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The following scheme shows the epoxidation of cyclohexene with mCPBA. The epoxidation mechanism is concerted: the cis or trans geometry of the alkene starting material is retained in the epoxide ring of the product. The transition state of the Prilezhaev reaction is given below: [5]
Through a concerted mechanism, one of the substituents on the ketone group migrates to the oxygen of the peroxide group while a carboxylic acid leaves. [1] This migration step is thought to be the rate determining step. [2] [3] Finally, deprotonation of the oxocarbenium ion produces the ester. [1] Reaction mechanism of the Baeyer-Villiger ...
The reaction proceeds through what is commonly known as the "butterfly mechanism", first proposed by Bartlett, wherein the peracid is intramolecularly hydrogen-bonded at the transition state. [5] Although there are frontier orbital interactions in both directions, the peracid is generally viewed as the electrophile and the alkene as the ...
The epoxidation of allylic alcohols is a class of epoxidation reactions in organic chemistry. One implementation of this reaction is the Sharpless epoxidation. Early work showed that allylic alcohols give facial selectivity when using meta-chloroperoxybenzoic acid (m-CPBA) as an oxidant.
The mechanism of epoxidation with dioxiranes likely involves concerted oxygen transfer through a spiro transition state. As oxygen transfer occurs, the plane of the oxirane is perpendicular to and bisects the plane of the alkene pi system. The configuration of the alkene is maintained in the product, ruling out long-lived radical intermediates.
The reaction mechanism of the Sharpless dihydroxylation begins with the formation of the osmium tetroxide – ligand complex (2). A [3+2]-cycloaddition with the alkene (3) gives the cyclic intermediate 4. [9] [10] Basic hydrolysis liberates the diol (5) and the reduced osmate (6).
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A second significant side reaction in reactions of ketones and aldehydes is selanylation of the intermediate selenoxide. This process leads to elimination products retaining a carbon-selenium bond, [16] and is more difficult to prevent than the seleno-Pummerer reaction. Tertiary selenoxides, which are unable to undergo enolization, do not react ...