## Enantioselective Diene Cyclozirconation

Our objective is to use cyclozirconation to transform diene **40** into diol **44** in high enantiomeric purity. To this end, we have set out to computationally design a chiral bis Cp zirconium complex **41** such that one diastereomeric zirconacycle, **42** , would be substantially more stable than the other diastereomer, **43**.

Two considerations guided our design. The first was that the complex must be usefully chiral. We predict computationally, for instance, that the Brintzinger complex **39** would show no thermodynamic selectivity in the cyclozirconation of **40** .

The second consideration was that the zirconocene must be quite open. The Brintzinger complex (**39** ) participates only very slugglishly in intramolecular diene cyclozirconation. We thought that a good beginning place would be an ethano-bridged bis Cp such as **41** .

The question then was, how to make the ethano-bridged bis Cp usefully chiral? The key to this problem was to design substituents on the ethano bridge that would impart a sufficient chiral
twist to the Cp rings. After some exploration, we have found that 1,2-bis-1-naphthyl substituents (e.g. **41** ) are predicted computationally to work well (calculated stability difference between the two trans diastereomers for R = H is 2.0 kcal/mol, for R = CH3 is 2.4 kcal/mol; in both series the cis-fused diastereomers are less stable than either of the trans diastereomers).

# Douglass F. Taber . . . U. of Delaware

**For an overview, see:** computational catalyst design.
**Home Page: **Taber home page.

**Questions and comments to: **
*Douglass F. Taber*