Kinetic vs. thermodynamic control in hydrozirconation reactions

Abstract

Most synthetic applications of organo(chloro)zirconocenes involve the use of terminal zirconocenes derived from hydrozirconation of monosubstituted or symmetrical triple or double bonds. In our studies to effect stereoselective hydrozirconations of internal alkynes and alkenes, we have explored the alkoxy-directed hydrozirconation of homoallylic and bis-homoallylic alcohols. The discovery of a new method to prepare zirconocene hydrides in situ from readily available, air-stable zirconocene dihydride has allowed us to demonstrate for the first time that kinetic hydrozirconation products of internal, non-functionalized alkenes can be formed in preference over isomerized, thermodynamic products.