derived from the solvent. The authors concluded that the formation of this fraction of molecules had been started by initiation according to equation 10, and that the remainder had been started by transfer with monomer. It has been admitted by the authors (private communication, and in press) that this conclusion is not warranted on this evidence, since alkyl halides such as methyl chloride, are known to act as transfer agents by a reaction which can be represented by Equation 7. At best, the evidence shows that methyl chloride was involved in starting - by initiation and/or transfer - about a quarter of the polymer molecules. The results of further studies with 14CH3C1 and CH336C1 are in process of publication [12]. 

Fig. 5 Marcus plot of electron transfer reductions of alkyl halides, as contrasted with archetypal SN2 substitution processes (Finkelstein reactions, circled see Eberson,...

One final example worth mentioning is the reductive alkylation/arylation with lithium and alkyl/aryl halides in liquid ammonia. This is a two-step process in which negatively charged nanotubes are formed via electron transfer from the metal. This step is relatively easy and fast due to the CNTs electron sink properties, and it enables exfoliation of the tubes through electrostatic repulsion in the second stage, the alkyl/aryl halides react with the charged tubes to form a radical anion which can dissociate into the alkyl radical and the halide anion, with the former species undergoing addition to the CNT sidewalls [42]. 

In these reactions (Scheme 3.1), the first electron addition is to the alkene giving a radical-anion. This interacts with the alkyl halide to transfer an electron, in a process driven by simultaneous cleavage of the carbon-halogen bond. The alkyl radical formed in this manner adds an alkene radical-anion [25]. Aluminium ions generated at the anode are essential to the overall process. They coordinate with the intermediate carbanion, which then interacts with the second halogen substituent in an Sn2 process to form the carbocycle. 

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