The stereoselectivity of the Julia olefination is determined by the radical intermediate. The intermediates, both the cis and trans, can equilibrate allowing the. O. H. R2. R1. R2. +. Base. Overview of the Julia-Kocienski Olefination. Evans’ Group Literature Seminar. Scott Peterson. Sept. 26, Title 9/25/03 PM. The Julia-Lythgoe olefination involves the nucleophilic addition of lithiosulfones to carbonyl compounds, acylation, and reductive treatment of.
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A first possible mechanism proceeds through a planar radical that can rotate freely about the C-C bond. The E -selectivity is generally good to very good for alkenes with a low degree of substitution, while the selectivity improves as a function of increased branching in the substitutents.
Authors contributing to RSC publications journal articles, books or book chapters do not need to formally request permission to reproduce material contained in this article provided that the correct acknowledgement is given with the reproduced material.
Resveratrol is a biologically important stilbenoid which has been suggested to have many health benefits. A mechanistically related nucleophilic addition of the sulfonyl carbanion to a second equivalent of the BT sulfone leads to a side product.
Since the benzothiazole variation of the Julia olefination does not involve equilibrating intermediates, the stereochemical outcome is a result of the stereochemistry of the initial carbonyl addition. Jump to main content. If you are the author of this article you still need to obtain permission to reproduce klefination whole article in a third party publication with the exception of reproduction of the whole article in a thesis or dissertation.
It proceeds with the same mechanism as the benzothiazole sulfone above.
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Back to tab navigation. All four steps can be carried out in a single reaction vessel, and use of R 3 X is optional. Reproduced material should be attributed as follows: The addition of a phenylsulfonyl carbanion to an aldehyde or ketone leads to an intermediate alcohol, which is esterified in situ.
The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination. Journal of the Chemical Society, Olefinnation Transactions 1.
Julia olefination – Wikipedia
The Julia-Kociensky Olefination is an alternative procedure, which leads to the olefin in one step. It belongs to the group of phytoalexins, agents produced by plants to fight infections. The Modified Julia Olefination enables the preparation of alkenes from benzothiazolyl sulfones and aldehydes in a single step:.
One adaptation of the Julia-Kocienski olefination gives the synthesis of the stilbenoid resveratrola natural compound found in common foods like grapes, wines and nuts. This transformation highly favors formation of the E -alkene.
It is believed that the compound also has anti-diabetic properties, but so far very little has been olefinatkon on this issue. The jklia Julia Olefination with sodium amalgam might possibly proceed via an initial elimination to an alkenyl sulfone, which would then undergo homolytic cleavage involving single electron transfer.
As a result, this reaction often generates a mixture of alkene stereoisomers. For reproduction of material from PCCP: This makes possible a far milder reaction process, including reactions with base-sensitive aldehydes. The Olefknation or modified Julia olefination reaction is a powerful and versatile synthetic transformation, widely utilized in the construction of complex natural products with excellent control of geometrical isomerism. In the Julia—Kocienski olefination  the alkylating agent is a tetrazole.
Since the cis – and trans -vinyl radicals can equilibrate at this stage and the trans -radical is the more stable of the two, both diastereomeric acetoxy sulfones would still lead selectively to the same product.
The initial steps are straightforward. The replacement olefinationn the phenyl sulfones with heteroaryl sulfones greatly alters the reaction pathway. The intermediates that form react further to give E – and Z -isomers of the alkene:.
For reproduction of material from all other RSC journals and books: Juliz Article Next Article. The reductive elimination with sodium amalgam to furnish the alkene takes place in a second step. Back to tab navigation Download options Please wait Application to the Synthesis of Maculalactone B N. If the material has been adapted instead of reproduced from the original RSC publication “Reproduced from” can be substituted with “Adapted from”.
However, purification of the sulfone intermediate 2 leads to higher yield and purity.