Why electrostatically enhanced thiourea is better than Schreiner's thiourea in both catalytic activity and regioselectivity?

2019 ◽  
Vol 6 (11) ◽  
pp. 1821-1831 ◽  
Author(s):  
Chao-Xian Yan ◽  
Rui-Zhi Wu ◽  
Ka Lu ◽  
Fang-Ling Yang ◽  
Xiao-Shan Yang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Calculations ◽  
Ring Opening ◽  
Styrene Oxide ◽  
Better Than

Electrostatically enhanced thiourea is more active and efficient than Schreiner's thiourea in the ring-opening aminolysis of styrene oxide with aniline, and the underlying reasons were explored by DFT calculations.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

scholarly journals Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1651
Author(s):  
Felipe de la Cruz-Martínez ◽  
Marc Martínez de Sarasa Buchaca ◽  
Almudena del Campo-Balguerías ◽  
Juan Fernández-Baeza ◽  
Luis F. Sánchez-Barba ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Reaction Mechanism ◽  
Catalytic System ◽  
Phthalic Anhydride ◽  
Ring Opening ◽  
High Selectivity ◽  
Zinc Complexes ◽  
Cyclohexene Oxide ◽  
Reaction Conditions ◽  
Cyclic Anhydrides

The catalytic activity and high selectivity reported by bimetallic heteroscorpionate acetate zinc complexes in ring-opening copolymerization (ROCOP) reactions involving CO2 as substrate encouraged us to expand their use as catalysts for ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides. Among the catalysts tested for the ROCOP of CHO and phthalic anhydride at different reaction conditions, the most active catalytic system was the combination of complex 3 with bis(triphenylphosphine)iminium as cocatalyst in toluene at 80 °C. Once the optimal catalytic system was determined, the scope in terms of other cyclic anhydrides was broadened. The catalytic system was capable of copolymerizing selectively and efficiently CHO with phthalic, maleic, succinic and naphthalic anhydrides to afford the corresponding polyester materials. The polyesters obtained were characterized by spectroscopic, spectrometric, and calorimetric techniques. Finally, the reaction mechanism of the catalytic system was proposed based on stoichiometric reactions.

Organocalcium Compounds with Catalytic Activity for the Ring-Opening Polymerization of Lactones

2003 ◽  
Vol 2003 (18) ◽  
pp. 3432-3439 ◽  
Author(s):  
Matthias Westerhausen ◽  
Stefan Schneiderbauer ◽  
Alexander N. Kneifel ◽  
Yvonne Söltl ◽  
Peter Mayer ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ring Opening ◽  
Ring Opening Polymerization

scholarly journals p-Tolylimido rhenium(v) complexes – synthesis, X-ray studies, spectroscopic characterization, DFT calculations and catalytic activity

2014 ◽  
Vol 43 (6) ◽  
pp. 2596-2610 ◽  
Author(s):  
Barbara Machura ◽  
Izabela Gryca ◽  
Jan Grzegorz Małecki ◽  
Francisco Alonso ◽  
Yanina Moglie
Keyword(s):  
Catalytic Activity ◽  
Dft Calculations ◽  
Spectroscopic Characterization ◽  
X Ray

scholarly journals Use of pyrazoles as ligands greatly enhances the catalytic activity of titanium iso-propoxide for the ring-opening polymerization of l-lactide: a cooperation effect

RSC Advances ◽  
2020 ◽  
Vol 10 (67) ◽  
pp. 40690-40696
Author(s):  
Tzu-Fang Wang ◽  
Someswara Rao Kosuru ◽  
Shu-Chun Yu ◽  
Yung-Chi Chang ◽  
Hsin-Yu Lai ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
One Pot

Using TiOiPr4 with a pyrazole ligand for one-pot LA polymerization improved catalytic activity compared with using TiOiPr4 only.

scholarly journals Chiral MnIII (Salen) Immobilized on Organic Polymer/Inorganic Zirconium Hydrogen Phosphate Functionalized with 3-Aminopropyltrimethoxysilane as an Efficient and Recyclable Catalyst for Enantioselective Epoxidation of Styrene

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 212 ◽  
Author(s):  
Xiaochuan Zou ◽  
Yue Wang ◽  
Cun Wang ◽  
Kaiyun Shi ◽  
Yanrong Ren ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Supported Catalysts ◽  
Organic Polymer ◽  
Solid Catalyst ◽  
Homogeneous Catalyst ◽  
Hydrogen Phosphate ◽  
Characterization Methods ◽  
Salen Complexes ◽  
Enantioselective Epoxidation ◽  
Better Than

Organic polymers/inorganic zirconium hydrogen phosphate (ZSPP, ZPS-IPPA, and ZPS-PVPA) functionalized with 3-aminopropyltrimethoxysilane were prepared and used to support chiral MnIII (salen) complexes (Jacobsen’s catalyst). Different characterization methods demonstrated that the chiral MnIII (salen) complexes was successfully supported on the surface of the carrier (ZSPP, ZPS-IPPA, or ZPS-PVPA) through a 3-aminopropyltrimethoxysilane group spacer. The supported catalysts effectively catalyzed epoxidation of styrene with m-chloroperbenzoic acid (m-CPBA) as an oxidant in the presence of N-methylmorpholine N-oxide (NMO) as an axial base. These results (ee%, 53.3–63.9) were significantly better than those achieved under a homogeneous counterpart (ee%, 46.2). Moreover, it is obvious that there was no significant decrease in catalytic activity after the catalyst 3 was recycled four times (cons%: from 95.0 to 92.6; ee%: from 64.7 to 60.1). Further recycles of catalyst 3 resulted in poor conversions, although the enantioselectivity obtained was still higher than that of corresponding homogeneous catalyst even after eight times. After the end of the eighth reaction, the solid catalyst was allowed to stand in 2 mol/L of dilute hydrochloric acid overnight, prompting an unexpected discovery that the catalytic activity of the catalyst was recovered again at the 9th and 10th cycles of the catalyst.

scholarly journals Synergy between Ionic Liquids and CuCl2 in Gas–Liquid Phase Reactions of Acetylene Hydrochlorination

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 504 ◽  
Author(s):  
Yi Yu ◽  
Yuxue Yue ◽  
Bolin Wang ◽  
Haihua He ◽  
Zhong-Ting Hu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ionic Liquids ◽  
Activated Carbon ◽  
Liquid Phase ◽  
Dft Calculations ◽  
Synergetic Effect ◽  
Good Explanation ◽  
Experimental Results ◽  
Acetylene Hydrochlorination ◽  
Reaction Media

We studied the acetylene hydrochlorination in gas–liquid phase reactions using ionic liquids (IL) as the reaction media and CuCl2 as the catalyst. The Cu-IL catalyst showed strong synergy between the IL and the Cu(II) active catalytic species. For [PrMIm]Cl, the Cu-IL catalyst exhibited significant enhancement of the catalytic activity in comparison with the CuCl2 catalyst supported on activated carbon and the IL alone as the catalyst. We have also performed DFT calculations of the reaction process, which provides a good explanation of our experimental results and for the synergetic effect. Our result suggests that ILs may be used to improve the activity of other metallic catalysts for the hydrochlorination reaction of acetylene.

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