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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The article was received on 19 Aug and first published on 04 Nov 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. This makes possible a far milder reaction process, including reactions with base-sensitive aldehydes. A chelate will form with small counterions Li and in apolar solvents, leading to a closed transition state. All four steps can be carried out in a single reaction vessel, and use of R 3 X is optional.

Julia Olefination

However, purification of the sulfone intermediate 2 leads to higher yield and purity. It is thought that the radical intermediates are able to equilibrate so that the more thermodynamically stable trans-olefin is produced most often.

Previous Article Next Article. Search articles by author Paul R. For reproduction of material from PPS: Back to tab navigation Download options Please wait 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.

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Views Read Edit View history. The E -selectivity is generally good to very good for alkenes with a low degree of olefinatiin, while the selectivity improves as a function of increased branching in olefinwtion substitutents. The alkoxide is functionalized with R 3 -X to give the stable intermediate 4. Unlike the phenyl sulfones, this alkoxide intermediate 2 is more reactive and will undergo a Smiles rearrangement [15] to give the sulfinate salt 4. It is believed that the compound also has anti-diabetic properties, but so far very little has been studied on this issue.

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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. The Julia-Kociensky Olefination is an alternative procedure, which leads to the olefin in one step. In the reductive variant, the adduct is usually acylated and then treated with a reducing agent, such as sodium amalgam [6] [7] or SmI 2.

Modified Julia Olefination, Julia-Kocienski Olefination

Back to tab navigation. If you are the author of this article you do not need to formally request permission to reproduce figures, diagrams etc. In the Julia—Kocienski olefination [16] the alkylating agent is a tetrazole. Protonation of the vinylic radical gives the desired product 6. Even though the carbanion is not configurationally or conformationally stable, it will prefer an arrangement with the R-groups further apart that will later lead to the E -alkene:. Site Search any all words.

In addition, there are fewer problems with scale-up than with the classical variant.

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By using this site, you agree to the Terms of Use and Privacy Policy. The reason for this is the sterically demanding phenyl group, which favors the following transition state:.

Compared to the WittigWittig-Horner, Perkinor transition-metal-catalyzed reactions juliia synthesize pterostilebene, the Julia olefination offers a simple, economical alternative method for preparation of pterostilbene. The Modified Julia Olefination enables the preparation of alkenes from benzothiazolyl sulfones and aldehydes in a single step:.

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. You do not have JavaScript enabled. Whether the anti or syn intermediate is generated can be influenced to some extent by the choice of reaction conditions:. Site Search any all words Main Categories.

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The Julia-Kocienski Olefination, a further refinement of the Modified Julia olefination, offers very good E -selectivity. In the initial versions of the reactions, the elimination was done under reductive conditions.

The phenyl sulfone anion 2 reacts with an aldehyde to form the alkoxide oelfination. This reaction juulia named after Philip J.

For reproduction of material juila all other RSC journals and books: For reproduction of material from PCCP: Jump to main content. Retrieved from ” https: It belongs to the group of phytoalexins, agents produced by plants to fight infections.

The Julia-Kocienski olefination serves as a powerful reaction in the synthesis of resveratrol analogues with 3,5-bis trifluoromethyl phenyl sulfones. The modified Julia olefination, also jula as the one-pot Julia olefination is a modification of the classical Julia olefination. Resveratrol is a biologically important stilbenoid which has been suggested to have many health benefits. 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.

The sulfinate salt 4 will spontaneously eliminate sulfur dioxide and lithium benzothiazolone 5 producing the desired alkene 6. Site Search any all words Main Categories. Most often R 3 is acetyl or benzoylwith acetic anhydride or benzoyl chloride used in the preparation of 2.