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.