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

Silylated Cyclohexadienes 81
and (4.76), which show that these reactions work well also with different
substituted silyl moieties.
O
Br
i-Pr3Si MeO
AIBN, 70 �C
OMe
t-BuMe2Si MeO OMe
PhSe OH
OH
AIBN, 70 �C
63%
76%
O
(4.75)
(4.76)
Scheme 4.8 shows that the CH2 of cyclohexadiene moiety acts as the H donor
with formation of cyclohexadienyl radical as the intermediate, which rapidly
ejects the silyl radical upon re-aromatization. The silyl radical is able to propagate
the chain by reaction with a starting halide. The hydrogen donation of
silylated cyclohexadienes toward primary alkyl radicals is reported to be
1 10 5 M 1 s 1 at 70 8C [120], which is in accord with the reported range of
10 3 –10 4 M 1 s 1 at room temperature for the reaction of primary and secondary
alkyl radicals with differently substituted cyclohexadienes [121].
RH
Me SiR' 3
MeO OMe
H H
Me SiR'3
MeO OMe
H
R
R' 3 SiX
R' 3Si
MeO
Scheme 4.8 Silylated cyclohexadienes as radical-based reducing agents
RX
Me
OMe