Sterically hindered benzoates: a synthetic strategy for modeling dioxygen activation at diiron active sites in proteinsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

2002 ◽  
pp. 653-660 ◽  
Author(s):  
William B. Tolman ◽  
Lawrence Que, Jr.
Keyword(s):  
Active Sites ◽  
Dioxygen Activation ◽  
Synthetic Strategy ◽  
Sterically Hindered

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

Dioxygen Activation at Mononuclear Nonheme Iron Active Sites:  Enzymes, Models, and Intermediates

2004 ◽  
Vol 104 (2) ◽  
pp. 939-986 ◽  
Author(s):  
Miquel Costas ◽  
Mark P. Mehn ◽  
Michael P. Jensen ◽  
Lawrence Que
Keyword(s):  
Active Sites ◽  
Nonheme Iron ◽  
Dioxygen Activation ◽  
Iron Active Sites

Dioxygen Activation at Mononuclear Nonheme Iron Active Sites: Enzymes, Models, and Intermediates

ChemInform ◽  
2004 ◽  
Vol 35 (21) ◽  
Author(s):  
Miquel Costas ◽  
Mark P. Mehn ◽  
Michael P. Jensen ◽  
Lawrence Jr. Que
Keyword(s):  
Active Sites ◽  
Nonheme Iron ◽  
Dioxygen Activation ◽  
Iron Active Sites

scholarly journals The Effect of Preparation Method of Ni-Supported SiO2 Catalysts for Carbon Dioxide Reforming of Methane

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1221
Author(s):  
Hua-Ping Ren ◽  
Si-Yi Ding ◽  
Qiang Ma ◽  
Wen-Qi Song ◽  
Yu-Zhen Zhao ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Active Sites ◽  
High Performance ◽  
Preparation Method ◽  
Complexing Agent ◽  
Preparation Process ◽  
Carbon Dioxide Reforming ◽  
Preparation Methods ◽  
Synthetic Strategy

Reforming methane to produce syngas is a subject that generates considerable interest. The process requires catalysts that possess high-performance active sites to activate stable C–H bonds. Herein, we report a facile synthetic strategy to prepare Ni-based catalysts by complexation–impregnation (Ni-G/SiO2-C) and precipitation–impregnation (Ni-G/SiO2-P) methods using glycine as a complexing agent. The particle size of Ni in both types of catalysts is decreased by adding glycine in the preparation process. Nevertheless, the preparation methods and amount of glycine play a significant role in the particle size and distribution of Ni over the Ni-based catalysts. The smaller particle size and narrower distribution of Ni were obtained in the Ni-G/SiO2-P catalyst. The catalysts were comparatively tested for carbon-dioxide reforming of methane (CDR). Ni-G/SiO2-P showed better CDR performance than Ni-G/SiO2-C and Ni/SiO2 and increased stability because of the smaller particle size and narrower distribution of Ni. Moreover, a high-performance Ni-based catalyst was prepared by optimizing the amount of glycine added. An unobservable deactivation was obtained over Ni-G-2/SiO2-P and Ni-G-3/SiO2-P for CDR during TOS = 20 h. Thus, a new promising method is described for the preparation of Ni-based catalysts for CDR.

Asymmetric Synthesis of Adamantyl GABA Analogues

Synthesis ◽  
2018 ◽  
Vol 51 (02) ◽  
pp. 463-469 ◽  
Author(s):  
Anastasiya Sibiryakova ◽  
Vadim Shiryaev ◽  
Alexander Reznikov ◽  
Anastasiya Kabanova ◽  
Yuri Klimochkin
Keyword(s):  
Asymmetric Synthesis ◽  
Michael Addition ◽  
Diethyl Malonate ◽  
Efficient Synthesis ◽  
Synthetic Strategy ◽  
Asymmetric Michael Addition ◽  
Gaba Analogues ◽  
Sterically Hindered

An efficient synthesis of (R)- and (S)-4-amino-3-(adamant-1-yl)butyric acids and (R)- and (S)-4-(adamant-1-yl)pyrrolidin-2-ones is presented. The synthetic strategy is based on asymmetric Michael addition of diethyl malonate to 1-(adamant-1-yl)-2-nitroethene using available Ni(II) complex as the catalyst. The procedures provide good to high enantioselectivity of Michael addition to sterically hindered nitroalkene and good yields of (R)- and (S)-enantiomers of 3-adamantyl substituted GABA.

A sterically hindered salen iron complex as a model for active sites of mononuclear non-heme iron enzymes

2003 ◽  
Vol 96 (1) ◽  
pp. 133 ◽  
Author(s):  
Hiroshi FuiJii ◽  
Takuya Kurahashi ◽  
Manabu Sugimoto ◽  
Kenji Oda ◽  
Takashi Ogura
Keyword(s):  
Active Sites ◽  
Iron Complex ◽  
Heme Iron ◽  
Non Heme Iron ◽  
Iron Enzymes ◽  
Sterically Hindered

scholarly journals WS2 moiré superlattices derived from mechanical flexibility for hydrogen evolution reaction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lingbin Xie ◽  
Longlu Wang ◽  
Weiwei Zhao ◽  
Shujuan Liu ◽  
Wei Huang ◽  
...  
Keyword(s):  
Active Sites ◽  
Hydrogen Adsorption ◽  
Theoretical Calculations ◽  
Catalytic Performance ◽  
Emergent Properties ◽  
Mechanical Instability ◽  
Synthetic Strategy ◽  
Exciting Opportunity ◽  
Catalytic Hydrogen ◽  
One Step

AbstractThe discovery of moiré superlattices (MSLs) opened an era in the research of ‘twistronics’. Engineering MSLs and realizing unique emergent properties are key challenges. Herein, we demonstrate an effective synthetic strategy to fabricate MSLs based on mechanical flexibility of WS2 nanobelts by a facile one-step hydrothermal method. Unlike previous MSLs typically created through stacking monolayers together with complicated method, WS2 MSLs reported here could be obtained directly during synthesis of nanobelts driven by the mechanical instability. Emergent properties are found including superior conductivity, special superaerophobicity and superhydrophilicity, and strongly enhanced electro-catalytic activity when we apply ‘twistronics’ to the field of catalytic hydrogen production. Theoretical calculations show that such excellent catalytic performance could be attributed to a closer to thermoneutral hydrogen adsorption free energy value of twisted bilayers active sites. Our findings provide an exciting opportunity to design advanced WS2 catalysts through moiré superlattice engineering based on mechanical flexibility.

scholarly journals Activity and Thermal Stability of Cobalt(II)-Based Olefin Polymerization Catalysts Adorned with Sterically Hindered Dibenzocycloheptyl Groups

Molecules ◽  
2019 ◽  
Vol 24 (10) ◽  
pp. 2007 ◽  
Author(s):  
Muhammad Zada ◽  
Liwei Guo ◽  
Yanping Ma ◽  
Wenjuan Zhang ◽  
Zygmunt Flisak ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Active Sites ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
Linear Polyethylene ◽  
Order Of Magnitude ◽  
Ft Ir ◽  
Sterically Hindered ◽  
Thermal Stability Of

Five examples of unsymmetrical 2-(2,4-bis(dibenzocycloheptyl)-6-methylphenyl- imino)ethyl)-6-(1-(arylyimino)ethyl)pyridine derivatives (aryl = 2,6-Me2C6H3 in L1; 2,6-Et2C6H3 in L2; 2,6-i-Pr2C6H3 in L3; 2,4,6-Me3C6H2 in L4 and 2,6-Et2-4-MeC6H2 in L5) were prepared and characterized. Treatment with CoCl2 offered the corresponding cobalt precatalysts Co1–Co5, which were characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The molecular structures of Co3 and Co4 determined by single crystal X-ray diffraction revealed distorted square pyramidal geometries with τ5 values of 0.052–0.215. Activated with either MAO or MMAO, the precatalysts displayed high activities in ethylene polymerization, where Co1 with the least bulky substituents exhibited a peak activity of 1.00 × 107 g PE mol−1 (Co) h−1 at 60 °C. With MAO as a cocatalyst, the activity was reduced only by one order of magnitude at 90 °C, which implies thermally stable active sites. The polymerization product was highly linear polyethylene with vinyl end groups. Co3 with the most sterically hindered active sites was capable of generating polyethylene of high molecular weight, reaching 6.46 × 105 g mol−1. Furthermore, high melting point and unimodal molecular weight distribution were observed in the resulting polyethylene. It must be stressed that the thermal stability of the catalyst and the molecular weight of the obtained polyethylene attain the highest values reported for the unsymmetrical 2,6-bis(imino)pyridylcobalt (II) chloride precatalysts.

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