Article
Chemistry, Multidisciplinary
Parul Garg, Tavinder Singh, Anand Singh
Summary: This study describes the photochemical functionalization of alkoxyoxazoles with trimethylsilyl azide and N,N-dimethylanilines. These C-N bond forming reactions proceed with the assistance of organic dyes as photocatalyst and molecular oxygen, leading to oxidative ring-opening and access to novel chemical space. The unusual demethylative C-N bond formation in the case of N,N-dimethylanilines establishes a new reactivity pattern for these precursors.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Xukai Zhou, Daniel Pyle, Zining Zhang, Guangbin Dong
Summary: Here we present the development of a deacylative thiolation reaction for diverse methyl ketones. This reaction is redox-neutral and heavy-metal-free, providing a novel approach for site-specific introduction of thioether groups at unactivated aliphatic positions. It exhibits excellent functional group tolerance and wide substrate scope, enabling late-stage derivatization. The reaction relies on efficient condensation between the activation reagent and ketone substrates, leading to aromatization-driven C-C fragmentation and rapid radical coupling with thiosulfonates. Experimental and computational mechanistic studies suggest a radical chain pathway.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Review
Green & Sustainable Science & Technology
Huan Chen, Kun Wan, Fangjuan Zheng, Zhuo Zhang, Yayun Zhang, Donghui Long
Summary: Depletion of traditional fossil fuel reserves and environmental issues have spurred the exploration of renewable resources, with lignin being an underestimated source with potential to replace fossil fuels. Photocatalysis offers a promising platform for versatile lignin transformation, though challenges remain in fully unlocking its potential.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2021)
Article
Chemistry, Multidisciplinary
Mo Zhang, Zheng Li, Yeqin Feng, Xing Xin, Guo-Yu Yang, Hongjin Lv
Summary: Selective photocatalytic hydrogenolysis of lignin beta-O-4 models was achieved using Ni-containing polyoxometalate (POM) catalysts and CdS quantum dots under blue LED light irradiation. The system demonstrated high conversion and selectivity in transforming lignin beta-O-4 models to phenols and ketones. A potential photocatalytic mechanism was proposed based on experimental and spectroscopic analyses. This facile strategy has the potential for the photocatalytic production of various value-added chemicals from natural or biomass derivatives.
Article
Multidisciplinary Sciences
Mingyang Liu, Paul J. Dyson
Summary: Efficient valorization of lignin, a sustainable and renewable source, is essential for reducing dependence on fossil-derived feedstocks. This study presents a highly efficient strategy for extracting aromatic monomers and generating functionalized diaryl ethers from lignin using oxidative cross-coupling reactions.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Yaxuan Jing, Mohsen Shakouri, Xiaohui Liu, Yongfeng Hu, Yong Guo, Yanqin Wang
Summary: Researchers have developed a strategy to selectively cleave C-C bonds in aromatic plastics using catalyst Ru/Nb2O5 through methanol poisoning, resulting in monocyclic phenolic compounds.
Article
Chemistry, Multidisciplinary
Yoshiyuki Uruma, Tomohiro Yamada, Tsubasa Kojima, Tianyuan Zhang, Chen Qu, Moe Ishihara, Takashi Watanabe, Kan Wakamatsu, Hirofumi Maekawa
Summary: In this study, the degradation of three lignin model compounds was investigated using organic electrolysis. The results suggest that the organic electrolytic reaction can be used for the degradation reaction of a lignin model with b-O-4 bonds.
Article
Chemistry, Multidisciplinary
Meng Zhang, Bei-Bei Zhang, Qijie Lin, Ziling Jiang, Jianqi Zhang, Yawen Li, Shurui Pei, Xiao Han, Haigen Xiong, Xinyu Liang, Yuze Lin, Zhixiang Wei, Fengjiao Zhang, Xin Zhang, Zhi-Xiang Wang, Qinqin Shi, Hui Huang
Summary: An efficient Pd and Cu co-catalyzed direct arylation polycondensation was developed via inert C-S bond cleavage of aryl thioethers. This method showed high robustness and selectivity in synthesizing high performance conjugated polymers.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Miao Wang, Jinglan Wen, Yahao Huang, Peng Hu
Summary: An efficient method has been developed for selective degradation of styrene-related plastics under gentle conditions through multiple oxidation, catalyzed with inexpensive iron salts under visible light using oxygen as a green oxidant. Furthermore, simple iron salts could be used as additives for degradable plastics.
Article
Chemistry, Organic
Sang Mi Suh, Subramanian Jambu, Mason T. Chin, Tianning Diao
Summary: Selective depolymerization of lignin is a significant challenge in biomass conversion. This study proposes a strategy for lignin degradation by utilizing photoredox deoxygenative radical formation to trigger reverse biosynthesis, cleaving model compounds of beta-O-4 and beta-5-beta-O-4 linkages to produce monolignols.
Article
Engineering, Environmental
Jun Deng, Chi Zhou, Yue Yang, Bing Nan, Lin Dong, Lingchao Cai, Lina Li, Zhu-Jun Wang, Xiaofei Yang, Zupeng Chen
Summary: A mesoporous carbon nitride-supported ruthenium single-atom photocatalyst was developed for the selective cleavage of lignin C-C bonds. The catalyst exhibited high activity and selectivity under visible-light irradiation and room temperature. This work explores the potential of single-atom catalysts for the photocatalytic production of aromatics from renewable biomass feedstocks.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Youwei Xu, Shanmeng Lin, Rongkun He, Yichuan Zhang, Quan Gao, Dennis K. P. Ng, Jin Geng
Summary: The research presents a photoactivation system that cleaves unsaturated bonds using visible light, allowing for the release of aldehydes in live cells. It also demonstrates the targeting of specific cells using a mannose-functionalized photocage.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Chemistry, Organic
Hui Chen, Ranran Cui, Yahui Zhang, Yu Gao, Haijun Chen
Summary: In this study, a mild and metal-free synthesis of 3,3'-bisindoles is reported. The synthesis involves removal of the Fmoc group and subsequent cleavage of C-C and C-N bonds to generate the desired product. The resulting scaffold is suitable for further functionalization and exhibits interesting photophysical properties in both solution and solid state, suggesting its potential application in organic luminophores.
ORGANIC CHEMISTRY FRONTIERS
(2022)
Article
Chemistry, Multidisciplinary
Xing Xin, Zheng Li, Manzhou Chi, Mo Zhang, Yuanyuan Dong, Hongjin Lv, Guo-Yu Yang
Summary: Efficient and selective cleavage of beta-O-4 linkage under mild conditions is a promising strategy for converting lignocellulose to value-added aromatic chemicals. This study successfully constructed a recoverable polyoxometalate-ionic liquid (POM-IL) catalyst by reacting H5PMo10V2O40 polyoxoacids with 1-methyl-3-(4-sulfobutyl)-1H-imidazolium zwitterions. The POM-IL catalyst can selectively and effectively convert various beta-O-4 lignin models into aromatic acids and phenols under mild homogeneous conditions, and can be easily recovered for multiple recycling tests.
Article
Chemistry, Multidisciplinary
Shihao Su, Ling-Ping Xiao, Xue Chen, Shuizhong Wang, Xiao-Hong Chen, Yanzhu Guo, Shang-Ru Zhai
Summary: Ru/CNT catalyst exhibits high selectivity and yield towards lignin hydrogenolysis. The yields of aromatic monomers are related to lignin sources and decrease in the order: hardwoods > herbaceous plants > softwoods. The scission of C-O bonds and the high selectivity to monomeric aromatic compounds over the Ru/CNT catalyst are enhanced by avoiding side condensation. The fabricated Ru/CNT shows good reusability and recyclability, applicability, and biomass feedstock compatibility.
Review
Chemistry, Multidisciplinary
Philip R. D. Murray, James H. Cox, Nicholas D. Chiappini, Casey B. Roos, Elizabeth A. McLoughlin, Benjamin G. Hejna, Suong T. Nguyen, Hunter H. Ripberger, Jacob M. Ganley, Elaine Tsui, Nick Y. Shin, Brian Koronkiewicz, Guanqi Qiu, Robert R. Knowles
Summary: This article presents a comprehensive review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCET involves the simultaneous exchange of an electron and a proton in a non-classical redox mechanism, offering opportunities for the direct generation of synthetically useful free radical intermediates from common organic functional groups. The article provides an introduction to MS-PCET and a practitioner's guide to reaction design, focusing on the unique energetic and selectivity features of this reaction class. It also discusses various oxidative and reductive PCET activations for bond homolysis and the applications of MS-PCET in asymmetric catalysis, materials, and device applications.
Article
Chemistry, Multidisciplinary
Kuo Zhao, Robert R. Knowles
Summary: A novel light-driven method for the contra-thermodynamic positional isomerization of olefins is described, involving stepwise PCET activation and in situ protodemetalation steps to achieve regioselective and efficient transformation of olefin substrates. The method demonstrated good compatibility with a broad range of isopropylidene substrates and presents promising prospects for further mechanistic investigations.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
J. D. Earley, A. Zieleniewska, H. H. Ripberger, N. Y. Shin, M. S. Lazorski, Z. J. Mast, H. J. Sayre, J. K. McCusker, G. D. Scholes, R. R. Knowles, O. G. Reid, G. Rumbles
Summary: Cyclometalated and polypyridyl complexes of d(6) metals have great potential as photoredox catalysts, and besides the known criteria for modifying activity, such as tuning redox potentials, absorption energy, excited-state lifetime, and quantum yield, ion pair reorganization may also be an important factor in controlling reactivity.
Article
Chemistry, Multidisciplinary
Scott W. Spring, Chloe S. Cerione, Jesse H. Hsu, Shelby L. Shankel, Brett P. Fors
Summary: By synthesizing a solid, colorless chain-transfer agent (CTA), we have achieved efficient polymerization with excellent control over molecular weight, low dispersity values, high chain end fidelity, and temporal control in cationic RAFT polymerizations. The CTA was produced through a green synthetic route and showed utility in chemical, electrochemical, photochemical, and acid-initiated methods.
CHINESE JOURNAL OF CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Eve Y. Xu, Jacob Werth, Casey B. Roos, Andrew J. Bendelsmith, Matthew S. Sigman, Robert R. Knowles
Summary: Noncovalent interactions play a crucial role in molecular recognition in various chemical reactions. This study investigates the structures and properties of noncovalent interactions involving free radical intermediates, focusing on the enantioselective radical hydroamination of alkenes with sulfonamides. The results demonstrate the importance of attractive noncovalent interactions between a neutral sulfonamidyl radical intermediate and a chiral phosphoric acid in achieving asymmetric induction. Computational and data science-based evidence further elucidate the specific radical noncovalent interactions that contribute to the enantioselectivity.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Suhong Kim, Pan-Pan Chen, K. N. Houk, Robert R. Knowles
Summary: This study presents a case of catalytic carbon-carbon sigma-bond homolysis achieved through coordination-induced bond-weakening effect, with a ruthenium redox couple used for bond weakening. Experimental and computational analysis revealed the stereospecificity of the isomerization reaction and quantified the bond-weakening effect through transition state analysis.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Physical
Philip R. D. Murray, Isabelle Nathalie-Marie Leibler, Sandrine M. Hell, Eris Villalona, Abigail G. Doyle, Robert R. Knowles
Summary: We introduce a two-component annulation strategy that involves the combination of aryl alkenes and redox-active radical precursors bearing tethered nucleophiles, enabling the synthesis of a diverse collection of five- and six-membered saturated heterocycles. This strategy employs an Ir(III) photocatalyst and a Bronsted acid under visible-light irradiation. The synthesis involves reductive proton-coupled electron transfer, radical addition to alkene, oxidative radical-polar crossover, and cyclization of the tethered nucleophile. This approach allows the easy access to a wide range of heterocycles, including pyrrolidines, piperidines, tetrahydrofurans, morpholines, delta-valerolactones, and dioxanones. It is amenable to gram-scale preparation and complex fragment coupling.
Editorial Material
Chemistry, Multidisciplinary
Alexandra D. Easley, Alison Mangano, Brett P. Fors
Summary: Polyurethanes (PUs) are synthesized materials commonly made from isocyanates, diols, and water. Water plays a crucial role in the production of carbon dioxide (CO2) used for self-blowing of the foams. To address safety concerns, researchers have explored alternative chemistries, and cyclic carbonate systems have shown great promise. In a recent study, Bourguignon, Grignard, and Detrembleur demonstrated that a cyclic carbonate and diamine system can generate CO2 for self-blowing through hydrolysis, allowing for a wide range of physical and thermo-mechanical properties. This work represents a significant advancement towards safer and more environmentally friendly PUs.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Yunjung Baek, Adam Reinhold, Lei Tian, Philip D. Jeffrey, Gregory D. Scholes, Robert R. Knowles
Summary: This study reports 11 isolable singly reduced iridium chromophores. Chemical reduction of a cyclometalated iridium complex with potassium graphite yields a 19-electron species. Structural and spectroscopic characterizations reveal a ligand-centered reduction product. The reduced chromophore exhibits wide light absorption and photoinduced bimolecular electron transfer reactivity.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Suong T. T. Nguyen, Lydia R. R. Fries, James H. H. Cox, Yuting Ma, Brett P. P. Fors, Robert R. R. Knowles
Summary: This research presents a catalytic, light-driven method for chemically recycling thiol epoxy thermosets to their original monomer at ambient temperature. The method involves the proton-coupled electron transfer (PCET) activation of hydroxy groups within the polymer network, generating alkoxy radicals that promote polymer fragmentation. The method efficiently depolymerizes insoluble thiol epoxy thermosets into small-molecule products that can be converted back to the original monomer. This research marks an important development in the recyclability of epoxy thermosets and demonstrates the potential of PCET for sustainable end-of-life management of commercial plastics.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Guanqi Qiu, Chi-Li Ni, Robert R. Knowles
Summary: We report a diagnostic framework for elucidating the mechanisms of photoredox-based hydrogen isotope exchange (HIE) reactions based on hydrogen/deuterium (H/D) fractionation. The traditional thermal HIE methods proceed by reversible bond cleavage and bond reformation steps, while light-driven HIE reactions can proceed via multiple, non-degenerate sets of elementary steps. The fractionation method presented here extracts information regarding the nature of the key bond-forming and bond-breaking steps.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Eric P. Geunes, Jonathan M. Meinhardt, Emily J. Wu, Robert R. Knowles
Summary: We report a light-driven method for the intermolecular anti-Markovnikov hydroamination of alkenes with primary heteroaryl amines. This method exhibits broad functional group tolerance and good reactivity. The reported method has important application value for pharmaceutically relevant heteroaryl amines.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Benjamin G. Hejna, Jacob M. Ganley, Huiling Shao, Haowen Tian, Jonathan D. Ellefsen, Nicholas J. Fastuca, Kendall N. Houk, Scott J. Miller, Robert R. Knowles
Summary: We present a highly enantioselective radical-based hydroamination of enol esters with sulfonamides using an Ir photocatalyst, Bronsted base, and tetrapeptide thiol. The reaction produces 23 protected β-amino-alcohol products with selectivities up to 97:3 er. Experimental and computational studies reveal that hydrogen bonding, π-π stacking, and London dispersion interactions play important roles in substrate recognition and enantioinduction.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Polymer Science
Shelby L. Shankel, Tristan H. Lambert, Brett P. Fors
Summary: Cationic reversible addition-fragmentation chain transfer (RAFT) polymerizations can be conducted at room temperature and do not require rigorous conditions, producing high-quality polymers that can be easily modified.