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 addition of a phenylsulfonyl carbanion to an aldehyde or ketone leads to an intermediate alcohol, which is esterified in situ. 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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A disadvantage of the Julia Olefination is its low tolerance for reducible functional groups. Retrieved from ” https: Back to tab navigation. Fetching data from CrossRef. Back to tab navigation Fetching data from CrossRef. Most often R 3 is acetyl or benzoylwith acetic anhydride or benzoyl chloride used in the preparation of 2.
Kocienski for his modification to the Julia olefination. The Julia-Kociensky Olefination is an alternative procedure, which leads to the olefin in one step. 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 uulia.
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 permission using Copyright Clearance Center. Back to tab navigation Download options Please wait All four steps can be carried out in a single reaction vessel, and use of R 3 X is optional.
A chelate will form with small counterions Li and juliia apolar solvents, leading to a closed transition state. The alkoxide is functionalized with R 3 -X to give the stable intermediate 4. In the reductive variant, the adduct is usually acylated and then treated with a reducing agent, such as sodium amalgam   or SmI 2. Site Search any all words Main Categories.
Modified Julia Olefination, Julia-Kocienski Olefination
The modified Julia olefination: Since the benzothiazole variation of the Julia olefination does not involve equilibrating intermediates, the stereochemical outcome is a result of the ju,ia of the initial carbonyl addition.
The reason for this is the sterically demanding phenyl group, which favors the following transition state:. Views Read Edit View history. Site Search any all words Main Categories.
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The article was received on 19 Aug and first published on 04 Nov Previous Article Next Article. The reductive elimination with sodium amalgam to furnish the alkene takes place in a second step.
Coupling reactions Olefination reactions Carbon-carbon bond forming reactions Addition reactions Free radical reactions Name reactions. Reproduced material should olefinatioh attributed as follows: Morley, Synlett, For reproduction of material from PCCP: The phenyl sulfone anion 2 reacts with an aldehyde to form the alkoxide 3.
Unlike the phenyl sulfones, this alkoxide intermediate 2 is more reactive and will undergo a Smiles rearrangement  to give the sulfinate salt 4. The Julia-Kocienski olefination serves as a powerful reaction in the synthesis of resveratrol analogues with 3,5-bis trifluoromethyl phenyl sulfones. However, purification of the sulfone intermediate 2 leads to higher yield and purity.
The intermediates that form react further to give E – and Z -isomers of the alkene:. 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.
The stereochemistry of the alkene 6 is independent of the okefination of the sulfone intermediate 4. The replacement of the phenyl sulfones with heteroaryl sulfones greatly alters the reaction pathway. The modified Julia olefination, also known as the one-pot Julia olefination is a modification of the classical Julia olefination.
From Wikipedia, the free encyclopedia. Pterostilbene is a stilbenoid chemically related to resveratrol.