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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Modified Julia Olefination, Julia-Kocienski Olefination
The following schematic displays the general scheme for synthesizing resveratrol analogues, where R 2 is an aryl group. A first possible mechanism proceeds through a planar radical that can rotate freely about the C-C bond. The replacement of the phenyl sulfones with heteroaryl sulfones greatly alters the reaction pathway.
Resveratrol is a biologically important stilbenoid which has been suggested to have many health benefits. Morley, Synlett, 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. Site Search any all words Main Categories. Kocienski for his modification to the Julia olefination.
This makes possible a far milder reaction process, including reactions with base-sensitive aldehydes. It proceeds with the same mechanism as the benzothiazole sulfone above. This transformation highly favors formation of the E -alkene.
Other hetero cyclic substituents can assume these roles, and offer somewhat different selectivity:. Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the Julia-Lythgoe olefination. Jump to site search. The Julia or modified Julia olefination reaction is a powerful and versatile synthetic transformation, widely utilized in the construction of complex julka products with excellent control of geometrical isomerism.
In contrast to the classical Julia Olefination, the Modified Julia Olefination offers the possibility of saving one or two synthesis steps. The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination.
The modified Julia olefination: The benzothiazolyl group BT can play olefinatiln roles: This page was last edited on 16 Augustat In the reductive variant, the adduct is usually acylated and then treated with a reducing agent, such as sodium amalgam   or SmI 2. The Julia olefination also known as the Julia—Lythgoe olefination is the chemical julla used in organic chemistry of phenyl sulfones 1 with aldehydes or ketones to give alkenes olefins 3 after alcohol functionalization and reductive elimination using sodium amalgam   or SmI 2.
Previous Article Next Article. If the material has been adapted instead of reproduced from the original RSC publication “Reproduced from” can be substituted with “Adapted from”. Keck demonstrated in that when the sodium amalgam reaction is run in MeOD as solvent, deuterium is incorporated into the product, olefinatjon contrast to the absence of incorporation seen in the SmI 2 reduction. The reductive elimination with sodium amalgam to furnish the alkene takes place in a second step.
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Goekjian, Synlett, 17 Marc Julia Philip Joseph Kocienski. For reproduction of material from all other RSC journals and books: Olefinatuon Search any all words Main Categories.
This may take some time to load. The intermediates that form react further to give E – and Z -isomers of the alkene:.