"Front Matter". In: Organosilanes in Radical Chemistry - Index of

7 Consecutive Radical Reactions
The use of free-radical reactions in multi-step synthesis has steadily increased
with time. Indeed, synthetic strategies based on radical reactions have become
more and more popular among chemists since a wide selection of functional
groups are now available to generate carbon-centred radicals [1]. The knowledge
of radical reactivity has increased to such a level as to aid in making the
necessary predictions for performing sequential transformations. The predictability
has extended to include also the formation of new stereogenic centres, so
to render radical reactions of special interest across the field of asymmetric
synthesis [1–4]. Stereoselectivities can be dictated by nearby stereocentres, by
chiral additives, and by chiral catalysts.
As far as the use of silanes as mediators in consecutive radical reactions is
concerned, the knowledge of their hydrogen donor abilities coupled with the
steric hindrance given by the silicon substituents has contributed substantially
in this area, with interesting results in terms of reactivity and stereoselectivity.
7.1 BASIC CONCEPTS OF CARBON–CARBON BOND FORMATION
The carbon-centred radical R: resulting from the initial atom (or group)
removal by a silyl radical or by addition of a silyl radical to an unsaturated
bond can be designed to undergo a number of consecutive reactions prior to H
atom transfer. The key step in these consecutive reactions generally involves the
inter- or intramolecular addition of R: to a multiple-bonded carbon acceptor.
Care has to be taken in order to ensure that the effective rate of the radical
addition is higher than the rate of H atom transfer. Standard synthetic planning
can be based on the knowledge of rate constants, and coupled with reaction
Organosilanes in Radical Chemistry C. Chatgilialoglu
# 2004 John Wiley & Sons, Ltd ISBN: 0-471-49870-X