Synthesis of Ethylene Bridged Biscyclopentadiene Ligand Precursor Compounds and Some of their ansa-Zirconocene Derivatives Chiral Epoxides: A Synthetic Strategy of High Variability

The chiral ligand precursor systems [1-Cp¹-1-R¹-2-R-²-2-Cp²]ethane 5a–d bearing two different cyclopentadienyl fragments (Cp¹, Cp² = Cp, Ind, Flu) and a variable bridge substitution pattern (R¹, R² = H, Ph, cyclopentyl, cyclohexyl) were prepared starting from the corresponding epoxides. The solid state structures of six organic intermediates are reported in order to prove the stereochemistry of the ligand forming reactions. Treatment of the dilithio salts of 5a–d with ZrCl₄ in CH₂Cl₂ afforded chiral ansa-zirconocene dichlorides (6a–d).