From Molecular Iodine to Chiral Catalysts - Systematic Applications of Halogen-Bonding in Organocatalysis

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The research will advance the field of halogen bonding and its systematic application in organic synthesis. Specifically, we will focus on the development of stereoselective halogen-bond-catalyzed reactions and the design of the required chiral catalysts. So far, halogen bonding has successfully been employed in different field of chemistry including organic catalysis, but stereoselective transformations caused by halogen bonds are scarce. To close this gap, we combine classical physical-organic and spectroscopic techniques and computational investigations with synthetic experiments. We will identify chiral additives that are capable of complexing molecular iodine, one of the simplest halogen-bond donors, to create a chiral environment that results in enantioselective transformations. Furthermore, we will construct a Lewis-acidity scale for different halogen-bond motifs that allows us to identify promising candidates for catalysis. Those catalysts will complement the currently employed proline- or prolinol-derived structures. We demonstrate the activity of these newly identified catalysts in important organocatalytic transformations.Therefore, our investigations offer on the one hand a new perspective on the field of organocatalysis by the introduction of new motifs. On the other hand, the physical-organic analysis will provide deep insights into crucial aspects of this unexplored noncovalent interaction.