Reactions of Lithium Silenolates with Acetylenes. Formation and Characterization of 2-Siladienes

Treatment of lithium silenolates, (Me 3 Si) 2 Si C(OLi)R 1 ( 1; R 1 = t-Bu, Ad, Mes), with phenyl-substituted acetylenes, PhC⋮CR 2 (R 2 = Ph, Me), produced lithium ethenylsilenolates, Ph(Me 3 Si)C CR 2 (Me 3 Si)Si C(OLi)R 1, cleanly. The ethenylsilenolates thus produced reacted readily with H 2 O and MeI to give Si-substitution products in good yield. In contrast, they underwent O-silylation with Et 3 SiCl to give 2-siladiene derivatives which were characterized by their NMR spectra.