Termination reactions, radicals overview

The use of free-radical reactions in organic synthesis started with the reduction of functional groups. The purpose of this chapter is to give an overview of the relevance of silanes as efficient and effective sources for facile hydrogen atom transfer by radical chain processes. A number of reviews [1-7] have described some specific areas in detail. Reaction (4.1) represents the reduction of a functional group by silicon hydride which, in order to be a radical chain process, has to be associated with initiation, propagation and termination steps of the radical species. Scheme 4.1 illustrates the insertion of Reaction (4.1) in a radical chain process. 

The great majority of radical cascades involve sequences of intramolecular steps where the overall propagation is a unimolecular process (with the exclusion of the initiation and termination steps), and recent overviews are given in Refs 1-5. However, meanwhile many tandem reactions involving both intra- and intermolecular steps, as well as multicomponent tandem reactions, have been reported in the literature, which are compiled in recent reviews. " ... 

Table 20.1 Overview of the different steps of a radical polymerization, initiation, propagation, and termination— the chemical equation and rates of reaction steps R re-listed...

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