Asymmetric epoxidation is a subset of asymmetric catalytic oxidations. Epoxidations convert prochiral (and other)

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

s to chiral epoxide derivatives. In asymmetric epoxidation, the two chiral products are produced in unequal amounts. The same catalysts are useful in the diastereoselective epoxidations, whereby one chiral alkene epoxidizes more rapidly than its enantiomer. Two popular versions of asymmetric epoxidations are: *

Sharpless epoxidation The Sharpless epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols. The oxidizing agent is ''tert''-butyl hydroperoxide. The method relies on a catalyst formed f ...

, which uses titanium-based catalyst and tartrate esters as the chiral ligand. This methodology is one of the premier

enantioselective In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non- stereospecific creation of a new stereocenter or during a non-stereospecific transformation o ...

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

s. It is used to prepare 2,3-epoxyalcohols from primary and secondary

allylic alcohol Allyl alcohol (IUPAC name: prop-2-en-1-ol) is an organic compound with the structural formula . Like many Alcohol (chemistry), alcohols, it is a water-soluble, colourless liquid. It is more toxic than typical small alcohols. Allyl alcohol is us ...

s.Hill, J. G.; Sharpless, K. B.; Exon, C. M.; Regenye, R. '' Org. Synth.'', Coll. Vol. 7, p. 461 (1990); Vol. 63, p. 66 (1985).
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) Sharpless epoxidation DE

Jacobsen epoxidation The Jacobsen epoxidation, sometimes also referred to as Jacobsen-Katsuki epoxidation is a chemical reaction which allows enantioselective epoxidation of unfunctionalized alkyl- and aryl- substituted alkenes. It is complementary to the Sharpless ...

, which uses a manganese-based catalyst supported by a chiral

salen ligand Salen refers to a tetradentate C2-Symmetric ligands, C2-symmetric ligand synthesized from salicylaldehyde (sal) and ethylenediamine (en). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, prim ...

. *

Shi epoxidation The Shi epoxidation is a chemical reaction described as the asymmetric epoxidation of alkenes with oxone (potassium peroxymonosulfate) and a fructose-derived catalyst (1). This reaction is thought to proceed via a dioxirane intermediate, generate ...

, which uses a chiral

organocatalyst In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an Organic compound, organic catalyst. This "organocatalyst" consists of carbon, hydrogen, sulfur and other nonmetal elements fo ...

and

potassium peroxymonosulfate Potassium peroxymonosulfate is widely used as an oxidizing agent, for example, in pools and spas (usually referred to as monopersulfate or "MPS"). It is the potassium salt (chemistry), salt of peroxymonosulfuric acid. Potassium peroxymonosulfate ...

as the O atom source

References

{{Reflist Epoxidation reactions Organic redox reactions Epoxides Catalysis