List of used abbreviations - RosDok - Universität Rostock
List of used abbreviations - RosDok - Universität Rostock
List of used abbreviations - RosDok - Universität Rostock
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+<br />
PhS<br />
Me<br />
Me<br />
3a<br />
Me3SiO O<br />
OSiMe 3<br />
4a<br />
Me3SiO O<br />
+<br />
PhS<br />
OSiMe 3<br />
Me<br />
A<br />
O<br />
O<br />
OMe<br />
Me<br />
TiCl 4<br />
_<br />
TiCl 4<br />
Me<br />
1a<br />
Me 3SiCl<br />
OMe<br />
TiCl 3<br />
Me<br />
TiCl 4<br />
CH 2Cl 2<br />
_ 78 to 20 °C<br />
14 h<br />
Me 3SiCl<br />
(Me 3Si) 2O<br />
16<br />
Me<br />
Me<br />
Me<br />
PhS<br />
SPh<br />
O<br />
5a (56%)<br />
SPh O<br />
B C<br />
Scheme 2. Possible mechanism <strong>of</strong> the formation <strong>of</strong> 5a<br />
HCl<br />
Me<br />
D<br />
O<br />
O<br />
Me<br />
H 2O<br />
Me<br />
OMe<br />
OMe<br />
OTiCl 3<br />
OMe<br />
TiCl 4<br />
The regioselective formation <strong>of</strong> 5h and 5k might be rationalized by comparison <strong>of</strong> the<br />
resonance structures <strong>of</strong> the cations formed by reaction <strong>of</strong> TiCl4 with 3-silyloxy-2-en-1-<br />
one 4f (Scheme 4). It can be expected that resonance structure A1 is more stable<br />
than A2, due to the σ-donating effect <strong>of</strong> the methyl group. The phenyl group is<br />
presumably twisted out <strong>of</strong> plane, due to steric reasons. The reactions may proceed,