Towards Absolute Asymmetric Synthesis

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With this award, the Chemical Synthesis Program of the NSF Division of Chemistry is supporting research by Professor Tehshik Yoon of the University of Wisconsin–Madison’s Chemistry Department. Professor Yoon is interested in controlling the shape of molecules. Many important organic molecules, including drug molecules and elementary biomolecules such as amino acids and sugars can exist in either left- or right-handed forms. These two mirror-image forms interact with biological systems in very different ways, so it is critically important to control the handedness in the synthesis of organic molecules. Professor Yoon leads a team of undergraduate and graduate students to investigate if light can be used to control the handedness of organic molecules. To do so, they have created a family of catalysts that absorb light and then induce molecular transformations with excellent control over the shape of the resulting products. This work takes an interdisciplinary approach combining multiple areas of the chemical sciences. In addition, students in the Yoon laboratory working on this project are helping to disseminate scientific research to novice science students by producing a new podcast. The first season of this podcast has been downloaded over 2500 times through a variety of free podcasting platforms.The chiral photocatalysts in this project are octahedral iridium complexes whose ligands are arranged about the metal with well-defined helical chirality. This class of compounds constitutes an attractive starting point for these studies: they possess a robust and well-studied photochemistry; they are quite effective photosensitizers for a range of organic transformations; and they can easily be synthesized in stereochemically pure form. The newly designed chiral photosensitizers resulting from these studies are remarkably efficient asymmetric catalysts, and a multidisciplinary approach to studying their reactions reveals a rich variety of mechanisms. These studies offer a training opportunity for a diverse group of undergraduate and graduate students in scientific fields of significant contemporary interest to the chemical industries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.