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TAN, Choon Hong

Professor
Chair, School of Physical and Mathematical Sciences

Education: B.Sc. (Hons), First Class, National University of Singapore , PhD, University of Cambridge

Research Area: Synthetic Organic Chemistry, Green Chemistry

Phone: 6316 8761

E-mail:choonhong@ntu.edu.sg

Webpage:http://www.ntu.edu.sg/home/choonhong



Research Interest

Practical Asymmetric Synthesis: Chiral Brønsted Base Catalyst and Chiral Phase Transfer Catalyst

Practical asymmetric catalysis is of growing importance to our modern society. Enantiomers can have very different biological activity. In the 1960s, the tragic administration of a racemic mixture of thalidomide to pregnant women, a drug prescribed to reduce the symptoms of morning sickness, results in severe birth defects. One form of the drug is the sedative but the wrong enantiomer is strongly tetragenic. In 1992, US Food and Drug Administration, USA issued a guideline to encourage the use of single enantiomer drugs. In 2000, the worldwide sales of single enantiomer compounds/drugs reached US$123 billion. The reason why not all drugs are prepared in the enantiomerically pure form is that the technology required for cheap, simple and effective chemical synthesis of the chiral form of drugs is still not fully established. The development of enantiomerically pure compounds not only impact medicines but is of growing importance to other important segments of our modern society including the healthcare of animals, crop protection, food and beverage industries, materials and fragrance industries.
In recent years, we are interested to develop general and practical Chiral Brønsted Base Catalyst and Chiral Phase Transfer Catalyst illustrated below.

 

Green and Environmentally Friendly Chemistry

Green chemistry is defined as the design of chemical processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture and use. Combining technological progress with the safeguard of the environment is one of the challenges of the new millennium. It is recognized that the science of chemistry is fundamental to addressing the problems facing the environment and attainment of sustainable development. Green chemistry technologies provide a number of benefits, including reduced waste hence eliminating costly end-of-the-pipe treatments, safer products and reduced use of energy and resources. The success of environmentally friendly reactions, products, and processes will improve the competitiveness within the chemical industry, as well as meet the needs of the environment and the people.
In recent years, we are interested to develop Organic Dye-Photocatalyzed Reactions as illustrated below:




Selected Representative Publications

  1. J. Shen, T. T. Nguyen, Y.-P. Goh, W. Ye, X. Fu, J. Xu and C.-H. Tan, Chiral Bicyclic Guanidine Catalyzed Enantioselective Reactions of Anthrones. Journal of the American Chemical Society, 2006, 128, 13692–13693.

  2. D. Leow, S. Lin, S. K. Chittimalla, X. Fu and C.-H. Tan, Enantioselective Protonations Catalyzed by Chiral Bicyclic Guanidine, Angewandte Chemie International Edition English, 2008, 47, 5641–5645.

  3. H. Liu, D. Leow, C.-H. Tan, Enantioselective Synthesis of Chiral Allenes by Guanidine-Catalyzed Isomerization of Alkynes, Journal of the American Chemical Society, 2009, 131, 7212–7213. (Highlighted by Synfacts 2009, 7, 0794-0794; contributors: Benjamin List, Steffen Müller)

  4. Z. Jiang, Y. Pan, Y. Zhao, T. Ma, R. Lee, Y. Yang, K.-W. Huang, M. W. Wong and C.-H. Tan, Synthesis of Chiral Quaternary C-F Bond through Highly Enantioselective and Diastereoselective Guanidine-Catalyzed Addition of Fluorocarbon Nucleophiles, Angewandte Chemie International Edition, 2009, 48, 3627–3631. (Designated by Editors as Hot paper)

  5. T. Ma, X. Fu, C. W. Kee, L. Zong, Y. Pan, K.-W. Huang, C.-H. Tan, Pentanidium Catalyzed Enantioselective Phase Transfer Conjugate Addition Reactions, Journal of the American Chemical Society, 2011, 133, 2828–2831. (Highlighted by Synfacts 2011, 5, 0556-0556; contributors: Benjamin List, Saihu Liao)

  6. J. Wang, J. Chen, C. W. Kee, C.-H. Tan, Bicyclic Guanidine-Catalyzed Enantiodivergent γ-Selective Asymmetric Allylic Amination, Angewandte Chemie International Edition, 2012, 51, 2382 –2386.