scholarly journals Allosteric Regulation of Supramolecular Oligomerization and Catalytic Activity via Coordination-Based Control of Competitive Hydrogen-Bonding Events

2014 ◽  
Vol 136 (47) ◽  
pp. 16594-16601 ◽  
Author(s):  
C. Michael McGuirk ◽  
Jose Mendez-Arroyo ◽  
Alejo M. Lifschitz ◽  
Chad A. Mirkin
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Allosteric Regulation

Synthesis of 1,2-Diamine Bifunctional Catalysts for the Direct Aldol Reaction Through Probing the Remote Amide Hydrogen

2019 ◽  
Vol 6 (2) ◽  
pp. 171-176
Author(s):  
Rajasekhar Dodda ◽  
Sampak Samanta ◽  
Matthew Su ◽  
John Cong-Gui Zhao
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Aldol Reaction ◽  
Catalytic Efficiency ◽  
Aldol Reactions ◽  
Catalyst Loading ◽  
Bifunctional Catalysts ◽  
Amide Hydrogen ◽  
Highly Efficient ◽  
Direct Aldol Reaction

Background: While proline can catalyze the asymmetric direct aldol reactions, its catalytic activity and catalyst turnover are both low. To improve the catalytic efficiency, many prolinebased organocatalysts have been developed. In this regard, prolinamide-based bifunctional catalysts have been demonstrated by us and others to be highly efficient catalysts for the direct aldol reactions. Results: Using the β-acetamido- and β-tosylamidoprolinamide catalysts, the highly enantio- and diastereoselective direct aldol reactions between enolizable ketones and aldehydes were achieved (up to >99% ee, 98:2 dr). A low catalyst loading of only 2-5 mol % of the β-tosylamidoprolinamide catalyst was needed to obtain the desired aldol products in good to high yields and high stereoselectivities. Methods: By carefully adjusting the hydrogen bonding ability of the remote β-amide hydrogen of the 1,2-diamine-based prolinamide bifunctional catalysts, the catalytic activity and the asymmetric induction of these catalysts were significantly improved for the direct aldol reaction between aldehydes and enolizable ketones. Conclusion: Some highly efficient 1,2-diamine-based bifunctional prolinamide catalysts have been developed through probing the remote β-amide hydrogen for its hydrogen bonding capability. These catalysts are easy to synthesize and high enantioselectivities may be achieved at very low catalyst loadings.

Effects of methoxy-substituted metalloporphyrins in catalytic alkene epoxidation by n-Bu4NHSO5

2010 ◽  
Vol 14 (04) ◽  
pp. 335-342 ◽  
Author(s):  
Amineh Aghabali ◽  
Nasser Safari
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
High Activity ◽  
Solvent Mixture ◽  
Steric Effects ◽  
Reaction Condition ◽  
Reaction Solution ◽  
Phenyl Rings ◽  
Active Intermediate ◽  
The Stability

TPPMnOAc and four different kinds of manganese tetraphenylporphyrin acetates were synthesized using different numbers of methoxy substituents in various positions of the phenyl rings. These porphyrins were used as catalysts in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5) as the oxidant and imidazole as the axial base. The following order of catalytic activity was obtained: TPPMnOAc ≥ T (2,3- OMeP ) PMnOAc > T (4- OMeP ) PMnOAc > T (3,4- OMeP ) PMnOAc > T (2,4,6- OMeP ) PMnOAc . By studying the UV-vis spectra in the reaction solution, the stability of the applied methoxy porphyrins and the effect of this factor on obtained yields were investigated. Lower catalytic activity in some of the methoxy porphyrins emphasized steric effects and special hydrogen bonding among the reaction elements. However, the stability of T (2,3- OMeP ) PMnOAc under our reaction condition was considerable and high activity was observed. By adding small amounts of alcohol to the reaction solution, the effect of the solvent mixture was previewed and steps were taken to identify the active intermediate of the catalyst in these conditions.

Understanding the role of hydrogen bonding in Brønsted acidic ionic liquid-catalyzed transesterification: a combined theoretical and experimental investigation

2016 ◽  
Vol 18 (48) ◽  
pp. 32723-32734 ◽  
Author(s):  
Kaixin Li ◽  
Yibo Yan ◽  
Jun Zhao ◽  
Junxi Lei ◽  
Xinli Jia ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Ionic Liquid ◽  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Ionic Liquids ◽  
Acidic Ionic Liquid ◽  
Brønsted Acidic Ionic Liquid ◽  
Acidic Ionic Liquids ◽  
Hydrogen Bonding Networks

The intra- and inter-hydrogen bonding networks that govern the catalytic activity of Brønsted acidic ionic liquids were identified.

Effect of hydrogen bonding on catalytic activity of some manganese porphyrins in epoxidation reactions

2011 ◽  
Vol 15 (03) ◽  
pp. 181-187 ◽  
Author(s):  
Tahereh Alemohammad ◽  
Nasser Safari ◽  
Samira Osati
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Axial Ligand ◽  
Hydroxyl Groups ◽  
Manganese Porphyrins ◽  
Bonding Effect ◽  
Meso Position ◽  
Hydrogen Bonding Effect ◽  
Mn Porphyrins ◽  
Effective Hydrogen

Mn (III)-tetra phenyl porphyrin-acetate (MnTPPOAc) and some kinds of meso-phenyl substituted porphyrins by hydroxyl groups and their Mn (III) complexes were synthesized. These Mn -porphyrins were used as catalyst in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n- Bu4NHSO5 ) as oxidant and tetra-n-butylammonium acetate (n- Bu4NOAc ) as the axial ligand. The following order of catalytic activity was observed for cyclooctene: T(2,3-OHP)PMnOAc ≫ T(2,4,6-OHP)PMnOAc ≥ T(4-OHP)PMnOAc ≥ T(2,6-OHP)PMnOAc ≥ TPPMnOAc and T(2,3-OHP)PMnOAc ≫ TPPMnOAc > T(4-OHP)PMnOAc > T(2,4,6-OHP)PMnOAc > T(2,6-OHP)PMnOAc for other alkenes. Different activity and stability of the catalysts were interpreted based on the hydrogen bonding between hydroxyl groups with appropriate orientation on the meso-position of the phenyl groups and axial bases or oxidant. T(2,3-OHP)PMnOAc catalyst has shown optimal condition for effective hydrogen bonding. In the case of other catalysts, electronic and steric factors overcome the hydrogen bonding effect.

scholarly journals Substrate-dependent allosteric regulation by switchable catalytic molecular tweezers

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Lorien Benda ◽  
Benjamin Doistau ◽  
Caroline Rossi-Gendron ◽  
Lise-Marie Chamoreau ◽  
Bernold Hasenknopf ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Closed Form ◽  
Binding Site ◽  
Lewis Acid ◽  
Metal Ion ◽  
Biological Systems ◽  
Allosteric Regulation ◽  
Experimental Results ◽  
Enzymatic Reactions ◽  
Molecular Tweezers

AbstractAllosteric regulation is exploited by biological systems to regulate the activity and/or selectivity of enzymatic reactions but remains a challenge for artificial catalysts. Here we report switchable terpy(Zn-salphen)2 molecular tweezers and their metal-dependent allosteric regulation of the acetylation of pyridinemethanol isomers. Zinc-salphen moieties can both act as a Lewis acid to activate the anhydride reagents and provide a binding site for pyridinemethanol substrates. The tweezers’ conformation can be reversibly switched between an open and a closed form by a metal ion stimulus. Both states offer distinct catalytic profiles, with closed tweezers showing superior catalytic activity towards ortho substrates, while open tweezers presenting higher rate for the acetylation of meta and para substrates. This notable substrate dependent allosteric response is rationalized by a combination of experimental results and calculations supporting a bimetallic reaction in the closed form for ortho substrate and an inhibition of the cavity for meta and para substrates.

A comprehensive density functional theory study of the key role of fluorination and dual hydrogen bonding in the activation of the epoxide/CO2 coupling by fluorinated alcohols

RSC Advances ◽  
2016 ◽  
Vol 6 (43) ◽  
pp. 36327-36335 ◽  
Author(s):  
M. Alves ◽  
R. Mereau ◽  
B. Grignard ◽  
C. Detrembleur ◽  
C. Jerome ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Density Functional ◽  
Ammonium Bromide ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Fluorinated Alcohols ◽  
Fluorinated Alcohol

DFT calculations allow understanding the key role of fluorination and dual hydrogen bonding responsible for the remarkable catalytic activity of the fluorinated alcohol/ammonium bromide bicomponent organocatalysts for the epoxide/CO2 coupling.

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