Asymmetric catalytic oxidation

Reactions according to substrate

Hydrocarbons

Typically a prochiral C-H bond is converted to a chiral alcohol. Many examples of this important reaction result from the action of cytochrome P450, which allows these enzymes to process prodrugs and xenobiotics. Alpha-ketoglutarate-dependent hydroxylases also catalyze hydroxylations.

Alkenes

The oxidation of alkenes has attracted much attention. Asymmetric epoxidation is often feasible. One named reaction is the Jacobsen epoxidation, which uses manganese-salen complex as a chiral catalyst and NaOCl as the oxidant. The Sharpless epoxidation using chiral N-heterocyclic ligands and osmium tetroxide. Instead of asymmetric epoxidation, alkenes are susceptible to asymmetric dihydroxylation. The method is especially applicable to allyl alcohols using a catalyst derived from titanium isopropoxide and diethyl tartrate. tert-Butyl hydroperoxide is the oxidant. This conversion, the Sharpless asymmetric dihydroxylation, was recognized by a Nobel Prize. Metal-free asymmetric olefin oxidation have been developed. For example, the Shi epoxidation of alkenes using oxone can be made asymmetric using a fructose-derived catalyst.

Sulfur compounds

The enantioselective oxidation of unsymmetrical thioethers to sulfoxides is a well established. The common over the counter medication Esomeprazole (brandname: Nexium) involves such an asymmetric oxidation as its final step. Even disulfides are susceptible to oxidation to chiral thiosulfinites.