Diversity-oriented synthesis of multi substituted 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 o lefins, where 2-pyridyldimethyl(vinyl)silane functions as a versatile platf orm for olefin synthesis, is described. The palladium-catalyzed Heck-type c oupling of 2-pyridyldimethyl(vinyl)silanes with organic iodides took place in the presence of Pd-2(dba)(3)/tri-2-furylphosphine catalyst to give beta -substituted vinylsilanes in excellent yields. The Heck-type coupling occur red even with alpha- and beta -substituted 2-pyridyldimethyl(vinyl)silanes. The one-pot double Heck coupling of 2-pyridyldimethyl(vinyl)silane took pl ace with two different aryl iodides to afford beta,beta -diarylated vinylsi lanes in good yields. The palladium-catalyzed Hiyama-type coupling of 2-pyr idyidimethyl(vinyl)silane with organic halides took place in the presence o f tetrabutylammonium fluoride to give di- and trisubstituted olefins in hig h yields. The sequential integration of Heck-type (or double Heck) coupling and Hiyama-type coupling produced the multisubstituted olefins in regiosel ective, stereoselective, and diversity-oriented fashions. Especially, the o ne-pot sequential Heck/Hiyama coupling reaction provides an extremely facil e entry into a diverse range of stereodefined multisubstituted olefins. Mec hanistic considerations of both Heck-type and Hiyama-type coupling reaction s are also described.