Research in the Xiao group is mainly concerned with homogeneous catalysis for sustainable chemical synthesis. The focal point of our research is on discovering and developing innovative catalytic methods, aiming at:
1. Faster, more productive and greener organic synthesis.
2. Building molecular complexity from simple, renewable molecules.
3. Gaining molecular-level understanding of the catalytic machinery.
We devise molecular metal catalysts and engineer the catalytic systems for target reactions, and we do this by a cross-disciplinary approach, harnessing chemistry from organometallics through synthetic organic chemistry to physical chemistry, and by close collaboration with academic colleagues and industrialists.
We are currently working on:
1. Selective oxidation with molecular oxygen, focusing on developing able biomimetic metal catalysts to activate dioxygen and making use of the catalysts for potential fine/commodity chemical manufacturing.
2. Reduction via hydrogen transfer, focusing on using renewable, easy-to-handle molecules as hydrogen/electron as well as carbon source for hydrogenation reactions and beyond.
3. Biomass for value-added chemicals, focusing on converting biomass into fine/commodity chemicals via molecular catalysis.
The examples below are illustrative of our research in the recent past:
Aerobic oxidation with bio-relevant metal catalysts. Molecular Fe and Cu and more recently Mn catalysts have been developed, which allows for the selective oxygenation of a range of organic compounds under 1 bar of O2.
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References:
1) A. Gonzalez-de-Castro, et al, J. Am. Chem. Soc. 2014, 136, 8350−8360.
2) A. Gonzalez-de-Castro, et al, J. Am. Chem. Soc. 2015, 137, 8206−8217.
3) Y. Liu, et al, Chem. Eur. J. 2017, 23, 3051-3061.
4) Y. Liu, et al, Chem. Eur. J. 2017, 23, 3062-3066.
New catalysts for hydrogenation and dehydrogenation. Cyclometalated Cp*Ir(III) and Cp*Rh(III) complexes have been found to be excellent catalysts for selective hydrogenation and dehydrogenation of a wide range of compounds. The iridacycles are commercially available at Apexmolecular.
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References
1) J. Wu, et al, Angew. Chem. Int. Ed. 2013, 52, 6983-6986.
2) D. Talwar, et al, Angew. Chem. Int. Ed. 2015, 54, 5223-5227.
3) C. Wang, et al, Angew. Chem. Int. Ed. 2010, 49, 7948-7552.
3) For a review, see C. Wang, et al, Chem. Commun. 2017, 53, 3399-3411.
Mechanistic understanding of molecular catalysis. In studying the Heck reaction, we discovered that oxidative addition, one of the most fundamental reactions in organometallic chemistry and catalysis, can be accelerated by hydrogen bonding, and the regioselectivity of the reaction, with origin from another fundamental organometallic transformation, i.e. insertion, can be controlled by hydrogen bonding via simple hydrogen bond-donating media.
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In our study of transfer hydrogenation, earlier we discovered that water accelerates asymmetric transfer hydrogenation (ATH), and the ATH rate and selectivity are a function of solution pH and hence controllable. Continued study led to the finding of counteranion-controlled enantioselective hydrogenation of imino bonds and reductive amination, and to the elucidation of the hydrogenation mechanism, particularly the anion-participated transition state that determines the enantioselectivity.
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References
1) J. Ruan, et al, J. Am. Chem. Soc. 2010, 132, 16689-16699.
2) For a review, see J. Ruan, et al, Acc. Chem. Res., 2011, 44, 614-626.
3) C. Li, et al, J. Am. Chem. Soc. 2009,131,6967-6969.
4) W. Tang, et al, Angew. Chem. Int. Ed. 2013, 52, 1668-1672.
Profs. Chao Wang, Dong Xue, Chaoqun Li and Weijun Tang, Shaanxi Normal University.
Dr. Jon Iggo, University of Liverpool.
Profs. Tao Zhang and Zhangzhi Li, Dalian Institute of Chemical Physics.
Prof. Lijin Xu, Renmin University.
Prof. Yong Yang, Qingdao Institute of Bioenergy and Bioprocess Technology.
Prof. Ming Lei, Beijing University of Chemical Technology.
Prof. Eric Mcinnes, University of Manchester.
Prof Samuel De Visser, University of Manchester
Dr. Jingya Yang, Northwest Normal University
XJTU-Liverpool Joint Laboratory of Chemistry and Chemical Engineering, Xi’an Jiaotong University.
LCC
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