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

174 Consecutive Radical Reactions
Allylsilylation procedures of carbon–carbon and carbon–oxygen double
bonds under free-radical conditions have been established [86]. For example
the reaction of 72 with a variety of monosubstituted alkenes (R ¼ CN, CO2
Me, Ph, n-C8H 17, OBu, SPh) gives the corresponding allylsilylated products in
moderate to very good yields, whereas with maleic anhydrides high stereoselectivity
was observed. This methodology is also applicable to carbonyl derivatives
(Scheme 7.9). Similar experiments have been performed by replacing alkenes
with alkynes and the formation of bisallylic derivatives has been reported.
(TMS) 3 Si
R
R CO 2 Me
44-91%
(TMS) 3 Si
O
Ph H
(TMS) 3 Si O
72
CO 2 Me
Ph CO 2 Me
81%
Scheme 7.9 Allysilylation of unsaturated bonds
O
O
R
O
O
(TMS) 3 Si
7.7 APPLICATION TO TANDEM AND CASCADE RADICAL
REACTIONS
O
R
O
CO 2 Me
R = H, 89%
R = Me, 58%
The increasing popularity of radical reactions is certainly due to the so-called
‘tandem or cascade reaction’, i.e., the ability of forming and breaking several
bonds in a one-pot procedure. Again, the concepts of disciplined processes and
predictability are applied in these successful strategies, which show the elegance
and power of the synthetic plan based on radical reactions.
Two examples of three-components coupling reaction are shown in Reactions
(7.77) and (7.78) [27,87]. These radical chain reactions proceeded by the
addition of an alkyl or vinyl radical onto carbon monoxide, generating an acyl
radical intermediate, which, in turn, can further react with electron-deficient
olefins to lead, after reduction, to a formal double alkylation of carbon monoxide.
These three-components coupling reactions require the generation of
four highly disciplined radical species, which have specific functions during
the chain reaction.