JULIA OLEFINATION PDF

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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 Julia olefination also known as julua 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. 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.

All four steps can be carried out in a single reaction vessel, and use of R 3 X is optional. However, purification of the sulfone intermediate 2 leads to higher yield and purity.

Most often R 3 is acetyl or benzoylwith acetic anhydride or benzoyl chloride ooefination in the preparation of 2.

Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the Julia-Lythgoe olefination. In the initial versions of the reactions, the elimination olefnation done under reductive conditions. More recently, a modified version that avoids this step was developed. The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination.

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. The initial steps are straightforward. The phenyl sulfone anion 2 reacts with an aldehyde to form the olefinatiion 3. The alkoxide is functionalized with R 3 -X to give the stable intermediate 4.

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The exact mechanism of the sodium amalgam reduction is unknown but has been shown to proceed through a vinylic radical species 5 [11]. Protonation of the vinylic radical gives the desired product 6. The stereochemistry of the alkene 6 is independent of the stereochemistry of the sulfone intermediate 4. It is thought that the radical intermediates are able to equilibrate so that the more thermodynamically stable trans-olefin is produced most often.

Julia olefination – Wikipedia

This transformation highly favors formation of the E -alkene. The modified Julia olefination, also known as the one-pot Julia olefination is a modification of the classical Julia olefination. The replacement of the phenyl sulfones with heteroaryl sulfones greatly alters the reaction pathway.

Unlike the phenyl sulfones, this alkoxide intermediate 2 is more reactive and will undergo a Smiles rearrangement [15] to give the sulfinate salt 4. The sulfinate salt 4 will spontaneously eliminate olefinztion dioxide and lithium benzothiazolone 5 producing the desired olevination 6.

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. As a result, this reaction often generates a mixture of alkene stereoisomers.

Julia olefination

The Julia-Kocienski Olefination, a further refinement of the Modified Julia olefination, offers very good E -selectivity.

In the Julia—Kocienski olefination [16] the alkylating agent is a tetrazole. It proceeds with the same mechanism as the benzothiazole sulfone above. The high E -selectivity of the Julia—Kocienski olefination is the result of kinetically controlled diastereoselective addition of metalated 1-phenyl-1H-tetrazolyl PT sulfones to nonconjugated aldehydes. This reaction is named after Philip J. Kocienski for his modification to the Julia olefination.

The Julia or modified Julia olefination reaction is a powerful and versatile synthetic transformation, widely utilized in the construction of complex natural products jukia excellent control of geometrical isomerism. Pterostilbene is a stilbenoid chemically related to resveratrol. It belongs to the group of phytoalexins, agents produced by plants to fight infections.

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It oletination believed that the compound also has anti-diabetic properties, but so far very little has been studied on this issue. 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.

Juliq adaptation of the Julia-Kocienski olefination gives olefinxtion synthesis of the stilbenoid resveratrola natural compound found in common foods like grapes, wines and nuts.

Modified Julia Olefination, Julia-Kocienski Olefination

Resveratrol is juliaa biologically important stilbenoid which has been suggested to have many health benefits. The Julia-Kocienski olefination serves as a powerful reaction in the synthesis of resveratrol analogues with 3,5-bis trifluoromethyl phenyl sulfones. The following schematic displays the general scheme for synthesizing resveratrol analogues, where R 2 is an aryl group.

The following schematic displays the Julia-Kocienski olefination used to achieve the precursor to the natural product, as indicated by use of the PT-sulfone. From Wikipedia, the free encyclopedia. Retrieved from ” https: Coupling reactions Olefination reactions Carbon-carbon julka forming reactions Addition reactions Free radical reactions Name reactions.

Julia-Lythgoe Olefination

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Marc Julia Philip Joseph Kocienski.