Studien zum vorgang der wasserstoffübertragung 24 asymmetrische induktion bei der reduktion von acetophenon-N-benzylimin an der quecksilberkathode mit chiralen leitsalzen

Horner, L.; Skaletz, D. H.

doi:10.1016/s0040-4039(01)98560-0

Cited by 26 publications

(4 citation statements)

References 4 publications

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“…Gansäuer has reported the use of Brintzinger's [ethylenebis(tetrahydroindenyl)]titanium dichloride in similar pinacol couplings, but no comparison can be made with the corresponding bis(indenyl)titanium complex, since its resolution has not been accomplished. When the pinacol coupling is run using manganese metal as the stoichiometric reductant and TMSCl in THF at room temperature, it is catalytic in titanocene dichloride, producing a mixture of unreacted aldehyde and meso- and dl -silyl ethers 11a , b (Scheme ). The silyl ethers can be desilylated using tetrabutylammonium fluoride to give a meso / dl mixture of diols 12a , b .…”

Section: Resultsmentioning

confidence: 99%

Preparation of [2,5-Diisopropylcyclohexane-1,4- bis(indenyl)]titanium Dichloride and [2,5-Diisopropylcyclohexane-1,4-bis(tetrahydroindenyl)]- titanium Dichloride and Their Comparison as Catalysts for the Enantioselective Pinacol Coupling of Benzaldehyde

et al. 2000

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The nonracemic bis(indene) (+)-(1R,2R,4R,5R)-1,4-bis(3′-indenyl)-2,5-diisopropylcyclohexane (10) was synthesized in 60% yield from the addition of indenyllithium to the corresponding bis(methanesulfonate) ester of 2,4-diisopropyl-1,4-cyclohexanediol. Deprotonation of bis(indene) 10 with n-BuLi followed by metalation with TiCl 3 and oxidative workup (HCl, air, chloroform) gave the single stereoisomeric 2,5-diisopropylcyclohexane-1,4-diylbridged bis(indenyl)titanium dichloride 3 in 80% yield. Attempts to form the corresponding bis(indenyl)zirconium dichloride were unsuccessful. Catalytic hydrogenation of bis(indenyl)titanium dichloride 3 gave the 2,5-diisopropylcyclohexane-1,4-diyl-bridged bis(tetrahydroindenyl)titanium dichloride 4 in 76% yield. The solid-state structure of 4 was determined by X-ray crystallographic methods. Nonracemic mixtures of chiral bis(indenyl)titanium dichloride 3 and bis(tetrahydroindenyl)titanium dichloride 4 were examined as catalysts for the pinacol coupling of benzaldehyde in the presence of manganese metal. The enantioselectivities for dihydrobenzoin were 0% with bis(indenyl) 3 and 32% with bis(tetrahydroindenyl) 4 to give the first comparison of enantioselectivities with corresponding bis(indenyl) and bis-(tetrahydroindenyl) complexes. Scheme 1 Scheme 2

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Section: Resultsmentioning

confidence: 99%

Preparation of [2,5-Diisopropylcyclohexane-1,4- bis(indenyl)]titanium Dichloride and [2,5-Diisopropylcyclohexane-1,4-bis(tetrahydroindenyl)]- titanium Dichloride and Their Comparison as Catalysts for the Enantioselective Pinacol Coupling of Benzaldehyde

et al. 2000

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“…A recent article by Wattanakit described several approaches for the development of chiral metal electrodes for enantioselective recognition and asymmetric synthesis developed over the past decade [18]. Concurrent with pioneering works in the field of asymmetric induction in electrochemical reduction on chiral mercury cathodes in the presence of chiral inductors, including tertiary amines, optically active proteins, and alkaloids [19–20], in 1975, Miller’s group reported the first example of the modification of electrodes via covalent binding [21]. They chemically modified air-oxidized graphite electrodes via treatment with thionyl chloride followed by derivatization with ( S )-(−)-phenylalanine methyl ester.…”

Section: Reviewmentioning

confidence: 99%

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

Ghosh

Shinde

Rueping

2019

Beilstein J. Org. Chem.

164

101

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The direct exploitation of ‘electrons’ as reagents in synthetic organic transformations is on the verge of a renaissance by virtue of its greenness, sustainability, atom economy, step economy and inherent safety. Achieving stereocontrol in such organic electrochemical reactions remains a major synthetic challenge and hence demands great expertise. This review provides a comprehensive discussion of the details of stereoselective organic electrochemical reactions along with the synthetic accomplishments achieved with these methods.

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“…However, cost-wise, both additives are not the best options, and the former cannot be recycled, remaining in the solution after isolating the product of interest. [15][16][17][18][19][20][21][22] One example is the study performed with a manganese complex and a zinc working electrode. The authors observed the almost quantitative production of 1-phenylethanol, but the reaction condition includes ammonium salt, CH 3 CN, and closed cell in a dark environment, because the complex is light sensitive.…”

Section: Introductionmentioning

confidence: 99%

“…Good results regarding the selectivity of the reaction were obtained from the addition of ammonium salts as supporting electrolytes, in addition to the use of transition metal catalysts. However, cost‐wise, both additives are not the best options, and the former cannot be recycled, remaining in the solution after isolating the product of interest [15–22] . One example is the study performed with a manganese complex and a zinc working electrode.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Electroreduction of Acetophenone Using Lipase Stabilization: Improved Conversion to 1‐Phenylethanol

et al. 2023

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Few works present effective or viable alternatives to the problem of the electroreduction of acetophenone which usually leads to the pinacol dimer as a primary product in addition to 1‐phenylethanol. Here, various lipases were applied in acetophenone electroreduction. The optimized reaction conditions are tin/lead (63 : 37) combined working electrode coated with Nafion film modified with lipase from Thermomyces lanuginosus, a platinum counter electrode, applied potential of −2.0 V vs. Ag/AgCl (KCl 3.0 mol L−1), acetate buffer (0.1 mol L−1) pH 5.0 in 4 hours, and led to the formation of 87.8 % of 1‐phenylethanol. The same working electrode was used five times over five days, and the conversion remained constant. A voltammetric study indicates an alteration of the electroreduction mechanism in the presence of the cited lipase. Adding lipase from Thermomyces lanuginosus directly in the medium immobilized in a clay mineral or in silica gel (Lipolase 100T) resulted in even higher conversions (93.2–93.9 %). The modified electrode improved the methodology regarding enzyme stability, process reproducibility, and material reusability.

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Studien zum vorgang der wasserstoffübertragung 24 asymmetrische induktion bei der reduktion von acetophenon-N-benzylimin an der quecksilberkathode mit chiralen leitsalzen

Cited by 26 publications

References 4 publications

Preparation of [2,5-Diisopropylcyclohexane-1,4- bis(indenyl)]titanium Dichloride and [2,5-Diisopropylcyclohexane-1,4-bis(tetrahydroindenyl)]- titanium Dichloride and Their Comparison as Catalysts for the Enantioselective Pinacol Coupling of Benzaldehyde

Preparation of [2,5-Diisopropylcyclohexane-1,4- bis(indenyl)]titanium Dichloride and [2,5-Diisopropylcyclohexane-1,4-bis(tetrahydroindenyl)]- titanium Dichloride and Their Comparison as Catalysts for the Enantioselective Pinacol Coupling of Benzaldehyde

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

Enhanced Electroreduction of Acetophenone Using Lipase Stabilization: Improved Conversion to 1‐Phenylethanol

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