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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,

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