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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3a<br />
O<br />
OSiMe 3<br />
O<br />
OMe<br />
+ Me Me<br />
Cl 3TiO<br />
Me<br />
SPh<br />
7a<br />
SPh<br />
E<br />
TiCl4 _<br />
Me3SiCl O<br />
O<br />
Me<br />
OMe<br />
TiCl 4<br />
TiCl 4<br />
(2 equiv.)<br />
CH 2Cl 2<br />
_ 78 20 °C<br />
H 2O<br />
Scheme 7. Possible mechanism <strong>of</strong> the formation <strong>of</strong> 8a<br />
_<br />
23<br />
SPh<br />
O<br />
Me Me<br />
Cl<br />
Cl 3TiO<br />
Me<br />
8a (48%)<br />
F<br />
Me<br />
OMe<br />
_<br />
(Cl3Ti) 2O<br />
+<br />
TiCl3 SPh O<br />
OMe<br />
_<br />
Cl<br />
The cyclization <strong>of</strong> 1-trimethylsilyloxy-3-arylthio-1,3-butadienes 3a,d,f,g,i,k,o with 1,1-<br />
diacylcyclopropanes 7a-e, in the presence <strong>of</strong> TiCl4 or TiBr4, afforded the 5-haloethyl-<br />
2-(arylthio)benzoates 8a-x (Scheme 8, Table 3). Products 8b-d,g,i,j,l,o, derived from<br />
the unsymmetrical cyclopropanes 7b-d, were formed with very good regioselectivity.<br />
This can be explained by regioselective attack <strong>of</strong> the terminal carbon atom <strong>of</strong> diene 3<br />
onto the acetyl rather than the less reactive aroyl group <strong>of</strong> 7b-d.