alpha-Silylthioethers as masked hydroxyl groups

PROBLEM : Design of a silicon group which would possess the advantages of the silicon groups cited above, specifically :
- a good stability to a wide range of reaction conditions,
- but, also an acceptable lability for an easy oxidation.

- Utilisation of an alpha-silylthioether function such as in 1.

- alpha-silylthioethers should be compatible with many reaction conditions,
- they should be easily converted into the oxidizable siloxane 3, using a sila-Pummerer rearrangement (Scheme 1) [6],
- The real masked hydroxyl group (i.e. 3) is revealed only in the last stage of the sequence.

The dimethyl(1-phenylthio)cyclopropylsilyl group (DMPTCS) (as in 1) is easily available [7] and undergoes clean and fast sila-Pummerer rearrangement, producing the required siloxane (e.g. 3) in almost quantitative yield [8].