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Sharpless, Mechanism of Asymmetric Epoxidation.

Epoxide Opening Transformations in Syntheses of Acyclic Polyketides (pp.

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Barry Sharpless, The Mechanism of Asymmetric Epoxidation.

AB - The first asymmetric synthesis of 1,2-diepi-alexine and 1,2,7-triepi-australine (both are unknown at present) is described, which utilized the regioselective asymmetric aminohydroxylation (RAA) reaction of the achiral olefin VI, the cross metathesis (CM) reaction of the terminal olefin 8, and the formation and subsequent intramolecular double cyclization (DC) reactions of the epoxides 10 and 11. The C1 stereocenter was diastereoselectively introduced by the reaction of the aldehyde 7 with vinylmagnesium bromide.

Recent Advances in Catalytic Synthesis of Epoxides Mediated by Organometallic Catalysts (pp.

AB - A mixture of Co(salen) macrocycles, prepared via the ring expansion metathesis oligomerization of salen-functionalized cyclooctene monomers, among the most active soluble catalysts for the hydrolytic kinetic resolution (HKR) of terminal epoxides, is exploited as the catalyst in the ring-opening of epoxides using aliphatic alcohols or phenols as nucleophiles, leading to the direct synthesis of optically active α-aryloxy alcohols or α-alkoxy alcohols. The catalyst is compared to other dimeric, oligomeric and monomeric Co(salen) complexes including a pimelate-linked macrocyclic Co(salen) catalyst and a dimeric Co(salen) catalyst referred to as a bisalen. The catalysts that contain multiple Co(salen) units within a single molecular framework allow for substantial decreases in catalyst loading compared with the monomeric catalyst. The cyclooctene-based Co(salen) macrocycle catalyst allows for good activity and enantioselectivity in the ring-opening of terminal epoxides with phenols as nucleophiles, giving enhanced turnover frequencies relative to many literature catalysts. The cyclooctene-based Co(salen) macrocycle catalyst and the bisalen catalysts are shown to be the most active in the asymmetric ring-opening of (±)1,2-epoxyhexane with methanol, out-performing the other catalysts tested. The Co(salen) macrocycle catalyst is recycled 3 times in this reaction with some loss in activity but no noteworthy change in selectivity.

Sharpless, The Discovery of the Asymmetric Epoxidation,

Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols

Zargarian, Synthesis of Optically Active Secondary Allylic Alcohols from Allylsilanes via Successive Asymmetric Dihydroxylation (AD) and Peterson Olefination Reactions, , 34, 2509 (1993

AB - Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (

Sharpless, Asymmetric Epoxidation of Homoallylic Alcohols.

Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols, , , , , ,  and

N2 - Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (

Sharpless, Enantioselective Synthesis of Both Enantiomers of 7,7-Dimethyl-6,8-dioxabicyclo-[3.2.1]octane via Regioselective Asymmetric Dihydroxylation, , 1, 47 (1993) .

Sharpless, Catalytic Asymmetric Synthesis of New Halogenated Chiral Synthons, , 3, 517 (1997).
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  • Application in the Synthesis of Ligands for Asymmetric Catalysis

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The first handbook to focus on the asymmetric synthesis of ..

Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (

reagent in the synthesis of chiral epoxides.

N2 - A mixture of Co(salen) macrocycles, prepared via the ring expansion metathesis oligomerization of salen-functionalized cyclooctene monomers, among the most active soluble catalysts for the hydrolytic kinetic resolution (HKR) of terminal epoxides, is exploited as the catalyst in the ring-opening of epoxides using aliphatic alcohols or phenols as nucleophiles, leading to the direct synthesis of optically active α-aryloxy alcohols or α-alkoxy alcohols. The catalyst is compared to other dimeric, oligomeric and monomeric Co(salen) complexes including a pimelate-linked macrocyclic Co(salen) catalyst and a dimeric Co(salen) catalyst referred to as a bisalen. The catalysts that contain multiple Co(salen) units within a single molecular framework allow for substantial decreases in catalyst loading compared with the monomeric catalyst. The cyclooctene-based Co(salen) macrocycle catalyst allows for good activity and enantioselectivity in the ring-opening of terminal epoxides with phenols as nucleophiles, giving enhanced turnover frequencies relative to many literature catalysts. The cyclooctene-based Co(salen) macrocycle catalyst and the bisalen catalysts are shown to be the most active in the asymmetric ring-opening of (±)1,2-epoxyhexane with methanol, out-performing the other catalysts tested. The Co(salen) macrocycle catalyst is recycled 3 times in this reaction with some loss in activity but no noteworthy change in selectivity.

Asymmetric synthesis of epoxides from aldehydes …

Sharpless, Syntheses and Crystal Structures of the Cinchona Alkaloid Derivatives used as Ligands in the Osmium-Catalyzed Asymmetric Dihydroxylation of Olefins,

Asymmetric Catalysis of Epoxide Ring-Opening …

Although the scope of these reactions is somewhat limited by the necessary presence of strong base in the reaction medium, asymmetric transformations employing chiral lithium amides have been applied to the synthesis of many chiral natural products.

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