Allylsilanes

methyl group â to the trimethylsilyl group in 137. [213] This procedure is also applicable to
the preparation of cyclopentanoid allylsilanes containing an oxygen functionality on the
cyclopentane ring. [214]
Scheme 56 Cyclopentanoid Allylsilanes by an Intramolecular Ene Reaction [212,213]
R 3
R 3
Me3Si
R 2
136
R 1
CO2R 4
heat
R 3
R 3
H
H
CO 2R 4
H
R 2
137
R 1 R 2 R 3 R 4 Conditions Yield (%)
of 138
CH(R 1 )SiMe 3
R 3
R 3
R 2
H
H
138
bp (8C/Torr)
of 138 a
R 1
SiMe3
CO2R 4
H H H Et 2528C, 45 h 98 115±120/0.01 [212,213]
Me H H Me 2438C, 16 h 93 130±131/0.3 [212,213]
H H Me Et 2458C, 30 h 97 125±130/0.01 [212,213]
H Me H Me 2438C, 16 h 0 n.r. [212,213]
a n.r. = not reported.
FOR PERSONAL USE ONLY
880 Science of Synthesis 4.4 Silicon Compounds
Formation of (3-Cyclopentylallyl)silanes 138 by Thermolytic Cyclization of Dienes 136;
General Procedure: [213]
A Pyrex tube containing 5% diene 136 in drytoluene was purged with argon and sealed.
The tube was heated in a constant-temperature tubular furnace (temperatures and times
given in Scheme 56). After the mixture had cooled to rt, the solvent was removed in vacuo
and the residue was distilled to give allylsilane 138.
4.4.40.34 Method 34:
From Alkenyl Fischer Carbene Complexes by a [2+1]-Insertion Reaction
with Triorganosilanes
A [2+1]-insertion reaction of Fischer carbene complexes with triorganosilanes gives allylsilanes,
for example, 140, under mild conditions (Scheme 57). [215,216] The reaction is regioselective
at the metal±carbene bond and shows no significant hydrosilylation at the alkenyl
site. For more electron-rich â-methoxycarbene complexes, for example, 139
(R 1 = Ph; R 2 = OMe), the reaction is relativelysluggish, presumablydue to a decrease in
the electrophilicityof the carbene carbon. At present, this seems to offer the onlyavailable
route for straightforward preparation of 1-methoxyallylsilanes.
Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG
Ref