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