Gold-Catalyzed Cyanosilylation Reaction: Homogeneous and Heterogeneous Pathways

Cho, Woo ,Kyung,Lee, Jungkyu ,K.,Kang, Sung ,Min,Chi, Young Shik,Lee, Hee-Seung,Choi, Insung ,S. Wiley - VCH Verlag GmbH & Co. KGaA 2007 Chemistry Vol.13 No.22

<P>Gold had been considered to be an extremely inert metal, but recently it was found that nanometer-sized gold particles on metal-oxide supports acted as catalysts for simple organic reactions, such as oxidation and hydrogenation, even at or below room temperature. Herein, we report that gold nanoparticles (AuNPs) of zero oxidation state (Au<SUP>0</SUP>) are catalytically active for a C&n.bond;C bond-forming reaction, the cyanosilylation of aldehydes. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt % loading of AuNPs. The reactions of aromatic aldehydes were almost quantitative, except for benzaldehyde derivatives containing the electron-withdrawing NO<SUB>2</SUB> group, and α,β-unsaturated aromatic aldehydes were the most reactive substrates. The reactions also went smoothly for aliphatic aldehydes. Mechanistic studies indicated that the reactions proceeded both homogeneously and heterogeneously: homogeneous catalysis by leached gold species and heterogeneous catalysis by the adsorption of the reactants (aldehydes and trimethylsilyl cyanide) onto AuNPs. The ratio of homogeneous and heterogeneous catalysis was estimated to be ≈4:1.</P> <B>Graphic Abstract</B> <P>Good as gold: Gold nanoparticles (AuNPs) were found to be catalytically active for a C&n.bond;C bond-forming reaction, the cyanosilylation of aldehydes. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt % loading of AuNPs (see scheme; TMS: trimethylsilyl). Detailed experiments indicate that the reaction occurs by a combined pathway of heterogeneous and homogeneous catalysis. <img src='wiley_img/09476539-2007-13-22-CHEM200601791-content.gif' alt='wiley_img/09476539-2007-13-22-CHEM200601791-content'> </P>

Substrate Ground State Binding Energy Concentration Is Realized as Transition State Stabilization in Physiological Enzyme Catalysis

Britt, Billy Mark Korean Society for Biochemistry and Molecular Biol 2004 Journal of biochemistry and molecular biology Vol.37 No.5

Previously published kinetic data on the interactions of seventeen different enzymes with their physiological substrates are re-examined in order to understand the connection between ground state binding energy and transition state stabilization of the enzyme-catalyzed reactions. When the substrate ground state binding energies are normalized by the substrate molar volumes, binding of the substrate to the enzyme active site may be thought of as an energy concentration interaction; that is, binding of the substrate ground state brings in a certain concentration of energy. When kinetic data of the enzyme/substrate interactions are analyzed from this point of view, the following relationships are discovered: 1) smaller substrates possess more binding energy concentrations than do larger substrates with the effect dropping off exponentially, 2) larger enzymes (relative to substrate size) bind both the ground and transition states more tightly than smaller enzymes, and 3) high substrate ground state binding energy concentration is associated with greater reaction transition state stabilization. It is proposed that these observations are inconsistent with the conventional (Haldane) view of enzyme catalysis and are better reconciled with the shifting specificity model for enzyme catalysis.

Photocatalytic hydrogen peroxide production by anthraquinone-augmented polymeric carbon nitride

Kim, Hyoung-il,Choi, Yeoseon,Hu, Shu,Choi, Wonyong,Kim, Jae-Hong Elsevier 2018 Applied Catalysis B Vol.229 No.-

<P><B>Abstract</B></P> <P>We describe the exploitation of the selective catalytic property of anthraquinone (AQ) for solar photocatalytic synthesis of hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) as a green, sustainable alternative to organic-solvent-based and energy-intensive industry-benchmark processes that also rely on AQ catalysis. We accomplished this by anchoring AQ onto polymeric carbon nitride (C<SUB>3</SUB>N<SUB>4</SUB>), a metal-free visible light photocatalyst (band gap energy = 2.7 eV), that has been previously demonstrated for selective H<SUB>2</SUB>O<SUB>2</SUB> synthesis. A net H<SUB>2</SUB>O<SUB>2</SUB> production rate of 361 μmol g<SUP>−1</SUP> h<SUP>−1</SUP> and an apparent quantum yield (AQY) of 19.5% at 380 nm excitation were achieved using AQ-augmented C<SUB>3</SUB>N<SUB>4</SUB> under simulated 1-sun illumination in the presence of an organic electron donor (2-propanol); these results were 4.4-fold and 8.3-fold higher than those reported for bare C<SUB>3</SUB>N<SUB>4</SUB>, respectively. A suite of experimental analyses confirmed the unique roles of AQ co-catalysis in (i) capturing electrons from the conduction band of C<SUB>3</SUB>N<SUB>4</SUB>, thereby reducing futile exciton recombination, which is otherwise prevalent in bare C<SUB>3</SUB>N<SUB>4</SUB>; (ii) effectively mediating electron transfer to drive hydrogenation reaction to form anthrahydroquinone (AQH<SUB>2</SUB>) from AQ; and (iii) catalyzing oxygen reduction to H<SUB>2</SUB>O<SUB>2</SUB> through the dehydrogenation of AQH<SUB>2</SUB> back to AQ, resulting in the facile and selective formation of H<SUB>2</SUB>O<SUB>2</SUB>. In addition, the reduced decomposition of produced H<SUB>2</SUB>O<SUB>2</SUB> by the C<SUB>3</SUB>N<SUB>4</SUB>/AQ composite photocatalysts, when compared to bare C<SUB>3</SUB>N<SUB>4</SUB> or C<SUB>3</SUB>N<SUB>4</SUB> composited with common metallic co-catalysts such as Pt and Ag, was found to contribute to the significant enhancement in H<SUB>2</SUB>O<SUB>2</SUB> production through the oxidation of both organic and water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anthraquinone from industrial H<SUB>2</SUB>O<SUB>2</SUB> production processes was adopted as a co-catalyst for the photocatalytic H<SUB>2</SUB>O<SUB>2</SUB> production. </LI> <LI> Molecular anthraquinone catalysts were augmented onto heterogeneous surfaces of polymeric carbon nitride. </LI> <LI> The photocatalytic H<SUB>2</SUB>O<SUB>2</SUB> production was significantly improved by anchoring anthraquinone onto polymeric carbon nitride. </LI> <LI> Anthraquinone’s hydration/dehydration reactions were able to provide outstanding selectivity for the formation of H<SUB>2</SUB>O<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Environmental plasma-catalysis for the energy-efficient treatment of volatile organic compounds

Quang Hung Trinh,목영선 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3

Nonthermal plasma (NTP) coupled with catalysis is a promising technique for the abatement of dilute volatile organic compounds (VOCs), because it is operable under mild reaction conditions, i.e., low temperature and atmospheric pressure. This review addresses the mechanistic aspects of catalyst activation by NTP, such as the generation and fixation of reactive species, facilitation of redox cycles, photocatalysis, and local heating, to clarify the combined effects of plasma and catalysis. The plasma-catalytic removal of VOCs preferentially requires the catalyst to have a large specific surface area, high surface oxygen storage capacity, and to be highly reducible. The energy consumption and deactivation of catalysts are considered by comparing continuous and cyclic operations in terms of specific input energy, VOC removal and energy efficiencies, and byproduct formation. Based on the information in the literature, a plasma-catalytic system operating in cyclic adsorption-oxidation mode is recommended for the treatment of air contaminated by dilute VOCs. Finally, the effects of NTP on the regeneration of deactivated catalysts are also discussed.

Substrate Ground State Binding Energy Concentration Is Realized as Transition State Stabilization in Physiological Enzyme Catalysis

( Billy Mark Britt ) 생화학분자생물학회 2004 BMB Reports Vol.37 No.5

Previously published kinetic data on the interactions of seventeen different enzymes with their physiological substrates are re-examined in order to understand the connection between ground state binding energy and transition state stabilization of the enzyme-catalyzed reactions. When the substrate ground state binding energies are normalized by the substrate molar volumes, binding of the substrate to the enzyme active site may be thought of as an energy concentration interaction; that is, binding of the substrate ground state brings in a certain concentration of energy. When kinetic data of the enzyme/ substrate interactions are analyzed from this point of view, the following relationships are discovered: 1) smaller substrates possess more binding energy concentrations than do larger substrates with the effect dropping off exponentially, 2) larger enzymes (relative to substrate size) bind both the ground and transition states more tightly than smaller enzymes, and 3) high substrate ground state binding energy concentration is associated with greater reaction transition state stabilization. It is proposed that these observations are inconsistent with the conventional (Haldane) view of enzyme catalysis and are better reconciled with the shifting specificity model for enzyme catalysis.

One-pot four-component synthesis of thiazolidin-2-imines using Cu^I/Zn^II dual catalysis: A new class of acetylcholinesterase inhibitors

Shehzadi, Syeda Aaliya,Khan, Imtiaz,Saeed, Aamer,Larik, Fayaz Ali,Channar, Pervaiz Ali,Hassan, Mubashir,Raza, Hussain,Abbas, Qamar,Seo, Sung-Yum Academic Press 2019 Bioorganic chemistry Vol.84 No.-

<P><B>Abstract</B></P> <P>An efficient one-pot four-component strategy involving aldehydes, amines, alkynes and isothiocyanates has been developed to access a novel series of thiazolidine-2-imines (<B>5a-x</B>). This process operates under the action of a cooperative catalysis composed of Cu(I) and Zn(II) delivering the desired five-membered heterocyclic compounds in good to excellent yields. Notably, this transformation avoids the use of pre-formed imines or propargylamines and proceeds <I>via</I> an intramolecular 5-<I>exo-dig</I> hydrothiolation reaction of the <I>in situ</I> formed propargyl thiourea. Furthermore, the biological application of these motifs was demonstrated in terms of their strong acetylcholinesterase (AChE) inhibitory activity where compound <B>5s</B> was identified as the lead AChE inhibitor with an IC<SUB>50</SUB> value of 0.0023 ± 0.0002 μM, 88-folds stronger inhibition than standard drug (neostigmine methyl sulphate; IC<SUB>50</SUB> = 0.203 ± 0.004 μM). Molecular docking analysis reinforced the <I>in vitro</I> biological activity results revealing the formation of several useful interactions of the potent lead with amino acid residues in the active site of the enzyme.</P> <P><B>Highlights</B></P> <P> <UL> <LI> One-pot four component methodology was developed under Cu/Zn dual catalysis. </LI> <LI> A diverse range of thiazolidin-2-imines was prepared in excellent yields. </LI> <LI> Good functional group tolerance and broad substrate scope were explored. </LI> <LI> Potent inhibitors (<B>5b</B>, <B>5i</B>, <B>5s</B>, <B>5t</B>) of acetylcholinesterase were identified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Pd Nanoparticles Immobilized on Boehmite as an Efficient Heterogeneous Catalyst for Lubricant Hydrogenation

Asadi Zahra,Sadjadi Samahe,Bahri-Laleh Naeimeh,Nekoomanesh-Haghighi Mehdi 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.3

To furnish high-quality poly-alpha-olefi n oils, hydro-fi nishing under mild reaction conditions by a novel heterogeneous catalyst was accomplished. In this regard, Pd nanoparticles were immobilized on Boehmite. Then, the eff ect of hydrogenation variables, i.e., catalytic loading, reaction pressure, and temperature on the catalytic effi ciency, was investigated with response surface method. According to the results, a hydrogenation effi ciency of 85% was obtained at the optimum reaction conditions of T = 130 °C, P = 8 bar, and catalyst dosage = 5 wt%. Notably, the catalyst was recyclable for four runs with insignifi cant leaching of palladium nanoparticles. The comparison results suggested Pd/Boehmite catalyst as an appropriate alternative to the commercial Pd/Alumina and Pd/Silica. Hot fi ltration test also approved heterogeneous nature of catalysis.

Ni/SIRAL-30 as a heterogeneous catalyst for ethylene oligomerization

Lee, Maeum,Yoon, Ji Woong,Kim, Youngmin,Yoon, Ji Sun,Chae, Ho-Jeong,Han, Yo-Han,Hwang, Dong Won Elsevier 2018 Applied catalysis. A, General Vol.562 No.-

<P><B>Abstract</B></P> <P>The oligomerization of ethylene is an important catalytic process for the production of higher olefins, and is also a key step for jet-fuel production from bioethanol. We herein investigated the use of Ni/SIRAL-30 as a heterogeneous catalyst for ethylene oligomerization, as it can be prepared easily and cheaply by the simple impregnation of a Ni precursor on a commercial SIRAL-30 support with a high Brønsted acid site (BAS) density. Pyridine-infrared spectroscopy confirmed that proton species in the bridge-type Si-OH-Al frameworks of SIRAL-30 were partially exchanged with Ni<SUP>2+</SUP> cations without interfering with the Al<SUP>3+</SUP> sites. In addition, the Ni species following catalyst calcination under air and pretreatment with N<SUB>2</SUB> was identified to be the isolated Ni<SUP>2+</SUP> by XPS, EXAFS and CO adsorption. The Ni/SIRAL-30 catalyst gave almost complete ethylene conversion and stability over 100 h at 200 °C, 10 bar pressure, and at a weight hourly space velocity of 0.375 h<SUP>−1</SUP> during continuous ethylene oligomerization. A Ni loading of 4 wt% on SIRAL-30 was optimal for both ethylene conversion and for maximizing the proportion of C<SUB>10+</SUB> products formed, while the pretreatment of Ni(4 wt%)/SIRAL-30 at 550 °C under N<SUB>2</SUB> resulted in the best catalytic activity. Although a degree of deactivation was observed due to the adsorption of heavy oligomers, the initial catalytic activity was restored by heating the used catalyst at 550 °C under air. These results confirm that the Ni(4 wt%)/SIRAL-30 catalyst is both recyclable and an efficient heterogeneous catalyst for continuous ethylene oligomerization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni/SIRAL-30 was investigated as a heterogeneous catalyst for ethylene oligomerization. </LI> <LI> N<SUB>2</SUB> pretreatment of Ni/SIRAL-30 enhanced Ni<SUP>2+</SUP> dispersion and Brønsted acid site density. </LI> <LI> 4 wt% Ni loading on SIRAL-30 was optimal for both ethylene conversion and C<SUB>10+</SUB> products. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Photoelectrochemical Applications of Cyclometalated Ir(III) and Pt(II) Complexes

유영민 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Photoinduced redox chemistry serves as an extremely useful strategy to accessing thermodynamically challenging products. Metal complexes of period 6 transition metals, such as Ir and Pt, are promising for mediating the photoredox chemistries, because their excited states are longlived enough to permit highly efficient intermolecular electron exchange. We have been focused on the photoelectrochemical potentials of the cyclometalated complexes of Ir(III) and Pt(II) in a variety of organic transformations. Key advances include photoelectrocatalytic chromism of 1,2-dithienylethene compounds and trifluoromethylation of unactivated arenes and heterocycles. We believe that understanding of the photoelectrochemical functions of the complexes will enable the future development of novel catalysis.

Effect of HZSM-5 crystals for conversion of syngas to aromatics on Tandem catalysis: Balance between catalytic activity and stability

김남선,강윤,조창범,김용태 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.0