Periodic Reporting for period 5 - FRICatANIONS (Frontiers in Catalytic Anion-Binding Chemistry)
Berichtszeitraum: 2022-06-01 bis 2023-05-31
There is a continuous demand of new, more general and efficient methodologies to overcome unsolved synthetic challenges towards a sustainable society, in which catalysis represents a key and central approach. In this context, anion-binding has very recently emerged as a new type of activation, opening new frontiers and enabling the discovery of unprecedented reactivities. Although the effects of anions in catalytic processes are still largely unknown, this mode of chemical activation might be the key for the future design of more efficient synthetic transformations. Thus, both a better understanding and the design of innovative synthetic technologies embracing the anion-binding concept will be essential for the advance of this field and the development of highly efficient and sustainable synthesis.
The ultimate objective of the FRICatANIONS project is the innovation, development and establishment of anion-binding processes as a universal tool in catalysis and synthesis. To achieve that, the design of novel catalyst structures and diverse aspects in modern catalytic synthetic chemistry, including organo-, metal-, and photocatalysis, will be addressed in order to enhance the efficiency and understanding of reactions involving anions.
The ultimate objective of the FRICatANIONS project is the innovation, development and establishment of anion-binding processes as a universal tool in catalysis and synthesis. To achieve that, the design of novel catalyst structures and diverse aspects in modern catalytic synthetic chemistry, including organo-, metal-, and photocatalysis, will be addressed in order to enhance the efficiency and understanding of reactions involving anions.
In this project, binding and mechanistic studies on the family of helical chiral tetrakistriazole H-donor catalysts have been performed, which have led to key information and a better understanding of their unique performance. This has led to the design of a second generation of catalysts presenting tunable side-chains that can further interact with the reactants by additional hydrogen-bonding or pi-interactions. Furthermore, a new class of non-covalent anion-binding catalysts based on the more directional and potent halogen bonding interactions has been also developed. With all these innovative catalytic structures, new methodologies in the field of anion-binding asymmetric organocatalysis towards valuable fine chemicals could be developed, for which other known NH-based hydrogen-bond donor or halogen-bond donor catalysts were unsuccessful to date. For example, the scope on heterocyclic substrates could be broaden to challenging derivatives, while remote activation and modulation of highly promiscuous nucleophiles could be achieved by exploiting the multidentate nature of our catalytic systems. Moreover, the first highly enantioselective halogen-bonding catalysis was developed by a careful design of catalyst-substrate interactions. Finally, preliminary proof-of-concept studies on the application of anion-binding processes in other type of catalyses such as metal- and photocatalysis have led to the discovery of novel reactivities and applications in non-covalent catalysis, which should further pursue towards enantioselective processes. The results of this project have been actively disseminated in conferences and lectures, as well as in workshops, by all members of the team and associated members supporting the research activities of the program. Moreover, this project served as an internationally esteemed platform that have led to a high recognition of the importance of the field of anion-binding, now been considered and included as an important type of activation mode in catalysis. This was reflected by the Wiley-VCH book “Anion-binding Catalysis” edited by the PI of this ERC-project, as well as the invitation to include a chapter on the topic in the classic book “Asymmetric Organocatalysis” (Wiley-VCH, Ed. Dalko), a reference for scientist working in catalysis.
We could show that there is a need of structural novel anion-binding catalyst in order to achieve and discover unprecedent reactivities and selectivities. Although it was possible to demonstrate new applications of anion-binding organocatalysis beyond the state of the art, anion-binding offers enormous, unexploited possibilities for the activation of organic and metallic molecules. Thus, the extension of anion-binding activation approaches to other types of important catalyses involving dual or cooperative catalysis is expected. In particular, a proof of concept for metal- and for photo-cocatalysis with anion-binding has been achieved and these results will be published in due course. Moreover, the development of novel chiral halogen-bonding catalysts based on our design within the tetrakistroazole backbone has led for the first time to high, synthetically valuable enantioselectivities with this type of non-covalent activation mode, opening new venues in asymmetric sigma-hole catalysis. We believe that all these findings will provide beyond the end of the project important new catalytic approaches and tools for more efficient synthesis and allow the design of unconventional synthetic routes.