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

Other Silicon Hydrides 71
The reduction of thiocarbonyl derivatives by Et3SiH can be described as a
chain process under ‘forced’ conditions (Reaction 4.50) [89,90]. Indeed, in
Reaction (4.51) for example, the reduction of phenyl thiocarbonate in Et3SiD
as the solvent needed 1 equiv of dibenzoyl peroxide as initiator at 110 8C, and
afforded the desired product in 91 % yield, where the deuterium incorporation
was only 48 % [90]. Nevertheless, there are some interesting applications for
these less reactive silanes in radical chain reactions. For example, this method
was used as an efficient deoxygenation step (Reaction 4.52) in the synthesis of
4,4-difluoroglutamine [91]. 1,2-Diols can also be transformed into olefins using
the Barton–McCombie methodology. Reaction (4.53) shows the olefination
procedure of a bis-xanthate using Et3SiH [89].
O
O
PhOC(S)O
S
S
O
N
N
O
O
H
SMe
O
O
O O
N F F
Boc
RO
MeS
O
S
O
A
O O SMe
S
Et 3SiH (solvent)
[PhC(O)O] 2 (1 equiv)
110 �C, 3h
Et 3 SiD (solvent)
[PhC(O)O] 2 (1 equiv)
110 �C, 3h
Et 3 SiH (solvent)
[PhC(O)O] 2 (1 equiv)
110 �C, 1.5h
Et 3SiH (solvent)
(D)H
[PhC(O)O] 2 (0.6 equiv)
110 �C, 1.5h
O
O
H
O
96%
O
O
91%, H/D = 52/48
O
O O
N F F
Boc
99%
RO A
O
99%
(4.50)
(4.51)
(4.52)
(4.53)
A large body of absolute kinetic data, obtained by laser flash photolysis
techniques, for the reactions of Et3Si: radicals with organic halides is available