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NUS Graduate School for Integrative Sciences and Engineering Research Project Write-up Title of Project : Practical, Asymmetric Redox-Neutral Chemical Synthesis via Borrowing Hydrogen Name of Supervisor : ZHAO Yu Contact Details: Email: [email protected] Telephone: 65-65167964 Short Description Synthetic chemistry is considered to be the “central science” as it provides the toolbox for various applied areas such as pharmaceuticals, chemical biology and material science. Due to resource constraints, the current trend in synthetic chemistry is not simply about preparing molecules of specific interest, but rather on how to prepare them in a highly efficient and economical manner. The concept of “redox economy” which focuses on minimizing synthetic steps that only adjust the oxidation state of the intermediates without generating structural complexity is an important consideration at the strategic level for chemical synthesis, and redox-neutral transformations that circumvent such redundant oxidation/reduction steps are highly sought after as environmentally benign and sustainable processes. Scheme a illustrates the process for the production of amines, which are ubiquitous functionality in pharmaceuticals and agrochemicals. Traditionally, amines can be produced from the more readily available alcohols through a multi-step process involving oxidation of alcohol to ketone, condensation with amine to imine followed by reduction. As both the oxidation and reduction steps in this process utilize stoichiometric reagents, much waste is generated. The concept of “borrowing hydrogen” has thus proven to be much more efficient: the alcohol starting material can be directly converted to the amine product in one step without the need for any external reagent! Recent research efforts in our group have led to the realization of the first enantioselective variant of this reaction to convert readily available alcohols to chiral amines that are highly valuable in drug development. Scheme b showcases one impressive example that the mixture of four isomers in the alcohol starting material was converted to essentially one pure isomer of the chiral amine product! Two catalysts utilized in this process include a chiral iridium complex and achiral phosphoric acid. The focus of the future studies is to develop truly simple and efficient catalytic systems to realize such transformations as well as more important ones. For example, the conversion of 1,2-diols (again as a mixture of isomers) to diastereo- and enantiopure 1,2-diamines will be the holy grail of this area of research. The realization of such processes will have a profound impact in academic research as well as chemical industry.