Treatment of acetylenic compounds with PhMe 2 SiBEt 3 Li in the presence of a transition-metal catalyst affords vinylsilanes in good yields. Coexistence of methanoi as a proton source is essential for the completion of the reaction. ... The reversible nature of the reaction of PhMe 2 SiBEt 3 Li with acetylenic compounds has been clearly demonstrated by the following result. Treatment of the reaction mixture derived from 4-benzyloxy-1-butyne and PhMe 2 SiBEt 3 Li with ...