Asymmetric epoxidation using hydrogen peroxide (H2O2) as primary oxidant

Shu, Lianhe; Shi, Yian

doi:10.1016/s0040-4039(99)01814-6

Cited by 93 publications

(35 citation statements)

References 35 publications

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“…Treatment of bromide 25 with n –BuLi enacted halogen metal exchange and subsequent reaction with geranyl bromide installed the geranyl chain to provide compound 26 in 86% yield. A Shi epoxidation 12 of geranylated arene 26 was observed upon treatment with hydrogen peroxide in the presence of sugar catalyst 27 and acetonitrile in buffered solution to afford epoxide 28 in a modest yield but excellent enantioselectivity ( vide infra ). In addition this application of the Shi epoxidation generally results in recovery of 33–54% of the starting olefin so yields based on recovered starting material are very attractive.…”

Section: Resultsmentioning

confidence: 99%

“…Treatment of compound 36 with TsOH resulted in cleavage of the three MOM groups and provided the new schweinfurthin analogue 10 in a modest yield. Finally, standard cleavage of the silyl protecting group of tricycle 20 followed by MnO 2 oxidation to the corresponding aldehyde represents a formal synthesis of both schweinfurthin F ( 7 ) 12 and 3dSB ( 11 ). 16 Synthesis of 3dSB through this BF 3 ·Et 2 O mediated cyclization shows consistent transmission of stereochemical integrity from the epoxide through the cyclization, in parallel with our work using protic acids.…”

Section: Resultsmentioning

confidence: 99%

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BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

Neighbors²,

2008

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The total synthesis of the natural stilbene (+)-schweinfurthin G (8) has been accomplished through a sequence based on an efficient cationic cascade cyclization. This cascade process is initiated by Lewis acid promoted ring opening of an epoxide and terminated through a novel reaction with a phenolic oxygen “protected” as its MOM ether. Several Lewis acids have been examined for their ability to induce this new reaction, and BF3·Et2O was found to be the most effective. The only major by-product under these conditions was one where the expected secondary alcohol was found as its MOM ether derivative (e.g. 30). While this by-product could be converted to the original target compound through hydrolysis, it also could be employed as a protected alcohol to allow preparation of a benzylic phosphonate (43) without dehydration of the secondary alcohol. The resulting phosphonate was employed in a Horner-Wadsworth-Emmons condensation with an aldehyde representing the right half of the target compounds, an approach complementary to previous studies based on condensation of a right half phosphonate and a left half aldehyde.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

Neighbors²,

2008

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“…Shi and co-workers reported that a fructose-derived ketone promoted epoxidation using aqueous hydrogen peroxide in acetonitrile with high enantioselectivity, albeit with moderate turnover number (TON). [6] Jørgensen and co-workers reported highly enantioselective epoxidation of a,b-unsaturated aldehydes using an organocatalyst in the presence of aqueous hydrogen peroxide. [7] We have recently disclosed that a di-m-oxo-Ti-A C H T U N G T R E N N U N G (salalen) (salalen: half-reduced salen) complex serves as an efficient catalyst for enantioselective epoxidation using aqueous hydrogen peroxide.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Metal–(Pentadentate‐Salen) Complexes: Asymmetric Epoxidation with Aqueous Hydrogen Peroxide and Asymmetric Cyclopropanation (salenH₂: N,N′‐bis(salicylidene)ethylene‐1,2‐diamine)

Shitama

Katsuki

2007

Chemistry A European J

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It is known that the rates and stereochemical outcomes of epoxidations and cyclopropanations using a metallosalen (salenH(2): N,N'-bis(salicylidene)ethylene-1,2-diamine) complex as catalyst are affected by a trans effect of the apical ligand of the complex. By taking into consideration this trans effect, we have synthesized optically active pentadentate salen ligands bearing an imidazole or pyridine derivative as the fifth coordinating group, and have prepared the corresponding manganese(III) and cobalt(II) complexes, in which the fifth ligand is expected to intramolecularly coordinate to the metal center and exert a trans effect. Indeed, high enantioselectivity has been achieved in epoxidations using aqueous hydrogen peroxide as the terminal oxidant and in cyclopropanations with these complexes as catalysts. In general, metallosalen-catalyzed reactions have been carried out in the presence of an excess of a donor ligand; however, the present reactions do not need the addition of any extra donor ligand.

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“…Importantly, in the absence of the ketone catalyst, <5% conversion was observed, suggesting that the ketone is indeed generating a dioxirane in situ as the active catalyst species, in analogy to many other reports. 16 It is also interesting to note that while the ketone catalyst is obtained as a mixture of the ketone and hydrated species, there appear to be no negative effects observed on the reactivity and turnover of the catalyst, presumably since either may enter into the necessary catalytic cycle. For example, when purified via reversed-phase chromatography, the catalyst is obtained as a 1:2 mixture of the ketone and hydrate.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and evaluation of phenylalanine-derived trifluoromethyl ketones for peptide-based oxidation catalysis

Featherston¹,

Miller²

2016

Bioorganic & Medicinal Chemistry

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We report the synthesis of phenylalanine-derived trifluoromethyl ketones for the in situ generation of dioxiranes for the purpose of oxidation catalysis. The key features of this synthesis include the use of a masked ketone strategy and a Negishi cross -coupling to access the parent amino acid. The derivatives can be readily incorporated into a peptide for use in oxidation chemistry and exhibit good stability and reactivity.

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Asymmetric epoxidation using hydrogen peroxide (H2O2) as primary oxidant

Cited by 93 publications

References 35 publications

BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

Synthesis of Metal–(Pentadentate‐Salen) Complexes: Asymmetric Epoxidation with Aqueous Hydrogen Peroxide and Asymmetric Cyclopropanation (salenH₂: N,N′‐bis(salicylidene)ethylene‐1,2‐diamine)

Synthesis and evaluation of phenylalanine-derived trifluoromethyl ketones for peptide-based oxidation catalysis

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Asymmetric epoxidation using hydrogen peroxide (H2O2) as primary oxidant

Cited by 93 publications

References 35 publications

BF3·Et2O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

BF3·Et2O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

Synthesis of Metal–(Pentadentate‐Salen) Complexes: Asymmetric Epoxidation with Aqueous Hydrogen Peroxide and Asymmetric Cyclopropanation (salenH2: N,N′‐bis(salicylidene)ethylene‐1,2‐diamine)

Synthesis and evaluation of phenylalanine-derived trifluoromethyl ketones for peptide-based oxidation catalysis

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Product

Resources

About

BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

BF₃·Et₂O-Mediated Cascade Cyclizations: Synthesis of Schweinfurthins F and G

Synthesis of Metal–(Pentadentate‐Salen) Complexes: Asymmetric Epoxidation with Aqueous Hydrogen Peroxide and Asymmetric Cyclopropanation (salenH₂: N,N′‐bis(salicylidene)ethylene‐1,2‐diamine)