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

76 Reducing Agents
RO
O
O
O
O
RO OC(S)OPh
S
O
O
NH
Ph
O
O
H H
Si
Si
H H
AIBN, 80 �C
Me H
Si
Si
HMe
AIBN, 80 �C
4.4.3 SILYL SUBSTITUTED SILICON HYDRIDES
RO
O
O
RO
O
96%
O
87%
O
O
O
(4.64)
(4.65)
Following the success of (TMS) 3SiH, a systematic investigation of organosilanes
having different silyl substituents at the SiH moiety has been carried out
with the aim of discovering other reagents and testing how to tune the reactivity
by the choice of substituents. The idea that they might be capable of sustaining
analogous radical chain reactions turned out to be correct. Indeed, the reductions
of organic chlorides, bromides, iodides, phenyl selenides, isonitriles and
thionocarbonates by several other silyl substituted silicon hydrides have
emerged.
By replacing one alkyl group by a R3Si group in trialkylsilanes the effect on
the hydrogen donating ability of SiH moiety increases by about one order of
magnitude, the effect being cumulative (see Chapter 3). Reductions of a variety
of organic derivatives were carried out by using RSi(H)Me2, where R ¼ SiMe3,
SiMe2SiMe3, or Si(SiMe3) 3, and the initiation given by benzoyl peroxide or tertbutyl
perbenzoate (AIBN was found not to be efficient in these cases) [106]. An
example for the simplest silane is reported in Reaction (4.66). A few rate
constants for the halogen abstraction by Me3SiSi(:)Me2 radicals are also
known and are smaller than that of Et3Si: or higher than that of (TMS) 3Si:
(Table 4.6).
Cl Me3SiSi(H)Me2 PhC(O)OOBu-t
O 110 �C
O
83%
(4.66)