Diversity-oriented synthesis of multisubstituted olefins through the sequential integration of palladium-catalyzed cross-coupling reactions. 2-Pyridyldimethyl(vinyl)silane as a versatile platform for olefin synthesis

A novel strategy for the diversity-oriented synthesis of multisubstituted olefins, where 2-pyridyldimethyl (vinyl)silane functions as a versatile platform for olefin synthesis, is described. The palladium-catalyzed Heck-type coupling of 2-pyridyldimethyl(vinyl)silanes with organic iodides took place in the presence of Pd₂-(dba) ₃/tri-2-furylphosphine catalyst to give β-substituted vinylsilanes in excellent yields. The Heck-type coupling occurred even with α- and β-substituted 2-pyridyldimethyl(vinyl)silanes. The one-pot double Heck coupling of 2-pyridyldimethyl(vinyl)silane took place with two different aryl iodides to afford β,β-diarylated vinylsilanes in good yields. The palladium-catalyzed Hiyama-type coupling of 2-pyridyldimethyl(vinyl)silane with organic halides took place in the presence of tetrabutylammonium fluoride to give di- and trisubstituted olefins in high yields. The sequential integration of Heck-type (or double Heck) coupling and Hiyama-type coupling produced the multisubstituted olefins in regioselective, stereoselective, and diversity-oriented fashions. Especially, the one-pot sequential Heck/Hiyama coupling reaction provides an extremely facile entry into a diverse range of stereodefined multisubstituted olefins. Mechanistic considerations of both Heck-type and Hiyama-type coupling reactions are also described.