Influence of the Silyl Group on the Reactivity of Some Ortho-Lithiated Aryl Alkyl Sulfides

The
lithiation of brominated aryl (α-dimethylsilyl)­alkyl sulfides
in diethyl ether produces stable heterocyclic silanes, which were
characterized by 1H, 13C, and 29Si
NMR spectroscopy and by X-ray crystallography. The reaction involves
the intramolecular attack of the phenyl carbanion on the silicon atom
with the formation of a pentacoordinated silicon intermediate. The
stability of the formed intermediate depends on the solvent. It decomposes
easily in THF at −78 °C with Si–C bond cleavage;
however, it is stable in diethyl ether at room temperature. Addition
of water results in the Si–H bond cleavage, while the heterocyclic
ring containing the silicon atom is conserved.