PerspectiveChemistry

Lending Handedness to the Cyclopentadienyl Ligand

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Science  26 Oct 2012:
Vol. 338, Issue 6106, pp. 479-480
DOI: 10.1126/science.1229830

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Summary

Chirality (handedness) represents an intrinsic property of many objects (such as hands and some molecules). The increasing demand for just one isomer of a compound, especially for pharmaceuticals, has been met largely by purifying racemic mixtures of chiral compounds. A powerful alternative to separation is to use chiral catalysts (1) to generate only the desired enantiomer; chiral metal complexes bearing specialized ligands based on heteroatoms such as phosphines and N-heterocyclic carbenes have been commonly used. In contrast, on pages 504 and 500 of this issue (2, 3), the authors achieved highly asymmetric C-H functionalizations (4) (see the figure, panel A) by introducing chiral features to one of the most common ligands used in organometallic chemistry, cyclopentadienyl (Cp). Ye and Cramer (2) report a chemical route to create a chiral Cp derivative, and Hyster et al. (3) describe a biochemical approach that uses a modified Cp in a chiral protein environment.