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  • 1.
    Bosque, Irene
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Magallanes, Gabriel
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Rigoulet, Mathilde
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Kärkäs, Markus D.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Redox Catalysis Facilitates Lignin Depolymerization2017In: ACS Central Science, ISSN 2374-7951, Vol. 3, no 6, p. 621-628Article in journal (Refereed)
    Abstract [en]

    Lignin is a recalcitrant and underexploited natural feedstock for aromatic commodity chemicals, and its degradation generally requires the use of high temperatures and harsh reaction conditions. Herein we present an ambient temperature one-pot process for the controlled oxidation and depolymerization of this potent resource. Harnessing the potential of electrocatalytic oxidation in conjugation with our photocatalytic cleavage methodology, we have developed an operationally simple procedure for selective fragmentation of β-O-4 bonds with excellent mass recovery, which provides a unique opportunity to expand the existing lignin usage from energy source to commodity chemicals and synthetic building block source.

  • 2.
    Iqbal, M. Naeem
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Abdel-Magied, Ahmed. F.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Abdelhamid, Hani Nasser
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Olsén, Peter
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Shatskiy, Andrey
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Zou, Xiaodong
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Åkermark, Björn
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Kärkäs, Markus D.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Johnston, Eric V.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Mesoporous Ruthenium Oxide: A Heterogeneous Catalyst for Water Oxidation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, p. 9651-9656Article in journal (Refereed)
    Abstract [en]

    Herein we report the synthesis of mesoporous ruthenium oxide (MP-RuO2) using a template-based approach. The catalytic efficiency of the prepared MP-RuO2 was compared to commercially available ruthenium oxide nanoparticles (C-RuO2) as heterogeneous catalysts for water oxidation. The results demonstrated superior performance of MP-RuO2 for oxygen evolution compared to the C-RuO2 with respect to recyclability, amount of generated oxygen, and stability over several catalytic runs.

  • 3.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Electrochemical strategies for C-H functionalization and C-N bond formation2018In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 47, no 15, p. 5786-5865Article, review/survey (Refereed)
    Abstract [en]

    Conventional methods for carrying out carbon-hydrogen functionalization and carbon-nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon-carbon and carbon-heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon-hydrogen functionalization and carbon-nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

  • 4.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Lignin Hydrogenolysis: Improving Lignin Disassembly through Formaldehyde Stabilization2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 10, p. 2111-2115Article, review/survey (Refereed)
    Abstract [en]

    Lignocellulosic biomass is available in large quantities and constitutes an attractive feedstock for the sustainable production of bulk and fine chemicals. Although methods have been established for the conversion of its cellulosic fractions, valorization of lignin has proven to be challenging. The difficulty in disassembling lignin originates from its heterogeneous structure and its propensity to undergo skeletal rearrangements and condensation reactions during biorefinery fractionation or biomass pretreatment processes. A strategy for hindering the generation of these resistive interunit linkages during biomass pretreatment has now been devised using formaldehyde as a stabilizing agent. The developed method when combined with Ru/C‐catalyzed hydrogenolysis allows for efficient disassembly of all three biomass fractions: (cellulose, hemicellulose, and lignin) and suggests that lignin upgrading can be integrated into prevailing biorefinery schemes.

  • 5.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, p. 4999-5022Article, review/survey (Refereed)
    Abstract [en]

    During the past decade, visible light photocatalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing visible light energy for synthetic purposes through the generation of reactive but controllable free radical species. Recent progress in the area of visible light photocatalysis has established it as an enabling catalytic strategy for the mild and selective generation of nitrogen-centered radicals. The application of visible light for photocatalytic activation of amides, hydrazones, and imides represents a valuable approach for facilitating the formation of nitrogen-centered radicals. Within the span of only a couple of years, significant progress has been made for expediting the generation of amidyl, hydrazonyl, and imidyl radicals from a variety of precursors. This Perspective highlights the recent advances in visible light-mediated generation of these radicals. A particular emphasis is placed on the unique ability of visible light photocatalysis in accessing elusive reaction manifolds for the construction of diversely functionalized nitrogen-containing motifs and as a platform for nontraditional bond disconnections in contemporary synthetic chemistry.

  • 6.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Bosque, Irene
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Magallanes, Gabriel
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Rigoulet, Mathilde
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Redox Catalysis Facilitates Lignin Depolymerization2017In: Synform, no 11, p. A189-A192Article, review/survey (Other academic)
    Abstract [en]

    The laboratory of Professor Corey Stephenson at the University of Michigan (Ann Arbor, USA) has had an interest in lignin depolymerization since 2014. According to Corey Stephenson there were two main reasons that initially attracted their attention towards lignin. On the one hand, there is its abundance and unique aromatic backbone, which makes it an exceptional renewable source for small aromatic chemicals. On the other hand there are only few examples of selective methodologies found in the literature regarding its depolymerization, a majority of them employing harsh conditions due to its recalcitrant nature. He added: “Since the major interest of my laboratory focuses on harnessing the energy of visible light, we saw the opportunity of using photoredox catalysis to selectively cleave the ß-O–4 bonds present in the lignin backbone, a methodology that proved to be exceptionally robust for lignin model systems.

    However, a prior oxidation step was required to achieve this fragmentation, which prompted us to search for alternative oxidation methodologies.” Such a method is presented in the present ACS Central Science publication.”

  • 7.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Bosque, Irene
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Photocatalytic Oxidation of Lignin Model Systems by Merging Visible-Light Photoredox and Palladium Catalysis2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 19, p. 5166-5169Article in journal (Refereed)
    Abstract [en]

    Lignin valorization has long been recognized as a sustainable solution for the renewable production of aromatic compounds. Two-step oxidation/reduction strategies, whereby the first oxidation step is required to “activate” lignin systems for controlled fragmentation reactions, have recently emerged as viable routes toward this goal. Herein we describe a catalytic protocol for oxidation of lignin model systems by combining photoredox and Pd catalysis. The developed dual catalytic protocol allowed the efficient oxidation of lignin model substrates at room temperature to afford the oxidized products in good to excellent yields.

  • 8.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Li, Ying-Ying
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Siegbahn, Per E. M.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Liao, Rong-Zhen
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Åkermark, Björn
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Metal-Ligand Cooperation in Single-Site Ruthenium Water Oxidation Catalysts: A Combined Experimental and Quantum Chemical Approach2018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 17, p. 10881-10895Article in journal (Refereed)
    Abstract [en]

    Catalysts for oxidation of water to molecular oxygen are essential in solar-driven water splitting. In order to develop more efficient catalysts for this oxidatively demanding reaction, it is vital to have mechanistic insight in order to understand how the catalysts operate. Herein, we report the mechanistic details associated with the two Ru catalysts 1 and 2. Insight into the mechanistic landscape of water oxidation catalyzed by the two single-site Ru catalysts was revealed by the use of a combination of experimental techniques and quantum chemical calculations. On the basis of the obtained results, detailed mechanisms for oxidation of water by complexes 1 and 2 are proposed. Although the two complexes are structurally related, two deviating mechanistic scenarios are proposed with metal-ligand cooperation being an important feature in both processes. The proposed mechanistic platforms provide insight for the activation of water or related small molecules through nontraditional and previously unexplored routes.

  • 9.
    Kärkäs, Markus D.
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Monos, Timothy M.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Magallanes, Gabriel
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Transition-Metal Catalyzed Valorization of Lignin: The Key to a Sustainable Carbon-Neutral Future2016In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 14, no 6, p. 1853-1914Article, review/survey (Refereed)
    Abstract [en]

    The development of a sustainable, carbon-neutral biorefinery has emerged as a prominent scientific and engineering goal of the 21st century. As petroleum has become less accessible, biomass-based carbon sources have been investigated for utility in fuel production and commodity chemical manufacturing. One underutilized biomaterial is lignin; however, its highly crosslinked and randomly polymerized composition have rendered this biopolymer recalcitrant to existing chemical processing. More recently, insight into lignin's molecular structure has reinvigorated chemists to develop catalytic methods for lignin depolymerization. This review examines the development of transition-metal catalyzed reactions and the insights shared between the homogeneous and heterogeneous catalytic systems towards the ultimate goal of valorizing lignin to produce value-added products.

  • 10.
    Kärkäs, Markus D.
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Enchained by Visible Light–Mediated Photoredox Catalysis2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 349, no 6254, p. 1285-1286Article in journal (Refereed)
    Abstract [en]

    Free radicals are exploited in biology, often through highly controlled enzymatic reactions, to drive many reactions that would be difficult via nonradical routes that transfer two electrons (1). In synthetic chemistry, visible-light photoredox catalysis has emerged as an economical and environmentally benign route for promoting free radical transformations in the lab (24). Although the initial light-sensitization steps are well established (5), insufficient attention has been dedicated to essential mechanistic features of the closed catalytic cycle (6). Several reports have hypothesized that these photocatalyzed reactions are terminated through a closed catalytic cycle, which delivers the final product and regenerates the ground state of the photosensitizer (PS). However, Cismesia and Yoon (6) highlight that some of the mechanistic proposals may be incomplete and may involve radical chains.

  • 11.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109, United States.
    Porco, John A. Jr
    Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis2016In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, no 17, p. 9683-9747Article, review/survey (Refereed)
    Abstract [en]

    The use of photochemical transformations is a powerful strategy that allows for the formation of a high degree of molecular complexity from relatively simple building blocks in a single step. A central feature of all light-promoted transformations is the involvement of electronically excited states, generated upon absorption of photons. This produces transient reactive intermediates and significantly alters the reactivity of a chemical compound. The input of energy provided by light thus offers a means to produce strained and unique target compounds that cannot be assembled using thermal protocols. This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds. Synthetic designs based on photochemical transformations have the potential to afford complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis.

  • 12.
    Liu, Jian Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Mat Sci, Xuzhou 221116, Jiangsu, Peoples R China.
    Chen, Xinyi
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Wang, Xiang-Shan
    Silver-Mediated Synthesis of Substituted Benzofuran- and Indole-Pyrroles via Sequential Reaction of ortho-Alkynylaromatics with Methylene Isocyanides2019In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 84, no 14, p. 8998-9006Article in journal (Refereed)
    Abstract [en]

    A silver-mediated reaction between 2-ethynyl-3-(1-hydroxyprop-2-yn-1-yl)phenols or 2-ethyn-yl-3-(1-hydroxy-prop-2-yn-1-yl)anilines and methylene isocyanides has been developed. A sequential 5-endo-dig cyclization and [3 + 2] cycloaddition process is proposed. This synthetic strategy is atom- and step-efficient and applicable to a broad scope of substrates, allowing the synthesis of valuable substituted benzofuran- and indole-pyrroles in moderate to high yields.

  • 13.
    Liu, Jian-Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. KTH Royal Inst Technol, Dept Chem, S-10044 Stockholm, Sweden..
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Matsuura, Bryan S.
    NYU, Dept Chem, New York, NY 10003 USA..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Recent Advances in Photoredox Catalysis Enabled Functionalization of alpha-Amino Acids and Peptides: Concepts, Strategies and Mechanisms2019In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, Vol. 51, no 14, p. 2759-2791Article, review/survey (Refereed)
    Abstract [en]

    The selective modification of alpha-amino acids and peptides constitutes a pivotal arena for accessing new peptide-based materials and therapeutics. In recent years, visible light photoredox catalysis has appeared as a powerful platform for the activation of small molecules via single-electron transfer events, allowing previously inaccessible reaction pathways to be explored. This review outlines the recent advances, mechanistic underpinnings, and opportunities of applying photoredox catalysis to the expansion of the synthetic repertoire for the modification of specific amino acid residues. 1 Introduction 2 Visible-Light-Mediated Functionalization of alpha-Amino Acids 2.1 Decarboxylative Functionalization Involving Redox-Active Esters 2.2 Direct Decarboxylative Coupling Strategies 2.3 Hypervalent Iodine Reagents 2.4 Dual Photoredox and Transition-Metal Catalysis 2.5 Amination and Deamination Strategies 3 Photoinduced Peptide Diversification 3.1 Gese-Type Bioconjugation Methods 3.2 Peptide Macrocyclization through Photoredox Catalysis 3.3 Biomolecule Conjugation through Arylation 3.4 C-H Functionalization Manifolds 4 Conclusions and Outlook

  • 14.
    Liu, Jian-Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China.
    Shen, Xuanyu
    Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China..
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhou, Enlong
    Shandong Agr Univ, Coll Chem & Mat Sci, Tai An 271000, Shandong, Peoples R China..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Wang, Xiang-Shan
    Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China..
    Silver-Induced [3+2] Cycloaddition of Isocyanides with Acyl Chlorides: Regioselective Synthesis of 2,5-Disubstituted Oxazoles2019In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899Article in journal (Refereed)
    Abstract [en]

    A silver-induced cycloaddition of isocyanides with acyl chlorides has been developed. This transition metal-catalyzed strategy provides an effective and scalable approach for the formation of 2,5-disubstituted oxazoles in good to high yields. The employed silver-based MOF catalyst can be efficiently recycled without compromising the yield.

  • 15.
    Magallanes, Gabriel
    et al.
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Bosque, Irene
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Lee, Sudarat
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Maldonado, Stephen
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA.;Univ Michigan, Program Appl Phys, Ann Arbor, MI 48109 USA..
    Stephenson, Corey R. J.
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Selective C-O Bond Cleavage of Lignin Systems and Polymers Enabled by Sequential Palladium-Catalyzed Aerobic Oxidation and Visible-Light Photoredox Catalysis2019In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 9, no 3, p. 2252-2260Article in journal (Refereed)
    Abstract [en]

    Lignin, which is a highly cross-linked and irregular biopolymer, is nature's most abundant source of aromatic compounds and constitutes an attractive renewable resource for the production of aromatic commodity chemicals. Herein, we demonstrate a practical and operationally simple two-step degradation approach involving Pd-catalyzed aerobic oxidation and visible-light photoredox-catalyzed reductive fragmentation for the chemoselective cleavage of the beta-O-4 linkage-the predominant linkage in lignin for the generation of lower-molecular-weight aromatic building blocks. The developed strategy affords the beta-O-4 bond cleaved products with high chemoselectivity and in high yields, is amenable to continuous flow processing, operates at ambient temperature and pressure, and is moisture- and oxygen-tolerant.

  • 16.
    Shatskiy, Andrey
    et al.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Bardin, Andrey A.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden.;Russian Acad Sci, Inst Problems Chem Phys, Academician Semenovs Prospect 1g, Moscow 142432, Russia..
    Oschmann, Michael
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Matheu, Roc
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Benet-Buchholz, Jordi
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Eriksson, Lars
    Stockholm Univ, Arrhenius Lab, Dept Mat & Environm Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Johnston, Eric, V
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden.;Sigrid Therapeut AB, Sankt Goransgatan 159, S-11217 Stockholm, Sweden..
    Gimbert-Surinach, Carolina
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Llobet, Antoni
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain.;Univ Autonoma Barcelona, Dept Quim, E-08193 Barcelona, Spain..
    Akermark, Bjorn
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Electrochemically Driven Water Oxidation by a Highly Active Ruthenium-Based Catalyst2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 10, p. 2251-2262Article in journal (Refereed)
    Abstract [en]

    The highly active ruthenium-based water oxidation catalyst [Ru-X(mcbp)(OHn)(py)(2)] [mcbp(2-)=2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine; n=2, 1, and 0 for X=II, III, and IV, respectively], can be generated in a mixture of Ru-III and Ru-IV states from either [Ru-II(mcbp)(py)(2)] or [Ru-III(Hmcbp)(py)(2)](2+) precursors. The precursor complexes are isolated and characterized by single-crystal X-ray analysis, NMR, UV/Vis, EPR, and FTIR spectroscopy, ESI-HRMS, and elemental analysis, and their redox properties are studied in detail by electrochemical and spectroscopic methods. Unlike the parent catalyst [Ru(tda) (py)(2)] (tda(2-)=[2,2:6,2-terpyridine]-6,6-dicarboxylate), for which full transformation into the catalytically active species [Ru-IV(tda)(O)(py)(2)] could not be carried out, stoichiometric generation of the catalytically active Ru-aqua complex [Ru-X(mcbp)(OHn)(py)(2)] from the Ru-II precursor was achieved under mild conditions (pH7.0) and short reaction times. The redox properties of the catalyst were studied and its activity for electrocatalytic water oxidation was evaluated, reaching a maximum turnover frequency (TOFmax) of around 40000s(-1) at pH9.0 (from foot-of-the-wave analysis), which is comparable to the activity of the state-of-the-art catalyst [Ru-IV(tda)(O)(py)(2)].

  • 17.
    Shatskiy, Andrey
    et al.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Åkermark, Björn
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden..
    The Art of Splitting Water: Storing Energy in a Readily Available and Convenient Form2019In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 15, p. 2020-2024Article in journal (Refereed)
    Abstract [en]

    This essay for EurJIC's special issue on "Redox Catalysis for Artificial Photosynthesis" introduces the reader to the field of water oxidation using molecular catalysts. The most essential challenge our society must address during the 21st century is perhaps the realization of a system for producing sustainable energy on the global scale. Currently, there exists an urgent need to develop effective and economical carbon-neutral or carbon-free energy technologies. The production of solar fuels through water splitting constitutes a key enabling element. The construction of robust and efficient catalysts for oxidation of water is therefore essential. In this essay the progress and mechanistic considerations pertaining to molecular water oxidation catalysts are described and discussed from a personal perspective.

  • 18.
    Shatskiy, Andrey
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Lundberg, Helena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Organic Electrosynthesis: Applications in Complex Molecule Synthesis2019In: ChemElectroChem, ISSN 2196-0216, Vol. 6, no 16, p. 4067-4092Article in journal (Refereed)
    Abstract [en]

    Organic electrosynthesis is an enabling and sustainable technology, which constitutes a rapidly expanding field of research. Electrochemical approaches serve as convenient and green alternatives to stoichiometric and toxic chemical redox agents. Electrosynthesis constitutes a promising platform for harnessing the unique reactivity profiles of radical intermediates, expediting the development of new reaction manifolds. This Review highlights both anodic and cathodic methods for the construction of various kinds of complex molecules.

1 - 18 of 18
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