Generation of a silylethylene-titanium alkoxide complex. A versatile reagent for silylethylation and silylethylidenation of unsaturated compounds

(Trimethylsilyl)ethylene-titanium alkoxide complex (1) was generated from trimethyl(vinyl)silane, Ti(O-i-Pr)(4), and i-PrMgCl as a preformed alkene-titanium complex and reacted with several unsaturated compounds such as aldehyde, imine, other vinylsilane, and acetylene to give the corresponding coupling products 4a-f, 6, 8, and 10a-d in a regioselective manner. Both of the two carbon-titanium bonds of the complex 1 reacted successively with esters to afford silylcyclopropanols 11a-j, 13, and 15, some synthetic applications of which were illustrated in the preparation of beta-silyl ketones 16 and cyclopropenes 17. Asymmetric addition of 1 to a chiral acyloxazolidinone 19 gave optically active cyclopropanol (+)-11a of 50% ee.