Dimethyldioxirane Oxidation of Titanium Enolates: Diastereoselective .alpha.-Hydroxylations

Adam, Waldemar; Mueller, Michael; Prechtl, Frank

doi:10.1021/jo00088a015

Cited by 56 publications

(18 citation statements)

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“…To explore this, we looked at intercepting the ostensibly formed silyl enol ether 7 (Scheme ). In this context, instead of treating the reaction mixture with HCl after alkyne addition, it was cooled to −78 °C and 3 equivalents of dimethyldioxirane were added directly to the reaction vessel to effect Rubottom oxidation . Under these conditions, the corresponding α‐hydroxyketone 10 was isolated as a single diastereomer in 68 % overall yield.…”

Section: Methodsmentioning

confidence: 99%

A Facile Enantioselective Alkynylation of Chromones

2019

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The first catalytic enantioselective alkynylation of chromones is reported. In this process, chromones are silylated to form silyloxybenzopyrylium ions that lead to silyl enol ethers after Cu‐catalyzed alkyne addition using StackPhos as a ligand. The outcome of the reaction is impacted by distal ligand substituents with differing electronic character and it was found that successful reactions could be achieved with different ligand congeners by using different solvents. This sequence enables access to different products by protonation or further functionalization, thus increasing complexity in a divergent manner. The transformation is high yielding over a broad scope to provide a variety of useful chromanones in high enantioselectivity.

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Section: Methodsmentioning

confidence: 99%

A Facile Enantioselective Alkynylation of Chromones

2019

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“…There are many strategies, both chemical and biochemical, leading to the synthesis of enantiomerically enriched α-hydroxy ketones. Hydrobenzoins may be prepared by chemical means using oxidation of prochiral enolates in a reaction catalyzed by chiral oxidants, dihydroxylation of silyl enol ethers, RuO 4 -catalyzed reaction of ketohydroxylation of olefins, mono-oxidation of diols using a chiral catalyst; e.g., copper, or oxidation of racemic benzoins by a chiral iron or cobalt complex [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. In addition, α-hydroxyketones can be obtained by direct α-oxygenation of ketones in the presence of chiral amino acids ( l -proline, l -alanine) and by benzoin condensation catalyzed by chiral thiazolium or triazolium salts (chiral metallophosphites) [ 18 , 19 , 20 , 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

Microbial Synthesis of (S)- and (R)-Benzoin in Enantioselective Desymmetrization and Deracemization Catalyzed by Aureobasidium pullulans Included in the Blossom Protect™ Agent

et al. 2021

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In this study, we examined the Aureobasidium pullulans strains DSM 14940 and DSM 14941 included in the Blossom Protect™ agent to be used in the bioreduction reaction of a symmetrical dicarbonyl compound. Both chiral 2-hydroxy-1,2-diphenylethanone antipodes were obtained with a high enantiomeric purity. Mild conditions (phosphate buffer [pH 7.0, 7.2], 30 °C) were successfully employed in the synthesis of (S)-benzoin using two different methodologies: benzyl desymmetrization and rac-benzoin deracemization. Bioreduction carried out with higher reagent concentrations, lower pH values and prolonged reaction time, and in the presence of additives, enabled enrichment of the reaction mixture with (R)-benzoin. The described procedure is a potentially useful tool in the synthesis of chiral building blocks with a defined configuration in a simple and economical process with a lower environmental impact, enabling one-pot biotransformation.

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“…Oxone ® (potassium peroxymonosulfate) is a safe and inexpensive oxidizing reagent of widespread application, including the oxidation of acetone to give dimethyldioxirane (DMD), an unstable oxidant employed in the α-hydroxylation of β-dicarbonyl compounds. 13,14 However, DMD itself is reluctant to oxidize α-substituted malonates, with high conversions to the corresponding α-hydroxy-β-dicarbonyls being achieved only in the presence of a nickel catalyst. 15 To circumvent the tedious preparation of DMD solutions and the risks associated with their handling, Zhang and co-workers 16 reported the direct use of Oxone ® for the α-hydroxylation of a great variety of cyclic β-keto esters, β-keto amides, and β-diketones in aqueous medium at 60 °C.…”

Section: Introductionmentioning

confidence: 99%

Oxone®-Mediated Direct α-Hydroxylation of β-Dicarbonyl Compounds: Racemic Synthesis of Harzialactone A

Sá¹,

Peterle²,

Marques³

2019

J. Braz. Chem. Soc.

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An environmentally benign method is described for the α-hydroxylation of malonates and cyclic analogues in aqueous medium at room temperature under mild conditions, based on the in situ generation of dimethyldioxirane through the combination of acetone and Oxone ® . This procedure was found to be substrate-dependent and was successfully performed to provide α-hydroxylated γ-lactones. To demonstrate the synthetic potential of this mild α-hydroxylation, two different concise routes were developed to synthesize harzialactone A in the racemic form with a moderate (3:1) diastereomeric ratio.Scheme 5. Two strategies for the racemic synthesis of harzialactone A (4a) starting with epoxide 2a.

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Dimethyldioxirane Oxidation of Titanium Enolates: Diastereoselective .alpha.-Hydroxylations

Cited by 56 publications

References 0 publications

A Facile Enantioselective Alkynylation of Chromones

A Facile Enantioselective Alkynylation of Chromones

Microbial Synthesis of (S)- and (R)-Benzoin in Enantioselective Desymmetrization and Deracemization Catalyzed by Aureobasidium pullulans Included in the Blossom Protect™ Agent

Oxone®-Mediated Direct α-Hydroxylation of β-Dicarbonyl Compounds: Racemic Synthesis of Harzialactone A

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