Chemical manufacturing is vital to the global economy, but current production methods rely on precious materials and lengthy synthetic sequences that generate excessive waste and carbon dioxide (CO2) emissions. To lower the environmental impact of chemical production, sustainable chemical transformations are required.
Dedicated to revolutionising chemical manufacturing is Associate Professor Koh Ming Joo from NUS Chemistry. He has, for example, designed iron catalysts for alkene dialkylation, the process of converting alkenes into alkanes. The use of iron as a catalyst in this reaction is appealing not only because iron is abundant and inexpensive, but it is also environmentally friendly compared to other metals like palladium or platinum. However, its ability to adopt multiple oxidation and spin states makes it difficult to facilitate chemical bond formation between iron and other atoms.
Assoc Prof Koh has however made iron-catalysed alkene dialkylation possible using a mechanism whereby iron mediates the addition of alkyl groups through a process that leverages radicals, which are reactive species containing unpaired electrons. This approach enables high regioselectivity (control over where the groups are added) and the formation of previously hard-to-access molecular structures, which in turn allows for the construction of complex hydrocarbon frameworks. These are highly valuable in pharmaceutical and agrochemical applications.
Assoc Prof Koh’s group is also involved in developing sustainable, photochemistry-based methods to produce biorelevant carbohydrates and glycoconjugates. For example, they introduced a biomimetic strategy that simplifies the synthesis of glycosyl compounds (carbohydrates) by directly transforming native sugars without the need for multiple steps and harsh reagents or conditions. This innovation, which harnesses mild visible light irradiation conditions, not only reduces waste but also has potential applications in drug discovery and protein glycosylation.
A testament to his significant contributions to chemistry, Assoc Prof Koh became the first Singaporean scientist to receive the Novartis Early Career Award in Chemistry in 2023. This accolade highlights the global impact of his research and underscores Singapore’s growing influence in the scientific community.
Ultimately, he hopes to develop transformative and sustainable chemical reactions that can modify functional molecules to provide access to new chemical structures that will bring enormous benefits to industries such as pharmaceuticals and agrochemicals.
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Jiang, Y., Wei, Y., Zhou, Q.-Y., Sun, G.-Q., Fu, X.-P., Levin, N., Zhang, Y., Liu, W.-Q., Song, X., Mohammed, S., Davis, B. G. & Koh, M. J. (2024). Direct radical functionalization of native sugars. Nature, 631, 319-327.
Tan, T.-D., Serviano, J. M. I., Luo, X., Qian, P.-C., Holland, P. L., Zhang, X. & Koh, M. J. Congested C(sp3)-rich architectures enabled by iron-catalysed conjunctive alkylation. (2024) Nat. Catal. 7, 321-329.
Liu, C.-F.; Wang, Z.-C.; Luo, X.; Lu, J.; Ko, C. H. M.; Shi, S.-L. & Koh, M. J. (2022). Synthesis of tri- and tetrasubstituted stereocentres by nickel-catalysed enantioselective olefin cross-couplings. Nat. Catal. 5, 934-942.
Wang, H., Liu, C.-F., Martin, R. T., Gutierrez, O. & Koh, M. J. (2022). Directing group-free catalytic dicarbofunctionalization of unactivated alkenes. Nat. Chem. 14, 188-195.
Yu, X., Zhao, H., Xi, S., Chen, Z., Wang, X., Wang, L., Lin, L. Q. H., Loh, K. P. & Koh, M. J. (2020) Site-selective alkene borylation enabled by synergistic hydrometallation and borometallation. Nat. Catal. 3, 585-592.
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