In summary, we have shown that alpha-silylthioethers such as DMPTCS can serve as efficient masked hydroxyl groups.
They can also be used as surrogates to the PhMe2Si group, when this latter cannot be used, in case of :
* Oxidation of a C-Si bond of an allylsilane.
* Oxidation of a C-Si bond directly attached to, or remote from a cyclopropane ring.
SCOPE AND LIMITATIONS
* DMPTCS is easy to prepare on a large scale,
* It is easy to handle as a silane, chlorosilane, vinyl or allylsilane,
* It is stable to strong bases (LICKOR), acids (H2SO4 10%), electrophiles and Lewis acids,
* Other silicon groups such as PhMe2Si are left unchanged during oxidation, which allow for a possible sequential oxidation of differentiated silicon groups,
* The sulfone route allows the oxidation to be carried out in the presence of unprotected alcohol functions,
* beta-hydroxysilanes can be transformed into the corresponding diols in good yields, since no Peterson elimination usually takes place during the oxidation.
Parallely, our silicon group suffers from several disadvantages :
* The use of transition-metal catalysts (Rh, Pd, Cu) in the presence of DMPTCS is usually not compatible, the PhS group probably co-ordinating with the catalysts,
* Very few methods of introduction of DMPTCS are by now available,
* Although we did not check, it appears very unlikely that our method will be useful on subtrates having a thioether function !.
Extension of the scope of application of DMPTCS is now under way, with a particular emphasis on the mode of introduction of our silicon group. Application in the synthesis of more complex substrates will also be investigated.