AtropFluoPhoto · Stereoselective Synthesis of Atropisomeric Fluorophores for Asymmetric Photocatalysis

Stereoselective Synthesis of Atropisomeric Fluorophores for Asymmetric Photocatalysis

Manufacturing has regained its strategic significance as a key component of modern economy in recent years worldwide. In Europe, the pharmaceutical and chemical industries make up a substantial share of the gross domestic product (GDP).(1) For a sustainable production, a new generation of chemical synthetic technologies must be developed for the advanced manufacturing of pharmaceuticals and other high value chemicals. In this context, one of the current challenges is to develop green and innovative catalysis approaches to selectively access optically enriched functional molecules. The proposed research hence aims to explore asymmetric catalysis that will allow for novel and cost-effective protocols for the rapid construction of chiral heterocyclic fluorophores. In view of these, with the generous support of MSCA-IF (Project ID: 840456) from European Commission, Dr. Xingxing Wu has conducted two-year postdoctoral research under the supervision of Prof. Christof Sparr in Department of Chemistry, University of Basel, attempting to challenge the above issue by developing stereoselective control strategy for atropisomeric acridinium fluorophore synthesis. The acridiniums are particularly useful scaffolds in numerous fields, such as probes, bioimaging, and design of dynamic supramolecular systems.(2) Recently, the 9-arylated acridinium fluorophores, have been demonstrated by Fukuzumi and Nicewicz to be very powerful visible light photocatalysts due to their remarkable redox properties.(3,4) The general acridiniums, as well as other xanthene dyes, are typically symmetric and do not allow stereoinduction. Given the fact that axially chiral (hetero)aryl-(hetero)aryl compounds are broadly applicable in stereoselective catalysis serving either as catalysts or ligands,(5) in this contribution, we develop a stereoselective method to prepare atropoisomeric acridinium fluorophores with a stereogenic axis for the first time. This study would lead to the significant understanding on the axially chiral fluorophore system which has rarely been explored before. 1 CIA World Factbook. last updated on January 20, 2018. 2 Y.-C. Lin, C.-T. Chen, Org. Lett. 2009, 11, 4858. 3 N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116, 10075. 4 A. Tlili, S. Lakhdar, Angew. Chem. Int. Ed. 2021, doi: 10.1002/anie.202102262. 5 J. Clayden, W. J. Moran, P. J. Edwards, S. R. LaPlante, Angew. Chem. Int. Ed. 2009, 48, 6398.

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