Regiospecific synthesis of alpha-lithiated alkoxysilanes

α-Lithioalkoxysilanes, [(RO)R2′Si]CH(Li)(R″) (R=Me, Et; R′=Me, Ph; R″=H, SiMe3), can be prepared by treating the appropriate alkoxysilane with tert-butyllithium in hydrocarbon solvents. For R=Me or Et, R′=Me, and R″=H or SiMe3, the α-lithioalkoxysilanes are produced in high yield. Similar treatment of alkoxysilane 12, EtOPh2SiCH3, afforded the corresponding α-lithioalkoxysilane 13 (R=Et, R′=Ph and R″=H), in moderate yield, along with substitution product 14, tert-BuPh2SiCH3. Analogous reactions with n-butyl- and sec-butyllithium in hydrocarbon solvent produced significant or exclusive substitution at silicon, rather than α-lithiation.