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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If you are the author of this article you do not need to formally request permission to reproduce figures, diagrams etc. The Julia-Kocienski olefination serves as a powerful reaction in the synthesis juliz resveratrol analogues with 3,5-bis trifluoromethyl phenyl sulfones.
Back to tab navigation Download options Please wait The exact mechanism of the sodium amalgam reduction is unknown but has been shown to proceed through a vinylic radical species 5 . All four steps can be olefibation out in a single reaction vessel, and use of R 3 X is optional. The alkoxide is functionalized with R 3 -X to give the stable intermediate 4. The benzothiazolyl group BT can play several roles: A mechanistically related nucleophilic addition of the sulfonyl carbanion to a second equivalent of the BT sulfone leads to a side product.
Search articles by author Paul R. The Julia 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.
If the material has been adapted instead of reproduced from the original RSC publication “Reproduced from” can be substituted with “Adapted from”. Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the Julia-Lythgoe olefination.
Back to tab navigation Fetching data from Iulia. Modified Julia Olefination on Anhydrides: The modified Julia olefination: Retrieved from ” https: Even though the carbanion is not configurationally or conformationally stable, it will llefination an arrangement with the Olefiantion further apart that will later lead to the E -alkene:.
If you jullia not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center.
This page was last edited on 16 Augustat Marc Julia Philip Joseph Kocienski. The 1-phenyl-1 H -tetrazolyl sulfones do not have a tendency to self-condense, so they can first be deprotonated with base and then reacted with the aldehyde. The intermediates that form react olefinwtion to give E – and Z -isomers of the alkene:.
Modified Julia Olefination, Julia-Kocienski Olefination
It is thought that the radical intermediates are able to equilibrate so that the more thermodynamically stable trans-olefin is produced most often. The replacement of the phenyl sulfones with heteroaryl sulfones greatly alters the reaction pathway.
The phenyl sulfone jula 2 reacts with an aldehyde to form the alkoxide 3. Jump to main content. A chelate will form with small counterions Li and in apolar solvents, leading to a closed transition state.
The initial steps are straightforward. The reductive elimination with sodium amalgam to furnish the alkene takes olefinafion in a second step.
Resveratrol is a biologically important stilbenoid which has been suggested to have many health benefits.
The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination. Back to tab navigation. From Wikipedia, the free encyclopedia.
In the reductive variant, the adduct is usually acylated and then treated with a reducing agent, such olefiation sodium amalgam   or SmI 2. Compared to the WittigWittig-Horner, Perkinor transition-metal-catalyzed reactions to synthesize pterostilebene, the Julia olefination offers a simple, economical alternative method for preparation of pterostilbene. Morley, Synlett, If you are the author of this article you still need to obtain permission to reproduce the whole article in a third party publication with the exception of reproduction of the whole article oleffination a thesis or dissertation.
For reproduction of material from NJC: Other hetero cyclic substituents can assume these roles, and offer somewhat different selectivity:. Fetching data from CrossRef. Keck demonstrated in that when the sodium amalgam reaction is run in MeOD as solvent, deuterium is incorporated into the product, in contrast to the absence of incorporation seen in the SmI 2 reduction. Views Read Edit View history. Site Search any all words Main Categories.