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

The chiral ligand precursor systems [l-C pM -R '-2-R 2-2-Cp2]ethane 5 a -d bearing two dif­ ferent cyclopentadienyl fragments (C p1, Cp2 = Cp, Ind, Flu) and a variable bridge substitu­ tion pattern (R 1, R2 = H, Ph, cyclopentyl, cyclohexyl) were prepared starting from the corre­ sponding epoxides. The solid state structures o f six organic intermediates are reported in order to prove the stereochemistry o f the ligand forming reactions. Treatment o f the dilithio salts o f 5a~d with ZrCl4 in CH2C12 afforded chiral a«sa-zirconocene dichlorides (6a-d).