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

106 Addition to Unsaturated Bonds
and a-dicarbonyl compounds, respectively. The proposed reaction mechanism
is summarized in Scheme 5.9 and involves the addition of Me3Si: radical to the
carbonyl group and subsequent hydrogen abstraction from Bu3SnH. In turn,
the Bu3Sn: radical displaced the Me3Si: radical from PhSeSiMe3 and completes
the radical reaction cycle (see Section 1.1).
X CHO
PhSeSiMe 3
Bu 3SnH
AIBN, 80 �C
X CH 2 OSiMe 3
X = H, Me, OMe, Cl 74 - 85%
Ph
O
O
R
R = Me
R = Ph
PhSeSiMe 3
Bu 3SnH
AIBN, 80 �C
Me 3 Si
Me3Si O
Bu3SnH O
R X
R X Me3Si O
Me 3Si
PhSeSnBu 3
Bu 3Sn
PhSeSiMe 3
Ph
O
O
52%
73%
R X
R
(5.29)
(5.30)
Scheme 5.9 Propagation steps for hydrosilylation of carbonyl compounds using
PhSeSiMe3=Bu3SnH system
5.3.3 RADICAL BROOK REARRANGEMENT
The 1,2 migration of the silyl group in Reaction (5.31) somehow recalls the
addition of silyl radicals to carbonyl moieties. The initial a-silyl alkoxyl radical
47 could be formally one of the two possible adducts of silyl radical to the
carbonyl group, although evidence has never been found for such a reaction.
On the other hand, the rearranged carbon-centred radical 48 is identical to the
adduct of silyl radical with the carbonyl group. In this section, we briefly
describe this rearrangement, which is also called radical Brook rearrangement
because it resembles the well known analogous ionic reaction [61].