Iron-Catalysed Oxygenation with O2
Lead Research Organisation:
University of Liverpool
Department Name: Chemistry
Abstract
Being used in the catalytic production of more than half of all the commercial chemicals, oxidation is one of the most significant industrial reactions, second only to polymerisation. Not surprisingly, the U.S. Department of Energy identified selective oxidation of organic chemicals to be the most important research area to impact the future chemical industry. However, it remains "one of the reactions with the greatest potential for improvement", primarily because of the low selectivity encountered in the vast majority of oxidation reactions and the widespread use of stoichiometric, toxic and hazardous oxidants, such as CrO3, H2S2O8, PhIO, HNO3. Using catalysts and environmentally benign oxidants is undoubtedly the most realistic way to address these issues. In this regard, developing iron-catalysed aerobic oxidation is most appealing, due to the unrivalled advantage of abundance, low cost and benign nature of Fe and O2. However, although iron-containing metalloenzymes are capable of selectively oxidizing various substrates with O2 under mild conditions, few man-made iron catalysts are known that can catalyse efficient, selective aerobic oxidation.
We recently uncovered a novel class of well-defined iron complexes bearing pyridine bisimidazoline (PyBisulidine) ligands, which allow for highly chemoselective oxygenation of ethers and olefins. Building on this success, this project seeks to develop the next generation of more active iron catalysts for selective oxygenation of more challenging substrates. In particular, we will concentrate on two reactions, depolymerisation of lignin and cleavage of aliphatic C=C double bonds, under aerobic conditions. These reactions, which are vastly different in nature and can thus demonstrate the wide scope of the iron catalysts, are of both fundamental and commercial significance.
Lignin is the only natural polymers made of aromatic units and could be used to produce a wide range of platform aromatic compounds. However, this requires the depolymerisation of the lignin ether linkage in the first place. Considering the huge scale of any possible processes toward this end, the catalyst to be used should ideally be based on a cheap metal such as iron.
Oxidative cleavage of alkenes into carbonyls is a widely used transformation. However, ozone is most often used in industrial operations, and this comes with the well-known safety issues of explosivity, the cost of special equipment, and the large amount of waste generated. Thus, there has been a strong incentive to develop catalytic methods to replace ozone. Iron-based catalysts are particularly interesting, considering not only the environmental benefit of iron but also the ability of iron oxygenases to oxidize olefins to carbonyl compounds with exquisite selectivity.
For both of these reactions, few iron catalysts are known that can make use of O2 as oxidant. The Fe-PyBisulidine complexes are expected to bring about a step change in addressing these challenges.
The new catalysts will find applications in other reactions as well. The ether linkage is one of the most ubiquitous bonds found in nature and manmade chemicals, ranging from pharmaceuticals and agrochemicals through household products to lignin and coal. Thus, using the new catalysts and O2, compounds containing an ether bond may be transferred into highly value-added products, and polluting plastics, agrochemicals and detergents may be degraded in air. To further demonstrate the value of the iron catalyst, collaboration with a SME to produce, via acylation of arenes, compounds of direct business interest will be implemented.
We recently uncovered a novel class of well-defined iron complexes bearing pyridine bisimidazoline (PyBisulidine) ligands, which allow for highly chemoselective oxygenation of ethers and olefins. Building on this success, this project seeks to develop the next generation of more active iron catalysts for selective oxygenation of more challenging substrates. In particular, we will concentrate on two reactions, depolymerisation of lignin and cleavage of aliphatic C=C double bonds, under aerobic conditions. These reactions, which are vastly different in nature and can thus demonstrate the wide scope of the iron catalysts, are of both fundamental and commercial significance.
Lignin is the only natural polymers made of aromatic units and could be used to produce a wide range of platform aromatic compounds. However, this requires the depolymerisation of the lignin ether linkage in the first place. Considering the huge scale of any possible processes toward this end, the catalyst to be used should ideally be based on a cheap metal such as iron.
Oxidative cleavage of alkenes into carbonyls is a widely used transformation. However, ozone is most often used in industrial operations, and this comes with the well-known safety issues of explosivity, the cost of special equipment, and the large amount of waste generated. Thus, there has been a strong incentive to develop catalytic methods to replace ozone. Iron-based catalysts are particularly interesting, considering not only the environmental benefit of iron but also the ability of iron oxygenases to oxidize olefins to carbonyl compounds with exquisite selectivity.
For both of these reactions, few iron catalysts are known that can make use of O2 as oxidant. The Fe-PyBisulidine complexes are expected to bring about a step change in addressing these challenges.
The new catalysts will find applications in other reactions as well. The ether linkage is one of the most ubiquitous bonds found in nature and manmade chemicals, ranging from pharmaceuticals and agrochemicals through household products to lignin and coal. Thus, using the new catalysts and O2, compounds containing an ether bond may be transferred into highly value-added products, and polluting plastics, agrochemicals and detergents may be degraded in air. To further demonstrate the value of the iron catalyst, collaboration with a SME to produce, via acylation of arenes, compounds of direct business interest will be implemented.
Planned Impact
Oxidation is one of the most significant industrial chemical reactions, second only to polymerisation. Not surprisingly, the U.S. Department of Energy identified selective oxidation of organic chemicals to be the most important research area to impact the future chemical industry. However, it is still "one of the reactions with the greatest potential for improvement", primarily because of the low selectivity encountered in the vast majority of oxidation reactions and the widespread use of stoichiometric hazardous oxidants. Indeed, "The economic potential for improvements in this area is enormous - for example, modest improvement in selectivity could lead to annual savings of several billions of dollars in the industry". Using able iron catalyst and O2 as oxidant is the most appealing option to realise clean, economic oxidation, because of their unrivalled abundance, low cost and benign nature.
Economic
1. The availability of the new iron catalysts could lead to the development of innovative, clean, and more economic iron-based catalytic oxidation processes for advanced pharmaceutical, agrochemical and chemical manufacturing, e.g. in the production of building blocks and APIs for drug discovery and manufacturing and for platform chemicals from renewable biomass, benefiting the wider chemical industry.
2. SMEs such as Liverpool ChiroChem can benefit from the new catalytic technology that delivers the products both economically- and environmentally-consciously and thus more competitively.
3. The outcome of the project may also benefit environmental protection by providing cheap less toxic catalysts that could be used to catalyse the aerobic degradation of polluting plastics, agrochemicals and detergents and/or provide a new direction for finding more viable catalysts.
4. The wider chemical producing and using industries will also benefit from the outcome, either through using the catalysts or lowered cost in chemicals.
5. The catalysts and the reactions enabled will also provide licensing opportunities for fine chemical and catalyst manufacturers for large scale production and spinout opportunities.
Societal
1. The new iron chemistry will lead to more efficient production of e.g. consumer goods, pharmaceuticals and agrochemicals.
2. The chemistry will benefit the environmental through the use of clean oxidant, and reduction in waste, by-products and energy usage.
3. The protocol developed may be taken directly or further developed for degrading environmentally polluting substances such as polyethers, contributing to environmental remediation.
4. Highly skilled personnel adept in catalyst science will be trained, who are essential to maintain the vibrant, inventive research community that is essential to a knowledge-based society/economy.
4. The knowledge gained will be disseminated, providing a new strategy to do clean oxidation reactions and to enable other researchers to develop viable base metal catalysts for many other oxidation reactions.
5. Research collaborations with academic groups and companies will be strengthened to allow for continued search for more economic catalysts and study of more challenging reactions.
Economic
1. The availability of the new iron catalysts could lead to the development of innovative, clean, and more economic iron-based catalytic oxidation processes for advanced pharmaceutical, agrochemical and chemical manufacturing, e.g. in the production of building blocks and APIs for drug discovery and manufacturing and for platform chemicals from renewable biomass, benefiting the wider chemical industry.
2. SMEs such as Liverpool ChiroChem can benefit from the new catalytic technology that delivers the products both economically- and environmentally-consciously and thus more competitively.
3. The outcome of the project may also benefit environmental protection by providing cheap less toxic catalysts that could be used to catalyse the aerobic degradation of polluting plastics, agrochemicals and detergents and/or provide a new direction for finding more viable catalysts.
4. The wider chemical producing and using industries will also benefit from the outcome, either through using the catalysts or lowered cost in chemicals.
5. The catalysts and the reactions enabled will also provide licensing opportunities for fine chemical and catalyst manufacturers for large scale production and spinout opportunities.
Societal
1. The new iron chemistry will lead to more efficient production of e.g. consumer goods, pharmaceuticals and agrochemicals.
2. The chemistry will benefit the environmental through the use of clean oxidant, and reduction in waste, by-products and energy usage.
3. The protocol developed may be taken directly or further developed for degrading environmentally polluting substances such as polyethers, contributing to environmental remediation.
4. Highly skilled personnel adept in catalyst science will be trained, who are essential to maintain the vibrant, inventive research community that is essential to a knowledge-based society/economy.
4. The knowledge gained will be disseminated, providing a new strategy to do clean oxidation reactions and to enable other researchers to develop viable base metal catalysts for many other oxidation reactions.
5. Research collaborations with academic groups and companies will be strengthened to allow for continued search for more economic catalysts and study of more challenging reactions.
Publications
Guan R
(2023)
Chemoselective Decarboxylative Oxygenation of Carboxylic Acids To Access Ketones, Aldehydes, and Peroxides.
in Organic letters
Guan R
(2022)
Decarboxylative oxygenation of carboxylic acids with O 2 via a non-heme manganese catalyst
in Green Chemistry
Huang Z
(2022)
Non-heme manganese( ii ) complex-catalysed oxidative cleavage of 1,2-diols via alcohol-assisted O 2 activation
in Green Chemistry
Huang Z
(2022)
Chemical Recycling of Polystyrene to Valuable Chemicals via Selective Acid-Catalyzed Aerobic Oxidation under Visible Light.
in Journal of the American Chemical Society
Huang Z
(2021)
Oxidative Cleavage of Alkenes by O2 with a Non-Heme Manganese Catalyst.
in Journal of the American Chemical Society
Zhou J
(2022)
Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst
in Angewandte Chemie
Zhou J
(2022)
Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst.
in Angewandte Chemie (International ed. in English)
Description | Being used in the catalytic production of more than half of all the commercial chemicals, oxidation is one of the most significant industrial reactions, second only to polymerisation. However, "oxidations still remain poorly understood chemical transformations" and it is still "one of the reactions with the greatest potential for improvement", primarily because of the low selectivity encountered in the vast majority of oxidation reactions and the widespread use of stoichiometric, hazardous oxidants. In research supported by this award, we have discovered molecular catalysts based on cheap, benign manganese that catalyse selective oxidation of olefins, alcohols and carboxylic acids with molecular oxygen, the most easily available and benign oxidant. In addition, we discovered a simple acid catalytic system that enables upcycling of waste polystyrene to pure, high-value chemicals. The major achievements are: 1) discovery of a catalytic system for oxidative cleavage of various olefin C=C double bonds, 2) discovery of a catalytic system for oxidative cleavage of diols, 3) extension of the catalysis to oxidative decarboxylation of carboxylic acids, 4) discovery of a simple photocatalytic method that uses a cheap Bronsted acid as catalyst for upcycling of waste polystyrene to pure benzoic acid, and 5) preliminary discovery of a catalytic system for oxidative cleavage of rubber polymers. The results arising from 1-4 have been published. The discoveries in 4 and 5 prompted us to submit three grant applications in 2020-2022 (EPSRC and RSC), which were unfortunately not funded. The study on polystyrene upcycling was highlighted by multiple international media outlets, e.g. Chemical & Engineering News (the American Chemical Society), ChemistryViews, J. Am. Chem. Soc (JACS). Spotlights, X-Mol, Nature Synthesis, Synfacts, and as one of the most viewed JACS articles. |
Exploitation Route | The discovery of oxidative cleavage of olefins and diols is expected to be of use to pharmaceutical and fine chemical synthesis. Our discovery of rubber cleavage may interest those dealing with waste plastics, and our discovery of hydrocarbon oxidation may interest those involved in commodity chemicals manufacturing. Our further study has led to a new, simple method for upcycling waste polystyrene, which has attracted a great deal of academic attention and should inspire the development of new strategies to address the issues of waste plastics. |
Sectors | Chemicals Creative Economy Education Environment Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology |
URL | https://cen.acs.org/environment/recycling/Cheap-catalysts-recycle-polystyrene-valuable/100/web/2022/04 |
Description | Synthetic plastics have been widely used to improve the quality of people's lives. A big challenge is that most of them are not recycled and do not degrade, causing severe environmental issues, such as soil and water contamination and air pollution. An example is polystyrene (PS), which has been widely used in our daily life from building materials, electronics, protective packaging, to food containers. Millions of tonnes of PS are produced annually, but most are not recycled. Since all atoms of PS are connected by strong C-C and C-H bonds, PS is remarkably inert and difficult to degrade. This award enabled a novel chemical recycling method to be developed by the group of Xiao and collaborators. Driven by light, a simple Bronsted acid is found to catalyse the oxidative cleavage of various waste PS to valuable chemicals, such as benzoic acid and formic acid, under 1 bar of O2. Requiring no photosensitizers and only mild reaction conditions, the protocol is operationally simple, and has also been demonstrated in a flow system. EPR and DFT investigations indicate that singlet oxygen, produced probably by an acid-PS adduct acting as a photosensitizer, is the reactive oxygen species, which abstracts a hydrogen atom from a tertiary C-H bond in PS, leading to hydroperoxidation and subsequent C-C bond cracking events. "The novel approach and mechanistic understanding offered in this work could be pivotal in upcycling polystyrene materials on an industrial scale, incentivizing better recovery and management of the millions of tons of annual polystyrene waste", as commented in J. Am. Chem. Soc. (JACS) Spotlights. The work has been published in JACS (2022, 144, 6532-6542) and featured in C&EN, ChemistryViews, JACS Spotlights, X-Mol, Nature Synthesis and Synfacts etc, and is one of the most viewed/cited JACS papers. |
First Year Of Impact | 2022 |
Sector | Chemicals,Education |
Impact Types | Societal |
Description | Highlights of the study by multiple international media outlets |
Geographic Reach | Multiple continents/international |
Policy Influence Type | Citation in systematic reviews |
URL | https://cen.acs.org/environment/recycling/Cheap-catalysts-recycle-polystyrene-valuable/100/web/2022/... |
Description | EPSRC IAA |
Amount | £15,000 (GBP) |
Funding ID | EP/R511729/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 09/2021 |
End | 06/2022 |
Description | KNOWLEDGE TRANSFER PARTNERSHIP between The University of Liverpool and Liverpool ChiroChem Limited |
Amount | £192,866 (GBP) |
Funding ID | KTP11214 |
Organisation | Innovate UK |
Sector | Public |
Country | United Kingdom |
Start | 01/2019 |
End | 01/2022 |
Description | Single-Coordination-Site Catalysts for Asymmetric Reduction |
Amount | £29,400 (GBP) |
Organisation | AstraZeneca |
Sector | Private |
Country | United Kingdom |
Start | 09/2019 |
End | 09/2023 |
Title | CCDC 1997610: Experimental Crystal Structure Determination |
Description | Related Article: Zhiliang Huang, Craig M. Robertson and Jianliang Xiao|2020|CSD Communication||| |
Type Of Material | Database/Collection of data |
Year Produced | 2020 |
Provided To Others? | Yes |
URL | http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc251p1z&sid=DataCite |
Title | CCDC 2046040: Experimental Crystal Structure Determination |
Description | Related Article: Jimei Zhou, Minxian Jia, Menghui Song, Zhiliang Huang, Alexander Steiner, Qidong An, Jianwei Ma, Zhiyin Guo, Qianqian Zhang, Huaming Sun, Craig Robertson, John Bacsa, Jianliang Xiao, Chaoqun Li|2022|Angew.Chem.,Int.Ed.|61|e202205983|doi:10.1002/anie.202205983 |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc26p299&sid=DataCite |
Title | CCDC 2046041: Experimental Crystal Structure Determination |
Description | Related Article: Jimei Zhou, Minxian Jia, Menghui Song, Zhiliang Huang, Alexander Steiner, Qidong An, Jianwei Ma, Zhiyin Guo, Qianqian Zhang, Huaming Sun, Craig Robertson, John Bacsa, Jianliang Xiao, Chaoqun Li|2022|Angew.Chem.,Int.Ed.|61|e202205983|doi:10.1002/anie.202205983 |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc26p2bb&sid=DataCite |
Title | CCDC 2046042: Experimental Crystal Structure Determination |
Description | Related Article: Jimei Zhou, Minxian Jia, Menghui Song, Zhiliang Huang, Alexander Steiner, Qidong An, Jianwei Ma, Zhiyin Guo, Qianqian Zhang, Huaming Sun, Craig Robertson, John Bacsa, Jianliang Xiao, Chaoqun Li|2022|Angew.Chem.,Int.Ed.|61|e202205983|doi:10.1002/anie.202205983 |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc26p2cc&sid=DataCite |
Title | CCDC 2050295: Experimental Crystal Structure Determination |
Description | Related Article: Zhiliang Huang, Renpeng Guan, Muralidharan Shanmugam, Elliot Leon Bennett, Craig M. Robertson, Adam Brookfield, Eric J.L. McInnes, Jianliang Xiao|2021|CSD Communication||| |
Type Of Material | Database/Collection of data |
Year Produced | 2021 |
Provided To Others? | Yes |
URL | http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc26thk3&sid=DataCite |
Description | Single-Site Catalysts for Asymmetric Reduction |
Organisation | AstraZeneca |
Country | United Kingdom |
Sector | Private |
PI Contribution | Our work in asymmetric catalysis including asymmetric hydrogenation with chiral iron catalysis contributed to the continuous collaboration with AstraZeneca and this funding. |
Collaborator Contribution | AstraZeneca supported the collaboration by providing advice on the project and financial assistance for a PhD student and experiments, and by co-supervising the student and offering placement to the student. |
Impact | None yet. |
Start Year | 2019 |
Description | Invited talk |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | The PI gave an invited talk on "Activation of O2 and H2 for catalysis - examples from our research" at the International Conference on Frontier Materials 2022 (online). |
Year(s) Of Engagement Activity | 2022 |
URL | http://www.icfm.org.cn/ |
Description | Plenary Lecture |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Plenary Lecture at the 13th International Symposium on Activation of Dioxygen and Homogeneous Oxidation Catalysis, China, which was attended by a few hundreds of people internationally. |
Year(s) Of Engagement Activity | 2018 |
Description | Talk at Beijing University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Postgraduate students |
Results and Impact | An invited talk on dioxygen activation was given at the College of Chemistry and Molecular Engineering, Beijing University, 2019. |
Year(s) Of Engagement Activity | 2019 |