Design of the alpha-silylthioether group

The Dimethyl(1-phenylthio)cyclopropylsilyl group was found to be the best candidate since the cyclopropyl ring is known to slow down the sila-Pummerer [8]. Heating (benzene or toluene, reflux) is then required to get the siloxane intermediate.

We tried other alpha-silylthioether groups which unfortunately did not allow us to control efficiently the sila-Pummerer rearrangement. For instance, the sulfoxide i underwent the sila-Pummerer rearrangement at room temperature giving a mixture of siloxane and unknown products. We also observed that alpha-silylsulfoxide having a t-BuS instead of a PhS group (as in ii) gave rise to a fast rearrangement producing complex mixtures.