Iodine(III)-based halogen bond donors for recognition and organocatalysis in solution

• Applicant: Professor Dr. Stefan Huber
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556199713

In the last decade, halogen bonding (XB) has found several applications in molecular recognition as well as in organocatalysis. Particularly the class of iodine(III)-based XB donors, typically cyclic diaryliodonium salts, has proven to be very promising in both fields due to its special properties: In organocatalysis, these donors showed very high activity compared to their iodine(I)-based congeners. In molecular recognition, the fact that such an XB donor feature two orthogonal binding sites was utilized for biaxial binding, i.e. the selective recognition of geometrically fitting substrates containing two Lewis basic functional groups. In this project, these applications will be further developed and will especially also be extended to asymmetric processes. In the first part of the project, biaxial recognition will be extended towards new binding partners: dicarbonyl-substituted allenes. These intrinsically chiral compounds are suitable for chiral recognition using new chiral monodentate iodine(III)-based XB donors. Furthermore, this topic will be combined with organocatalysis via the activation of the substrates for chemical transformations by the strong biaxial coordination. In suitable reactions, this catalysis will also be performed in asymmetric fashion. In the second part of the project, the synthesis and application of new chiral and bidentate iodine(III)-based XB donors will be explored. The chiral information in these catalysts will be conformationally fixed via annelated ring systems. Due to the challenging synthesis, the synthetic methods will be developed on test systems: achiral congeners of the planned dicationic and bidentate target structures will first be synthesized. In parallel, the methods for chiral derivatization of the backbone will be developed. Afterwards, the synthesis of the chiral catalysts will be performed, which will then be tested in known benchmark reactions of (asymmetric) XB catalysis. Based on the results, the structure of the catalysts will be further optimized so that in the long-term they can be applied in reactions which have not been activated via halogen bonding before. The rational exploitation of the special advantages of iodine(III)-based XB donors compared to the classical iodine(I) systems in asymmetric catalysis and chiral recognition will represent an important contribution to establish this non-covalent interaction much more broadly in these fields.

• DFG Programme: Research Grants