scholarly journals New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

2014 ◽  
Vol 10 ◽  
pp. 224-236 ◽  
Author(s):  
Helge Klare ◽  
Jörg M Neudörfl ◽  
Bernd Goldfuss
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
High Activity ◽  
Michael Addition ◽  
Bond Activation ◽  
High Catalytic Activity ◽  
Open Chain ◽  
High Hydrogen ◽  
Michael Additions ◽  
Asymmetric Michael Addition

Ten novel hydrogen-bonding catalysts based on open-chain PV-amides of BINOL and chinchona alkaloids as well as three catalysts based on rigid cis-PV-cyclodiphosphazane amides of N 1,N 1-dimethylcyclohexane-1,2-diamine have been developed. Employed in the asymmetric Michael addition of 2-hydroxynaphthoquinone to β-nitrostyrene, the open-chain 9-epi-aminochinchona-based phosphorus amides show a high catalytic activity with almost quantitative yields of up to 98% and enantiomeric excesses of up to 51%. The cyclodiphosphazane catalysts show the same high activity and give improved enantiomeric excesses of up to 75%, thus representing the first successful application of a cyclodiphosphazane in enantioselective organocatalysis. DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane PV-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by the catalyst.

scholarly journals Concerted Catalysis by Nanocellulose and Proline in Organocatalytic Michael Additions

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1231 ◽  
Author(s):  
Naliharifetra Ranaivoarimanana ◽  
Kyohei Kanomata ◽  
Takuya Kitaoka
Keyword(s):  
Catalytic Activity ◽  
Organic Synthesis ◽  
Michael Addition ◽  
Cellulose Nanofibers ◽  
Next Generation ◽  
Michael Additions ◽  
Asymmetric Michael Addition ◽  
First Time

Cellulose nanofibers (CNFs) have recently attracted much attention as catalysts in various reactions. Organocatalysts have emerged as sustainable alternatives to metal-based catalysts in green organic synthesis, with concerted systems containing CNFs that are expected to provide next-generation catalysis. Herein, for the first time, we report that a representative organocatalyst comprising an unexpected combination of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized CNFs and proline shows significantly enhanced catalytic activity in an asymmetric Michael addition.

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

ChemInform Abstract: Fast, Solvent-Free and Hydrogen-Bonding-Mediated Asymmetric Michael Addition in a Ball Mill.

ChemInform ◽  
2012 ◽  
Vol 43 (34) ◽  
pp. no-no
Author(s):  
Yi-Feng Wang ◽  
Ru-Xiang Chen ◽  
Ke Wang ◽  
Bin-Bin Zhang ◽  
Zhao-Bo Li ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Michael Addition ◽  
Ball Mill ◽  
Solvent Free ◽  
Asymmetric Michael Addition

Controllable synthesis of urchin-like hierarchical superstructure MOFs with high catalytic activity and stability

2021 ◽  
Author(s):  
Zhanke Wang ◽  
Lei Ge ◽  
Guangxu Zhang ◽  
Rongrong Gao ◽  
Hao Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Activity ◽  
Metal Organic Frameworks ◽  
High Catalytic Activity ◽  
Controllable Synthesis ◽  
Metal Organic ◽  
Self Assembled

A novel dissolution-crystallization strategy was developed to synthesize urchin-like superstructure metal-organic frameworks (MOFs) with self-assembled 1D nanorods. The superstructure MOFs not only inherit the high activity of nano-sized MOFs but...

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.

Novel ferrocene-based bifunctional amine–thioureas for asymmetric Michael addition of acetylacetone to nitroolefins

2015 ◽  
Vol 13 (17) ◽  
pp. 5054-5060 ◽  
Author(s):  
Xiaochen Ren ◽  
Chunyan He ◽  
Yingle Feng ◽  
Yonghai Chai ◽  
Wei Yao ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Efficient Method ◽  
Michael Addition ◽  
High Yield ◽  
Bifunctional Catalysts ◽  
Michael Adducts ◽  
Asymmetric Michael Addition ◽  
Multiple Hydrogen Bonding

An efficient method was developed to synthesize the ferrocene-based bifunctional amine–thioureas bearing multiple hydrogen-bonding donors. Asymmetric Michael addition of acetylacetone to nitroolefins catalyzed by these novel bifunctional catalysts affords the Michael adducts in high yield and moderate to excellent enantioselectivities.

PtRu Nanoparticle Catalytic Activity Enhanced by the Ligand Effect

2008 ◽  
Vol 1127 ◽  
Author(s):  
Shuji Goto ◽  
Yuli Li ◽  
Naomi Nagasawa ◽  
Tadashi Senoo ◽  
Kazuhiro Noda ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Fuel Cell ◽  
High Activity ◽  
Direct Methanol Fuel Cell ◽  
Metal Content ◽  
High Catalytic Activity ◽  
Ligand Effect ◽  
Direct Methanol ◽  
Methanol Fuel Cell ◽  
Ptru Nanoparticles

ABSTRACTWe synthesized a methanol electrocatalyst with high activity and low noble metal content. The electrocatalyst consists of carbon&supported PtRu nanoparticles, which have 1-2 Pt monoatomic layers on Ru nanocores. In spite of the pure Pt surface, the catalyst showed high catalytic activity when used in the anode of a direct methanol fuel cell. Clearly the underlying Ru atoms modified the property of the surface Pt atoms, bringing about the high catalytic activity.

scholarly journals Organocatalytic Asymmetric Michael Addition of Ketones to α, β-Unsaturated Nitro Compounds

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 618 ◽  
Author(s):  
Jae Ho Shim ◽  
Si Hun Nam ◽  
Byeong-Seon Kim ◽  
Deok-Chan Ha
Keyword(s):  
Michael Addition ◽  
Chemical Yield ◽  
Nitro Compounds ◽  
Neutral Condition ◽  
High Chemical ◽  
Aromatic Ketones ◽  
Michael Additions ◽  
Asymmetric Michael Addition ◽  
Neutral Conditions ◽  
Organic Catalyst

An organic catalyst “(R, R)-1,2-diphenylethylenediamine(DPEN) derivative’’ was devel-oped as a chiral bifunctional organocatalyst and applied for asymmetric Michael additions of aromatic ketones to trans-β-nitroalkene compounds under neutral conditions. The isopropyl-subs-tituted thiourea catalyst in neutral condition provides high chemical yield and enantioselectivities (ee) (up to 96% yield, 98% ee).

Fast, solvent-free and hydrogen-bonding-mediated asymmetric Michael addition in a ball mill

2012 ◽  
Vol 14 (4) ◽  
pp. 893 ◽  
Author(s):  
Yi-Feng Wang ◽  
Ru-Xiang Chen ◽  
Ke Wang ◽  
Bin-Bin Zhang ◽  
Zhao-Bo Li ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Michael Addition ◽  
Ball Mill ◽  
Solvent Free ◽  
Asymmetric Michael Addition
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