Project Area B
Lewis/Brønsted acid-base interactions, ionic interactions and hydrogen bonds
The projects in this section are thematically connected by a defined, weak interaction within an assembly, like the interaction of Lewis acids and Brønsted acids, ionic interaction and hydrogen bonds.
Chemistry I/TUM
B01: Chromophore Activation by Lewis Acid Coordination
The aim of the project is to comprehensibly explore how Lewis acids modulate the photophysical properties of a given chromophore in an assembly and how this modulation can be exploited for unprecedented selective photochemical reactions. There are three work packages (WPs): The first WP revolves around the photochemical activation of bonds within assemblies of boron-based Lewis acids and Lewis-basic nitrogen compounds, most notably pyridine. The second WP addresses enantioselective photochemical reactions catalyzed by chiral oxazaborolidine Lewis acids. The final WP aims at a dearomatization of benzene derivatives by photocycloaddition at the arene core.
Organic Chemistry, Synthesis
Publications
Key Publications:
Grünwald, Dominik; Mohan Jayakumari, Chithra; Jeremias, Noah; Zuber, Julian; Stein, Christopher J.; Bach, Thorsten: Catalytic Enantioselective [6π] Photocyclization Reactions by Chromophore Activation with a Chiral Lewis Acid. J. Am. Chem. Soc. 147 (50), 2025, 46525-46534
Yan, Peng; Stegbauer, Simone; Wu, Qinqin; Kolodzeiski, Elena; Stein, Christopher; Lu, Ping; Bach, Thorsten: Enantioselective Intramolecular ortho Photocycloaddition Reactions of 2‐Acetonaphthones. Angew. Chem. Int. Ed. 63, 2024, e202318126
Schwinger, Daniel P.; Peschel, Martin T.; Rigotti, Thomas; Kabaciński, Piotr; Knoll, Thomas; Thyrhaug, Erling; Cerullo, Giulio; Hauer, Jürgen; de Vivie-Riedle, Regina; Bach, Thorsten: Photoinduced B–Cl Bond Fission in Aldehyde-BCl3 Complexes as a Mechanistic Scenario for C–H Bond Activation. J. Am. Chem. Soc. 144, 2022, 18927-18937
B02: Hydrogen Bonds and Ion Pairs in Enantioselective Photochemistry
Hydrogen bonds serve as non-covalent interactions to temporarily recruit substrates in an assembly with a photocatalyst. The project revolves around two catalyst classes displaying directed bonding motifs and providing a chiral cavity in which enantioselective photochemical reactions can occur. In work package 1, a lactam/amide binding motif will be employed for substrate coordination, and the catalysts display an azabicyclo[3.3.1]nonan-2-one backbone connected to a single chromophore. In work package 2, chiral phosphoric acids will be used, with the option to install one or two photocatalytic entities at the backbone rendering the catalysts either C1or C2 symmetric.
Organic Chemistry, Synthesis
Publications
Key Publications:
Pflaum, Niklas; Pauls, Mike; Kumar, Ajeet; Kutta, Roger Jan; Nuernberger, Patrick; Hauer, Jürgen; Bannwarth, Christoph; Bach, Thorsten: Oxetane Cleavage Pathways in the Excited State: Photochemical Kinetic Resolution as an Approach to Enantiopure Oxetanes. J. Am. Chem. Soc. 147, 2025, 13893-13904
Stierle, Max; Jaschke, Constantin; Grenda, Daniel; Peschel, Martin; Pickl, Thomas; Gessner, Niklas; Nuernberger, Patrick; Fingerhut, Benjamin; Ochsenfeld, Christian; de Vivie-Riedle, Regina; Bach, Thorsten: Enantioselective Photochemical Generation of a Short‐Lived, Twisted Cycloheptenone Isomer: Catalytic Formation, Detection, and Consecutive Chemistry. Angew. Chem. Int. Ed. 64, 2025, e202501433
Kutta, Roger Jan; Großkopf, Johannes; van Staalduinen, Nils; Seitz, Antonia; Pracht, Philipp; Breitenlechner, Stefan; Bannwarth, Christoph; Nuernberger, Patrick; Bach, Thorsten: Multifaceted View on the Mechanism of a Photochemical Deracemization Reaction. J. Am. Chem. Soc. 145, 2023, 2354-2363
B04: Selenium Photo-π-Acid Catalysis
The proposed research aims to harness the unique chemical behavior of selenium-centered, spin-correlated radical pair assemblies to generate potent photo-π-acid catalysts for the chemoselective redox functionalization of apolar alkenes. The fundamental mechanistic principle, around which the proposed work revolves, is the formation of catalytically active ion pairs from geminal radical pairs through a thermophotonically or photothermally stimulated doublet-doublet electron transfer (i.e., tp-or pt-SDET). The SDET occurs on a picosecond timescale, rendering the subsequent chemistry of the incipient photo-π-acid catalysts insensitive to undesired, diffusion-controlled side reactions.
Organic Chemistry, Synthesis
Publications
Key Publications:
Frank, Eduard; Flügel, Jana L.; d’Heureuse, Ludwig; Woick, Sophie; Breder, Alexander: Enantioconvergent Synthesis of Diarylmethane Drugs via Privileged Benzhydrol Intermediates, J. Org. Chem. 91, 2026, 793-797.
B06: Selective Bond Activation by Modulation of Proton-Coupled Electron Transfer (PCET) and Hydrogen Atom Transfer (HAT)
B07: Radical Generation with Semiquinoid Flavin Catalysts and their Ring-Contracted Analogues
B08: Proving Pre-Association by Transient Spectroscopy on Multiple Timescales
Pre-association between photocatalyst and substrate is a crucial advantage for a photocatalytic reaction, as the potential losses associated with diffusion-limited steps are avoided. Proving such pre-association under synthetically relevant conditions can be difficult. We will implement and apply novel spectroscopic tools to prove and improve pre-association in photocatalytic reactions in collaboration with partners from theory and synthesis. The methods of choice are multiscale transient absorption – from femtoseconds to microseconds – and transient absorption anisotropy.
Physical Chemistry, Spectroscopy
Prof. Dr. Jürgen Hauer
Publications
Current Publications:
Bahukhandi, Srishti B.; Klein, Andreas S.; Mustafa, Ghulam; Weyh, Maria; Walter, Alexandra; Thyrhaug, Erling; Hauer, Jürgen; Storch, Golo; Zeymer, Cathleen: The Natural Redox Cofactor Pyrroloquinoline Quinone (PQQ) Enables Photocatalytic Radical Cyclizations. Angew. Chem. Int. Ed. 2025, 64, e202505431, doi.org/10.1002/anie.202505431
Key Publications:
Schwinger, Daniel P.; Peschel, Martin T.; Rigotti, Thomas; Kabaciński, Piotr; Knoll, Thomas; Thyrhaug, Erling; Cerullo, Giulio; Hauer, Jürgen; de Vivie-Riedle, Regina; Bach,Thorsten: Photoinduced B–Cl Bond Fission in Aldehyde-BCl3 Complexes as a Mechanistic Scenario for C–H Bond Activation. Journal of the American Chemical Society 2022, 144, 18927-18937, doi.org/10.1021/jacs.2c06683.
Keil, Erika; Malevich, Pavel; Hauer, Jürgen: Achromatic frequency doubling of supercontinuum pulses for transient absorption spectroscopy. Opt. Express 2021, 29, 39042-39054, doi.rog/10.1364/OE.442400.
Kumar, Ajeet; Malevich, Pavel; Mewes, Lars; Wu, Shangze; Barham, Josua P.; Hauer, Jürgen: Transient absorption spectroscopy based on uncompressed hollow core fiber white light proves pre-association between a radical ion photocatalyst and substrate. The Journal of Chemical Physics 2023, 158, 144201, doi/org/10.1063/5.0142225.
