The thermal conversion of sulfoxide 1 into the O-silylated cyclic O,S-aceta
l (2) is the first example of the sila-Pummerer rearrangement of cyclic org
anosilicon sulfoxides leading to ring expansion. The kinetics of the rearra
ngement are studied and thermodynamic parameters are determined. The result
s are in compliance with mechanism involving a pentacoordinated silicon ato
m. (C) 1998 Elsevier Science Ltd. All rights reserved.