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Asymmetric dihydroxylation adds two hydroxyl groups across an alkene while favouring one stereochemical product. In the Sharpless approach, a chiral ligand controls an osmium-based catalytic environment, turning an otherwise face-symmetric reaction into an enantioselective transformation.^[ref]

The new oxygen-bearing centres are formed in a correlated addition. Substrate geometry and the ligand's handedness jointly determine which stereoisomer is favoured.

An asymmetric oxidation is an oxidation that favours one stereochemical outcome, often by using a chiral catalyst. Asymmetric epoxidation and asymmetric dihydroxylation are examples: an oxygen-transfer process also creates controlled spatial structure.^[ref]

Oxidation state change and enantioselectivity describe different aspects of the result. A high chemical yield therefore does not by itself establish a high enantiomeric excess.

A chiral catalyst provides a handed reaction environment that can favour formation of one enantiomer. The competing substrate–catalyst arrangements are diastereomeric, so their activation free energies can differ.^[ref]

For two competing pathways obeying transition-state kinetics, $k_1/k_2\simeq \exp [-(\Delta G_1^{‡}-\Delta G_2^{‡})/(RT)]$. A modest free-energy difference can therefore produce a substantial product ratio. Reversible steps and product equilibration require additional analysis.