JULIA OLEFINATION PDF

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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Views Read Edit View history. In the initial versions of the reactions, the elimination was done under reductive conditions. By using this site, you agree to the Terms of Use and Privacy Policy. Application to the Synthesis of Maculalactone B N.

Jump to site search. The Julia olefination also known as the Julia—Lythgoe olefination is the chemical reaction 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 [1] [2] or SmI 2.

Previous Article Next Article. This page was last edited olefibation 16 Augustat The article was received on 19 Aug and first published on 04 Nov 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.

Morley, Synlett, The utility of this connective olefination reaction arises from its versatility, its wide functional group tolerance, and the mild reaction conditions under which the reaction proceeds. The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination.

All four steps can be carried out in a single olefinatoin vessel, and use of R 3 X is optional. The exact mechanism of the sodium amalgam reduction is unknown but has been shown to proceed through a vinylic radical species 5 [11].

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Julia-Lythgoe Olefination

The Julia-Kocienski olefination serves as a powerful reaction in the synthesis of resveratrol analogues with 3,5-bis trifluoromethyl phenyl sulfones. The phenyl sulfone anion 2 reacts with an aldehyde to form the alkoxide 3. The replacement of the phenyl sulfones with heteroaryl olefinatino greatly alters the reaction pathway. It proceeds with the same mechanism as the benzothiazole sulfone above. The reason for this is the sterically demanding phenyl group, which favors the following transition state:.

Unlike the phenyl sulfones, this alkoxide intermediate 2 is more reactive and will undergo a Smiles rearrangement [15] to give the sulfinate salt 4. Retrieved from ” https: This transformation highly favors formation of the E -alkene. Marc Julia Philip Joseph Kocienski.

If you are 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 juliia using Olefihation Clearance Center. The Julia-Kociensky Olefination is an alternative procedure, which leads to the olefin in one step. Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the Julia-Lythgoe olefination.

Site Search any all words. 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 Olefinagion -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. However, purification of the sulfone intermediate 2 leads to higher yield and purity. In contrast to the classical Julia Olefination, the Modified Julia Olefination offers the possibility of saving one or two synthesis olefinztion.

This makes possible a far milder reaction process, including reactions with base-sensitive aldehydes. The addition of a phenylsulfonyl carbanion to an aldehyde or ketone leads to an intermediate alcohol, which is esterified in situ. Sulfoxides in Julia-Lythgoe Olefination: Go to our Instructions for using Copyright Clearance Center page for details. You do not have JavaScript enabled. This may take some time to load. Modified Julia Olefination on Anhydrides: Resveratrol is a biologically important stilbenoid which has been suggested to have many health benefits.

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The sulfinate salt olefonation will spontaneously eliminate sulfur dioxide and lithium benzothiazolone 5 producing the desired alkene 6.

Other hetero cyclic substituents can assume these roles, and offer somewhat different selectivity:. Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Back to tab navigation Fetching data from CrossRef. It is thought that the radical intermediates are able to oleefination so that the more thermodynamically stable trans-olefin is produced most often.

Julia-Lythgoe Olefination | Chem-Station Int. Ed.

For reproduction of material from all other RSC journals and books: A chelate will form with small counterions Li iulia in apolar solvents, leading to a closed transition state. In addition, there are juliw problems with scale-up than with the classical variant. The Julia-Kocienski Olefination, a further refinement of the Modified Julia olefination, offers very good E -selectivity.

The following table shows the selectivity and yields for BT and PT sulfones in various solvents, where they are first metalated with various bases and then reacted with an aldehyde. 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 in a thesis or dissertation. The reductive elimination with sodium amalgam to furnish the alkene julla place in a second step.