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

Intramolecular Formation of Carbon–Carbon Bonds (Cyclizations) 151
Using this procedure for the secondary isocyanide 7 (Reaction 7.14), the
desired product was isolated after workup in 78 % yield as a 4.6:1 mixture of
cis and trans isomers [7].
Ph
7
NC
(TMS) 3SiH AIBN, 70 �C
+
Ph Ph
78% (4.6:1)
(7.14)
The behaviour of a series of methyl substituted hept-6-en-1-yl radicals,
generated from the corresponding iodides with (TMS) 3SiH and AIBN in benzene
at 80 8C, has been investigated too. The low regioselectivity and poor
stereoselectivities observed for these reactions are not unexpected given the
conformational flexibility inherent in the hept-6-en-1-yl radical [24].
Five-membered ring formation has been used for preparing fused cyclic compounds,
such as functionalized diquinanes [25] by the reaction of 8 with
(TMS) 3SiH under normal conditions. The expected product 9 was isolated in
80% yield and in a a: b ratio of 82:18, as the result of a kinetic controlled reaction.
In Reaction (7.15), silyl radicals effect the PhSe group removal and generate the
tertiary alkyl radical, which gives cyclization by adding to the double bond. The
b-elimination of PhS: radical and the silane trapping of the thiyl radical complete
the radical chain.
H
O
SePh SPh
8
SPh
(TMS) 3SiH
AIBN, 90 �C
O
+
SPh
O
9, 80% (α:β = 82:18)
A convenient route to triquinanes is based on a strategy of silyl radical
addition to conjugated dienes to form allylic type radicals and their subsequent
intramolecular addition to C C double bonds. By exposure of 10 to
w
(TMS) 3SiH and AIBN at 80 8C (Reaction 7.16) the triquinane 11 is obtained
with an unoptimized 51 % yield [26].
AcO
10
SPh
(TMS) 3 SiH
AIBN, 80 �C
AcO Si(TMS) 3
11, 51%
SPh
(7.15)
(7.16)