A direct method to access various functional arylalkoxysilanes by Rh-catalysed intermolecular C-H silylation of alkoxysilanes.

Efficient protocols for intermolecular C-H silylations of unactivated arenes and heteroarenes with HMeSiOEt are disclosed. The silylations are catalysed by a Rh-complex (0.5 mol%) derived from commercially available [Rh(coe)Cl] and (,)-Ph-BPE in the presence of cyclohexene at 100 °C, furnishing desired arylethoxydimethylsilanes up to 99% yield. The regioselectivity is mainly affected by the steric bulk of the substituents in arenes and by electronic effects as an ancillary factor. Mechanistic study revealed that the mono-hydrido dimeric Rh-complex, [Rh(Ph-BPE)(μ-H)(μ-Cl)], is an active catalytic intermediate, which further suppresses the formation of redistribution byproducts in the silylation. Preliminary results show that the current protocol can be extended to double C-H silylations affording bis-silylated arenes and is applicable to the silylation of HMeSi(OEt) to deliver the corresponding (aryl)SiMe(OEt).