Zirconocene-Mediated Highly Regio- and Stereoselective Synthesis of Multisubstituted Olefins Starting from 1-Alkynylboronates

Multisubstituted olefins are efficiently prepared by the zirconocene-mediated regio- and stereoselective coupling between 1-alkynylboronates and ethylene, followed by sequential transformation in moderate to high yields. The proper combination of substrates and reaction conditions is important for high yields. The synthesis of various tetrasubstituted alkenes in a regio- and stereocontrolled manner is described. This methodology has been applied to the synthesis of (Z)-tamoxifen in a concise, regio- and stereoselective manner. This multicomponent coupling strategy involves the characteristics of 1-alkynylboronates toward high selectivities followed by palladium(0)-mediated cross-coupling with aryl halides.