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.

scholarly journals New Bifunctional Bis(azairidacycle) with Axial Chirality via Double Cyclometalation of 2,2′-Bis(aminomethyl)-1,1′-binaphthyl

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1165
Author(s):  
Yasuhiro Sato ◽  
Yuichi Kawata ◽  
Shungo Yasui ◽  
Yoshihito Kayaki ◽  
Takao Ikariya
Keyword(s):  
Hydrogen Transfer ◽  
Bond Cleavage ◽  
Enantiomeric Excess ◽  
Transfer Hydrogenation ◽  
Catalyst Precursor ◽  
Asymmetric Catalysts ◽  
Axially Chiral ◽  
Diastereomeric Mixture ◽  
Raney Ni ◽  
Half Sandwich

As a candidate for bifunctional asymmetric catalysts containing a half-sandwich C–N chelating Ir(III) framework (azairidacycle), a dinuclear Ir complex with an axially chiral linkage is newly designed. An expedient synthesis of chiral 2,2′-bis(aminomethyl)-1,1′-binaphthyl (1) from 1,1-bi-2-naphthol (BINOL) was accomplished by a three-step process involving nickel-catalyzed cyanation and subsequent reduction with Raney-Ni and KBH4. The reaction of (S)-1 with an equimolar amount of [IrCl2Cp*]2 (Cp* = η5–C5(CH3)5) in the presence of sodium acetate in acetonitrile at 80 °C gave a diastereomeric mixture of new dinuclear dichloridodiiridium complexes (5) through the double C–H bond cleavage, as confirmed by 1H NMR spectroscopy. A loss of the central chirality on the Ir centers of 5 was demonstrated by treatment with KOC(CH3)3 to generate the corresponding 16e amidoiridium complex 6. The following hydrogen transfer from 2-propanol to 6 provided diastereomers of hydrido(amine)iridium retaining the bis(azairidacycle) architecture. The dinuclear chlorido(amine)iridium 5 can serve as a catalyst precursor for the asymmetric transfer hydrogenation of acetophenone with a substrate to a catalyst ratio of 200 in the presence of KOC(CH3)3 in 2-propanol, leading to (S)-1-phenylethanol with up to an enantiomeric excess (ee) of 67%.

scholarly journals Pd(0) encapsulated nanocatalysts as superior catalytic systems for Pd-catalyzed organic transformations

RSC Advances ◽  
2016 ◽  
Vol 6 (91) ◽  
pp. 88588-88624 ◽  
Author(s):  
S. Sadjadi ◽  
M. M. Heravi
Keyword(s):  
Chemical Reactions ◽  
Organic Transformations ◽  
Catalytic Systems

In the last decade, Pd(0) nanoparticles have attracted increasing attention due to their outstanding utility as nanocatalysts in a wide variety of key chemical reactions.

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%.

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 Catalytic Conversion of Carbon Dioxide through C-N Bond Formation

Molecules ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 182 ◽  
Author(s):  
Jing-Yuan Li ◽  
Qing-Wen Song ◽  
Kan Zhang ◽  
Ping Liu
Keyword(s):  
Carbon Dioxide ◽  
Catalytic Mechanism ◽  
Bond Formation ◽  
Catalytic Efficiency ◽  
Chemical Fixation ◽  
Catalytic Systems ◽  
Formation Reaction ◽  
Metal Free ◽  
The Past ◽  
Regulatory Strategies

From the viewpoint of green chemistry and sustainable development, it is of great significance to synthesize chemicals from CO2 as C1 source through C-N bond formation. During the past several decade years, many studies on C-N bond formation reaction were involved, and many efforts have been made on the theory. Nevertheless, several great challenges such as thermodynamic limitation, low catalytic efficiency and selectivity, and high pressure etc. are still suffered. Herein, recent advances are highlighted on the development of catalytic methods for chemical fixation of CO2 to various chemicals through C-N bond formation. Meanwhile, the catalytic systems (metal and metal-free catalysis), strategies and catalytic mechanism are summarized and discussed in detail. Besides, this review also covers some novel synthetic strategies to urethanes based on amines and CO2. Finally, the regulatory strategies on functionalization of CO2 for N-methylation/N-formylation of amines with phenylsilane and heterogeneous catalysis N-methylation of amines with CO2 and H2 are emphasized.

The controllable synthesis of ultrafine one-dimensional small-molecule semiconducting nanocrystals in surfactant-assisted wet chemical reactions and their confinement effect

2017 ◽  
Vol 5 (25) ◽  
pp. 6377-6385 ◽  
Author(s):  
Jiannan Pan ◽  
Longtian Kang ◽  
Ping Huang ◽  
Ziyan Jia ◽  
Jingjing Liu ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Small Molecule ◽  
Confinement Effect ◽  
Controllable Synthesis ◽  
One Dimensional ◽  
Wet Chemical ◽  
Transfer State ◽  
Surfactant Assisted

Ultrafine 1D nanocrystals of (FeTPP)2O have been successfully synthesized in a CTAB-assisted wet chemical reaction. The 1D confinement effect of the intermolecular charge transfer state was found.

scholarly journals Novel Bispidine-Monoterpene Conjugates—Synthesis and Application as Ligands for the Catalytic Ethylation of Chalcones

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7539
Author(s):  
Evgeniy V. Suslov ◽  
Konstantin Y. Ponomarev ◽  
Oxana S. Patrusheva ◽  
Sergey O. Kuranov ◽  
Alina A. Okhina ◽  
...  
Keyword(s):  
Double Bond ◽  
Chromatographic Analysis ◽  
Enantiomeric Excess ◽  
Catalytic Systems ◽  
First Time

A number of new chiral bispidines containing monoterpenoid fragments have been obtained. The bispidines were studied as ligands for Ni-catalyzed addition of diethylzinc to chalcones. The conditions for chromatographic analysis by HPLC-UV were developed, in which the peaks of the enantiomers of all synthesized chiral products were separated, which made it possible to determine the enantiomeric excess of the resulting mixture. It was demonstrated that bispidine-monoterpenoid conjugates can be used as the ligands for diethylzinc addition to chalcone C=C double bond but not as inducers of chirality. Besides products of ethylation, formation of products of formal hydrogenation of the chalcone C=C double bond was observed in all cases. Note, that this formation of hydrogenation products in significant amounts in the presence of such catalytic systems was found for the first time. A tentative scheme explaining the formation of all products was proposed.

scholarly journals Secretory expression of cyclohexanone monooxygenase by methylotrophic yeast for efficient omeprazole sulfide bio-oxidation

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Ya-Jing Li ◽  
Yu-Cong Zheng ◽  
Qiang Geng ◽  
Feng Liu ◽  
Zhi-Jun Zhang ◽  
...  
Keyword(s):  
Fermentation Broth ◽  
Enantiomeric Excess ◽  
Catalytic Efficiency ◽  
Methylotrophic Yeast ◽  
Fold Increase ◽  
Dry Weight ◽  
Cyclohexanone Monooxygenase ◽  
E Coli ◽  
A Cell ◽  
Omeprazole Sulfide

AbstractProchiral pyrmetazole can be asymmetrically oxidized into (S)-omeprazole, a proton pump inhibitor that is used to treat gastroesophageal reflux, by an engineered cyclohexanone monooxygenase (CHMOAcineto-Mut) that has high stereoselectivity. CHMOAcineto-Mut is produced by heterologous expression in Escherichia coli, where it is expressed intracellularly. Thus, isolating this useful biocatalyst requires tedious cell disruption and subsequent purification, which hinders its use for industrial purposes. Here, we report the extracellular production of CHMOAcineto-Mut by a methylotrophic yeast, Pichia pastoris, for the first time. The recombinant CHMOAcineto-Mut expressed by P. pastoris showed a higher flavin occupation rate than that produced by E. coli, and this was accompanied by a 3.2-fold increase in catalytic efficiency. At a cell density of 150 g/L cell dry weight, we achieved a recombinant CHMOAcineto-Mut production rate of 1,700 U/L, representing approximately 85% of the total protein secreted into the fermentation broth. By directly employing the pH adjusted supernatant as a biocatalyst, we were able to almost completely transform 10 g/L of pyrmetazole into the corresponding (S)-sulfoxide, with  >  99% enantiomeric excess.

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