Mechanistic studies of base-catalysed lignin depolymerisation in dimethyl carbonate

2018 ◽  
Vol 20 (1) ◽  
pp. 170-182 ◽  
Author(s):  
Saumya Dabral ◽  
Julien Engel ◽  
Jakob Mottweiler ◽  
Stephanie S. M. Spoehrle ◽  
Ciaran W. Lahive ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Lignin Degradation ◽  
Dimethyl Carbonate ◽  
Analytical Techniques ◽  
Mechanistic Studies

Various analytical techniques and DFT calculations have been applied in studying base-catalysed lignin degradation in dimethyl carbonate.

scholarly journals C-H Functionalization Reactions of Unprotected N-Heterocycles by Gold Catalyzed Carbene Transfer

2020 ◽  
Author(s):  
Sripati Jana ◽  
Claire Empel ◽  
Chao Pei ◽  
Polina Aseeva ◽  
Thanh Vinh Nguyen ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Functional Groups ◽  
Gold Catalyst ◽  
Protecting Groups ◽  
Transfer Reactions ◽  
Mechanistic Studies ◽  
Economic Strategies ◽  
Carbene Transfer ◽  
Functionalization Reaction

<p>The C-H functionalization reaction of N-heterocycles with unprotected N-H group is one of the most step-economic strategies to introduce functional groups without the need of installation and removal of protecting groups. Despite recent significant advances in C-H functionalization chemistry, this strategy remains unsatisfactorily developed. In this report, we disclose a simple and straightforward protocol to allow for the selective C-H functionalization of unprotected double benzannellated N-heterocycles via gold catalyzed carbene transfer reactions (29 examples, up to 86% yield). The scope of the reaction can also be expanded to the corresponding protected heterocycles (37 examples, up to 98% yield), further demonstrating the generality of this method. Mechanistic studies by DFT calculations underpin the importance of the gold catalyst and reveal that the selectivity of this reaction is driven by trace amounts of water present in the reaction mixture.</p>

Activation of Molecular Hydrogen over a Binuclear Complex with Rh2S2Core:  DFT Calculations and NMR Mechanistic Studies

2004 ◽  
Vol 126 (38) ◽  
pp. 11954-11965 ◽  
Author(s):  
Andrea Ienco ◽  
Maria José Calhorda ◽  
Joachim Reinhold ◽  
Francesca Reineri ◽  
Claudio Bianchini ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Molecular Hydrogen ◽  
Binuclear Complex ◽  
Mechanistic Studies

Frontiers of water oxidation: the quest for true catalysts

2017 ◽  
Vol 46 (20) ◽  
pp. 6124-6147 ◽  
Author(s):  
J. Li ◽  
R. Güttinger ◽  
R. Moré ◽  
F. Song ◽  
W. Wan ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Analytical Techniques ◽  
Mechanistic Studies ◽  
Oxidation Catalysts

Development of advanced analytical techniques is essential for the identification of water oxidation catalysts together with mechanistic studies.

scholarly journals Manganese-Catalyzed Ammonia Oxidation into Dinitrogen

2020 ◽  
Author(s):  
Hiroki Toda ◽  
Kazunari Nakajima ◽  
Ken Sakata ◽  
Yoshiaki Nishibayashi
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Ammonia Oxidation ◽  
Nucleophilic Attack ◽  
Mechanistic Studies ◽  
Oxidative Conversion ◽  
Functional Theory ◽  
Metal Catalyzed ◽  
Nitrogen Bond

Base metal-catalyzed oxidative conversion of ammonia into dinitrogen is a promising process to utilize ammonia as an energy carrier. In this study, we report the manganese-catalyzed ammonia oxidation under chemical and electrochemical conditions. Mechanistic studies including density functional theory (DFT) calculations suggest that a nucleophilic attack of ammonia on manganese nitrogenous complexes occurs to form a nitrogen–nitrogen bond leading to dinitrogen.<br>

scholarly journals Bimetallic Cooperativity with a 2-Phosphinoimidazole-Derived Pd(II) Dimer Enables Naphthalene Synthesis via dimeric Pd(III) Catalysis

2020 ◽  
Author(s):  
Chloe C. Ence ◽  
S. Hadi Nazari ◽  
Mariur Rodriguez Moreno ◽  
Manase F. Matu ◽  
Samantha G. Kulka ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Calculations ◽  
Oxidation State ◽  
Methyl Ketone ◽  
Methyl Ketones ◽  
Mechanistic Studies ◽  
High Oxidation State ◽  
Pd Catalysts ◽  
Silver Triflate ◽  
High Oxidation

We report the synthesis of bimetallic Pd(I) and Pd(II) complexes scaffolded on bidentate 2-phosphinoimidazole ligands. These complexes display unique catalytic activity and enable the expeditious formation of 1,3-disubstituted naphthalenes via an unprecedented coupling of aryl iodides and methyl ketones in the presence of silver triflate. Excellent substrate scope for naphthalene formation is also demonstrated. Mechanistic studies suggest that the transformation proceeds via Pd-catalyzed arylation of a methyl ketone, followed by cyclization with a second equivalent of ketone. Importantly, this ketone arylation processes occurs under oxidizing conditions, suggesting involvement of higher oxidation state dimeric Pd catalysts. Based on experiments and DFT calculations, we propose a mechanism involving high oxidation state Pd(III) bimetallic catalysis. These new bimetallic complexes possess reactivity that is not seen with monometallic Pd catalysts and we confirm the importance of the palladium catalyst for both arylation and cyclization for naphthalene formation.

scholarly journals Ligand-Controlled Regiodivergence in Nickel-Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids

2020 ◽  
Author(s):  
Zi-Qi Li ◽  
Yue Fu ◽  
Ruohan Deng ◽  
Van Tran ◽  
Yang Gao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Transition State ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Steric Effects ◽  
High Yield ◽  
Mechanistic Studies ◽  
Ligand Environment ◽  
Ligand Free ◽  
Electronic And Steric Effects

<div>A nickel-catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99% yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate- and regioselectivity-determining transmetalation transition state. <br></div>

scholarly journals Ligand-Controlled Regiodivergence in Nickel-Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids

2020 ◽  
Author(s):  
Zi-Qi Li ◽  
Yue Fu ◽  
Ruohan Deng ◽  
Van Tran ◽  
Yang Gao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Transition State ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Steric Effects ◽  
High Yield ◽  
Mechanistic Studies ◽  
Ligand Environment ◽  
Ligand Free ◽  
Electronic And Steric Effects

<div>A nickel-catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99% yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate- and regioselectivity-determining transmetalation transition state. <br></div>

scholarly journals Manganese-Catalyzed Ammonia Oxidation into Dinitrogen

2020 ◽  
Author(s):  
Hiroki Toda ◽  
Kazunari Nakajima ◽  
Ken Sakata ◽  
Yoshiaki Nishibayashi
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Ammonia Oxidation ◽  
Nucleophilic Attack ◽  
Mechanistic Studies ◽  
Oxidative Conversion ◽  
Functional Theory ◽  
Metal Catalyzed ◽  
Nitrogen Bond

Base metal-catalyzed oxidative conversion of ammonia into dinitrogen is a promising process to utilize ammonia as an energy carrier. In this study, we report the manganese-catalyzed ammonia oxidation under chemical and electrochemical conditions. Mechanistic studies including density functional theory (DFT) calculations suggest that a nucleophilic attack of ammonia on manganese nitrogenous complexes occurs to form a nitrogen–nitrogen bond leading to dinitrogen.<br>

scholarly journals Mechanistic Studies of Pd(II)-Catalyzed E/Z Isomerization of Unactivated Alkenes: Evidence for a Monometallic Nucleopalladation Pathway

2020 ◽  
Author(s):  
Rei Matsuura ◽  
Malkanthi Karunananda ◽  
Mingyu Liu ◽  
Nhi Nguyen ◽  
Donna Blackmond ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Kinetic Analysis ◽  
Kinetic Modeling ◽  
Spectroscopic Studies ◽  
Mechanistic Studies ◽  
Common Process ◽  
Directing Group

Pd(II)-catalyzed <i>E</i>/<i>Z</i> isomerization of alkenes is a common process—yet is largely uncharacterized, particularly with non-conjugated alkenes. In this work, the mechanism of Pd(II)-catalyzed <i>E</i>/<i>Z</i> isomerization of unactivated olefins containing an aminoquinoline-based amide directing group is probed using <i>in situ</i> kinetic analysis, spectroscopic studies, kinetic modeling, and DFT calculations. The directing group allows for stabilization and monitoring of previously undetectable intermediates. Collectively, the data are consistent with isomerization occurring through a monometallic nucleopalladation mechanism.

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