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Nucleophilic epoxidation is the formation of epoxides from electron-deficient double bonds through the action of nucleophilic oxidants. Nucleophilic epoxidation methods represent a viable alternative to electrophilic methods, many of which do not epoxidize electron-poor double bonds efficiently.
The Sharpless epoxidation is viable with a large range of primary and secondary alkenic alcohols. Furthermore, with the exception noted above, a given dialkyl tartrate will preferentially add to the same face independent of the substitution on the alkene.To demonstrate the synthetic utility of the Sharpless epoxidation, the Sharpless group created synthetic intermediates of various natural ...
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, generated from the catalyst ketone by oxone (potassium peroxymonosulfate).
The Juliá–Colonna epoxidation is an asymmetric poly-leucine catalyzed nucleophilic epoxidation of electron deficient olefins in a triphasic system.The reaction was reported by Sebastian Juliá at the Chemical Institute of Sarriá in 1980, [1] with further elaboration by both Juliá and Stefano Colonna (Istituto di Chimica Industriale dell'Università, Milan, Italy).
Asymmetric epoxidation is often feasible. [4] 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.
In the realm of asymmetric methods, both the Sharpless epoxidation [11] and Jacobsen epoxidation [12] surpass asymmetric dioxirane oxidations in enantioselectivity. Additionally, enzymatic epoxidations are more enantioselective than dioxirane-based methods; however, such methods often suffer from operational difficulties and low yields.
It is used as an asymmetric catalyst in the Jacobsen epoxidation, which is renowned for its ability to enantioselectively transform prochiral alkenes into epoxides. [ 1 ] [ 2 ] Before its development, catalysts for the asymmetric epoxidation of alkenes required the substrate to have a directing functional group, such as an alcohol as seen in ...
It is often referred to as asymmetric amplification, a term coined by Oguni and co-workers. [4] An example of a positive non-linear effect is observed in the case of Sharpless epoxidation with the substrate geraniol.In all cases of chemical reactivity exhibiting (+)-NLE, there is an innate tradeoff between overall reaction rate and ...