Asymmetric Catalytic Ketone Hydrogenation: Relating Substrate Structure and Product Enantiomeric Excess Using QSPR

2005 ◽  
Vol 24 (1) ◽  
pp. 94-98 ◽  
Author(s):  
Johannes B. van der Linden ◽  
Erik-Jan Ras ◽  
Simone M. Hooijschuur ◽  
Guido M. Klaus ◽  
Niels T. Luchters ◽  
...  
Keyword(s):  
Enantiomeric Excess ◽  
Asymmetric Catalytic ◽  
Substrate Structure ◽  
Ketone Hydrogenation

scholarly journals Synthesis of GO-SalenMn and Asymmetric Catalytic Olefin Epoxidation

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 824
Author(s):  
Fengqin Wang ◽  
Tiankui Huang ◽  
Shurong Rao ◽  
Qian Chen ◽  
Cheng Huang ◽  
...  
Keyword(s):  
Enantiomeric Excess ◽  
Catalytic Performance ◽  
Hydroxyl Group ◽  
Asymmetric Catalytic ◽  
Axial Coordination ◽  
Catalyst Carrier ◽  
Ft Ir ◽  
Repeated Use ◽  
Number Of Cycles ◽  
Methyl Styrene

Graphene oxide (GO) was used as a catalyst carrier, and after the hydroxyl group in GO was modified by 3-aminopropyltrimethoxysilane (MPTMS), axial coordination and immobilization with homogeneous chiral salenMnCl catalyst were carried out. The immobilized catalysts were characterized in detail by FT–IR, TG–DSC, XPS, EDS, SEM, X-ray, and AAS, and the successful preparation of GO-salenMn was confirmed. Subsequently, the catalytic performance of GO-salenMn for asymmetric epoxidation of α-methyl-styrene, styrene, and indene was examined, and it was observed that GO-salenMn could efficiently catalyze the epoxidation of olefins under an m-CPBA/NMO oxidation system. In addition, α-methyl-styrene was used as a substrate to investigate the recycling performance of GO-salenMn. After repeated use for three times, the catalytic activity and enantioselectivity did not significantly change, and the conversion was still greater than 99%. As the number of cycles increased, the enantioselectivity and chemoselectivity gradually decreased, but even after 10 cycles, the enantiomeric excess was 52%, which was higher than that of the homogeneous counterpart under the same conditions. However, compared to fresh catalysts, the yield decreased from 96.9 to 55.6%.

scholarly journals Can we measure catalyst efficiency in asymmetric chemical reactions? A theoretical approach

2009 ◽  
Vol 5 ◽  
Author(s):  
Shaimaa El-Fayyoumy ◽  
Matthew H Todd ◽  
Christopher J Richards
Keyword(s):  
Chemical Reactions ◽  
Small Molecule ◽  
Enantiomeric Excess ◽  
Catalytic Efficiency ◽  
Catalytic Systems ◽  
Asymmetric Catalysts ◽  
Asymmetric Catalytic ◽  
Short Period ◽  
Asymmetric Catalyst ◽  
Catalyst Efficiency

Small molecule asymmetric catalysts are often described as being “good” or “bad” but to date there has been no way of comparing catalyst efficiency quantitatively. We define a simple formula, Asymmetric Catalyst Efficiency (ACE), that allows for such a comparison. We propose that a catalyst is more efficient if fewer atoms are utilised to give a product in a required enantiomeric excess. We illustrate this concept by analysing several well-known asymmetric catalytic chemical reactions carried out in academic laboratories, and compare small molecule catalysts with enzymes. We conclude that ACE is a useful descriptor for the comparison of diverse catalytic systems. It is also noteworthy that, despite the relatively short period of investigation into small molecule catalysts, they are competitive with enzymes with regards to this measure of catalytic efficiency.

Solvent-Induced Chirality in the Hydroboration of Ketones

2008 ◽  
Vol 61 (6) ◽  
pp. 414 ◽  
Author(s):  
Christoph Baldauf ◽  
Nina Dickerhof ◽  
Stefan H. Hüttenhain ◽  
Stefanie Kern ◽  
Nancy Krummrich ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Methyl Ester ◽  
Lewis Acids ◽  
Enantiomeric Excess ◽  
Acid Methyl Ester ◽  
Asymmetric Induction ◽  
Aromatic Ketones ◽  
Positive Effects ◽  
Substrate Structure ◽  
Acid Methyl

The influence of the systematic variation of chiral solvents and of diverse Lewis acids on the asymmetric induction of the hydroboration of acetophenone has been studied. None of the solvents used could surpass lactic acid methyl ester, and for the Lewis acids, ZnCl2 and ZnI2 showed positive effects on the enantiomeric excess (ee) and the conversion. Also, the effect of the substrate structure was investigated by comparing the conversion and ee of eight different ketones. Apparently, the achievable asymmetric induction was higher with aromatic ketones.

Room Temperature Flow Electrochemistry as a Means of Retaining the “Memory of Chirality” via Hofer Moest Type Reaction

2020 ◽  
Author(s):  
Tomas Hardwick ◽  
Rossana Cicala ◽  
Nisar Ahmed
Keyword(s):  
Continuous Flow ◽  
Room Temperature ◽  
Biological Activities ◽  
Supporting Electrolyte ◽  
Enantiomeric Excess ◽  
Flow Chemistry ◽  
Batch Processes ◽  
Enabling Technology ◽  
Chiral Compounds ◽  
Memory Of Chirality

<p>Many chiral compounds have become of great interest to the pharmaceutical industry as they possess various biological activities. Concurrently, the concept of “memory of chirality” has been proven as a powerful tool in asymmetric synthesis, while flow chemistry has begun its rise as a new enabling technology to add to the ever increasing arsenal of techniques available to the modern day chemist. Here, we have employed a new simple electrochemical microreactor design to oxidise an L-proline derivative at room temperature in continuous flow. Flow performed in microreactors offers up a number of benefits allowing reactions to be performed in a more convenient and safer manner, and even allow electrochemical reactions to take place without a supporting electrolyte due to a very short interelectrode distance. By the comparison of electrochemical oxidations in batch and flow we have found that continuous flow is able to outperform its batch counterpart, producing a good yield (71%) and a better enantiomeric excess (64%) than batch with a 98% conversion. We have, therefore, provided evidence that continuous flow chemistry has the potential to act as a new enabling technology to replace some aspects of conventional batch processes. </p>

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

Impact of Substrate Structure Changes Caused by Thermal Treatment on Hydrolysis Rate Within Anaerobic Digestion

2018 ◽  
Vol 2018 (18) ◽  
pp. 387-392
Author(s):  
Elizabeth Manning ◽  
Adrian Romero ◽  
Baoqiang Li ◽  
Ahmed Al-Omari ◽  
Matthew Higgins ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Thermal Treatment ◽  
Hydrolysis Rate ◽  
Substrate Structure ◽  
Structure Changes

Synergistic Cu/Pd-Catalyzed Asymmetric Allylation: A Facile Access to α-Quaternary Cysteine Derivatives

2021 ◽  
Author(s):  
Hui-Min Wu ◽  
Zongpeng Zhang ◽  
Liang Wei ◽  
Xiu-Qin Dong ◽  
Chun-Jiang Wang
Keyword(s):  
Asymmetric Allylation ◽  
Synthetic Methodology ◽  
Asymmetric Catalytic

An efficient synthetic methodology to access biologically important and synthetically useful α-quaternary cysteine derivatives via asymmetric catalytic α-allylation of readily available 2-thiazoline-4-carboxylates was successfully developed through the synergistic Cu/Pd catalytic...

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