Bach Lab | TUM

Dearomatization of Aromatic Carbonyl Compounds by Photocycloaddition Reactions to 1,1-Dimethylallene The photocycloaddition of 1,1-dimethylallene to various aromatic carbonyl compounds was found to occur exclusively at the benzene core. While the reaction with methyl 2-methoxybenzoate resulted in a mixture of products resulting from ortho, meta, and para photocycloaddition, acetophenone and its 4-substituted derivatives delivered the respective para photocycloaddition products in 50–58% yields. For 2-methoxyacetophenone, an ortho photocycloaddition initiated a reaction cascade, which led to bicyclic products by the incorporation of a nucleophile in 29–74% yields.

Our new paper on the dearomatization of aromatic carbonyl compounds by photocycloaddition is out now in Organic Letters @pubs.acs.org Congratulations, Luis, for your excellent work 💡🙌💫 #photochemistry pubs.acs.org/doi/10.1021/...

Photochemical Cyclization of Tertiary Buta‐2,3‐dienamides to β‐Lactams Upon Triplet Energy Transfer Energy transfer is the key to the successful photocyclization of the title compounds to 3,4-disubstituted 2-azetidinones. If the substituent at the nitrogen atom is primary (R2 = H), trans products a...

We're very proud to announce our newest publications on the photochemical cyclization of tertiary buta-2,3-dienamides to β-lactams! A big thanks to the collaborators from the Kerzig Group (@ckerzig.bsky.social) @angewandtechemie.bsky.social #photochemistry 💡🙌🧑‍🔬
onlinelibrary.wiley.com/doi/10.1002/...

We're very happy to welcome our new Postdoc Dr. Rachel Cantrell! We wish you best of luck for your research 🌟💡👩‍🔬 #photochemistry #WomeninSTEM

Photochemical Deracemization of Chromanes and its Application to the Synthesis of Enantiopure Bioactive Compounds Various substituted chromane-2-carboxamides were successfully deracemized by employing a chiral benzophenone (BP, 10 mol%) as photocatalyst and an achiral thiol as additive (20 mol%). The method was ...

Check out our newest publication on the photochemical deracemization of chromanes! Amazing work @bikig6.bsky.social Out now in @angewandtechemie.bsky.social 💡🌟 #photochemistry #deracemization
doi.org/10.1002/anie...

Enantioselective Intramolecular C–H Alkylation Catalyzed by a Nonsymmetric Chiral Cobalt Porphyrin Upon catalysis (1 mol %) by a chiral cobalt porphyrin, quinazolinones with a tethered diazo alkane precursor underwent an enantioselective C–H alkylation at carbon atom C4. Formation of five-, six-, a...

Congratulations to the Bach group (@bach-lab.bsky.social) for this very nice Co-catalyzed asymmetric C-H alkylation, to which we contributed a few DFT calculations: pubs.acs.org/doi/10.1021/...

Enantioselective Intramolecular C–H Alkylation Catalyzed by a Nonsymmetric Chiral Cobalt Porphyrin Upon catalysis (1 mol %) by a chiral cobalt porphyrin, quinazolinones with a tethered diazo alkane precursor underwent an enantioselective C–H alkylation at carbon atom C4. Formation of five-, six-, a...

We're very excited to announce our new publication on enantioselective intramolecular C-H Alkylation with Nonsymmetric Chiral Cobalt Porphyrin! Out now in @jacs.acspublications.org 💡🧪https://pubs.acs.org/doi/10.1021/jacs.5c19047

We kicked off the season with an early Christmas party this year and truly enjoyed the evening together with some of our alumni 🌟 Wishing everyone a smooth December and cozy winter days ahead 🎁🎄 #chemistry #alumni #holidays

Congratulations to our newly minted PhD Dr. Max Stierle! We are very proud of you and we will miss you! 🧪💡🎓 #phd #graduation #photochemistry

We're very excited to welcome our new Postdoc Rahul, our PhD student Ji Won, and our newest Master's student Luis to our group. Best of luck for your research!💡🧑‍🔬🥽 #PhDLife #Research #Teamwork

We were very happy to have Todd Hyster from Princeton University as a speaker for the CRC325 lecture series yesterday. Thank you for your inspiring talk about photoenzymatic catalysis! 💡🧪 #crc_325 #enzyme #princeton

Photochemical deracemization of 2,3-allenoic acids mediated by a sensitizing chiral phosphoric acid catalyst Photochemistry opens the possibility to convert a racemic mixture of a chiral compound into a distinct enantiomer in a single operation. Seven chiral phosphoric acids with a pendant thioxanthone chrom...

Another contribution to photochemical deracemization! Check out Max' outstanding work on chiral phosphoric acids, out now in @chemicalscience.rsc.org! 💡🧑‍🔬🧪
#photochemistry #CPA #deracemization
doi.org/10.1039/D5SC...

Photocatalytic reductive incorporation of carbon dioxide into double bonds Carbon dioxide (CO2) is a challenging molecule to incorporate into olefins due to its inherent inert properties. Silanes have now been shown to rapidly react selectively with CO2, catalysed by the…

Another recent most read article, from @bach-lab.bsky.social

'Photocatalytic reductive incorporation of carbon dioxide into double bonds' 🔓

Congratulations to our amazing soccer team for winning the championship of the @tum.de NAT tournament! Despite heavy rain in the end, you kept fighting and brought the trophy back home. 🏆🥇⚽ #Soccer #TUM #winner

Kinetic Resolution of Heterocyclic Lactams by a Photocatalytic Cobalt-Catalyzed Dehydrogenation Chiral heterocyclic lactams have been kinetically resolved in a photochemical process that involves selective hydrogen abstraction by a chiral benzophenone catalyst. Recognition of one enantiomer is ...

Great news! Check out our latest paper on the co-catalytic photochemical kinetic resolution by dehydrogenation. Amazing work, Chao! 💡🙌🧪 #photochemistry #dehydrogenation #kineticresolution

doi.org/10.1021/jacs.5c07524

What an amazing day at the Campus Run 2025! 🏃‍♀️🏃‍♂️
So proud of everyone who took part! Huge participation and great energy all around.
Special shoutout to Simone for finishing 3rd fastest woman over 11 km! 🔥
Big thanks to our awesome cheer squad 🫶 You really made a difference! 💙💪
#CampusRun #Race #TUM

Efficient and selective energy transfer photoenzymes powered by visible light - Nature Chemistry Recent studies have shown that energy transfer photoenzymes can be engineered to promote stereocontrolled [2 + 2] cycloadditions; however, existing systems rely on ultraviolet light and display limite...

Amazing work, Johannes! Check out his contribution to the work of the Green Group from @uommib.bsky.social on ennatioselective photoenzymatic C-H insertion of quinolones, out now in @natchem.nature.com! #photochemistry #photoenzyme #enantioselective💡🧬🥳

www.nature.com/articles/s41...

First defense of the year: Congratulations to freshly minted Dr. Niklas Pflaum! Excited to have you for a few more months with us #PhD #graduation 🎓👏💡

Oxetane Cleavage Pathways in the Excited State: Photochemical Kinetic Resolution as an Approach to Enantiopure Oxetanes Chiral spirocyclic oxetanes [2-oxo-spiro(3H-indole-3,2′-oxetanes)] were subjected to irradiation in the presence of a chiral thioxanthone catalyst (5 mol %) at λ = 398 nm. An efficient kinetic resolut...

Excited to share the news: Niklas' paper on enantiopure oxetanes is out now in @jacs.acspublications.org. Great work by all and big thanks to all collaboration partners! 💡👏 #photochemistry #enantioselectivity

doi.org/10.1021/jacs...

Happy 60th birthday, Thorsten! 🎂🍾🎈 Thank you for being an amazing PI, for all your support and motivation. We hope there will be many more happy occasions to celebrate with you in the future. We wish you all the best for your next 60 years 😇😁 #birthday #celebration #60years

Photocatalytic Reductive Incorporation of Carbon Dioxide into Double Bonds Carbon dioxide (CO2) is a challenging molecule to incorporate into olefins due to its inherent inert properties. Silanes have now been shown to rapidly react selectively with CO2, catalysed by the presence of a caesium base, to form formate salts which can undergo a hydrogen atom transfer (HAT) to give the d

Interested in photochemical activation of carbon dioxide? Check out Mark's work by using sequential silylation/HAT of CO2! Out now in Chem. Commun. by @rsc.org. #photochemistry #carbondioxide 💡🫧

pubs.rsc.org/en/content/a...

Enantioselective Photochemical Generation of a Short‐Lived, Twisted Cycloheptenone Isomer: Catalytic Formation, Detection, and Consecutive Chemistry Cyclohept-2-enone-3-carboxylic acid undergoes a photochemical isomerization from its cis- to its trans-form either upon direct irradiation (λ = 366 nm) or in the presence of a triplet sensitizer (λ =...

New paper out now in @angewandtechemie.bsky.social! Congratulations Max on your successful project on photochemically induced Diels-Alder reactions of twisted cycloheptenones. Big thanks also to all collaboration partners! #photochemistry #enantioselective 💡👏

onlinelibrary.wiley.com/doi/10.1002/...

Welcome Veronika to our group! 🙌 Good luck for your Master's thesis on borylations. 👩‍🔬💫 #WomeninSTEM #catalysis

Intramolecular ortho Photocycloaddition of 4-Substituted 7-(4′-Alkenyloxy)-1-indanones and Ensuing Reaction Cascades 4-Substituted 7-(4′-alkenyloxy)-1-indanones were prepared from the respective substituted aryl propanoic acids and subjected to UV-A irradiation (λ = 350 or 366 nm). While the 4-chloro compound was directly converted at λ = 366 nm into a pentacyclic product (47% yield) by a three-photon cascade process, the oxygenated substrates reacted in trifluoroethanol at λ = 350 nm by a two-photon cascade, involving an ortho photocycloaddition, a thermal disrotatory ring opening, and a [4π] photocyclization (six examples, 67–82% yield). An ensuing photochemical di-π-methane rearrangement of the latter products was achieved by irradiation at λ = 350 nm in toluene (five examples, 36–70% yield). The diastereoselectivity of the reaction was probed employing a chiral 1-indanone with a stereogenic center at carbon atom C3. 1-Indanones with a 4-hexenyloxy side chain [(E)- or (Z)-configured] at carbon atom C7 served to interrogate the stereospecifity of the reaction.

Check out Audrey's work on ortho photocycloaddition reaction cascades published in JOC! #Photochemistry #WomeninSTEM 💡👩‍🔬
pubs.acs.org/doi/full/10....

We're very excited to have Dr. Charlotte Teschers as a Postdoc with a return grant in our lab. 🌟 We hope you enjoy your time with us and good luck for your future career as an independent researcher! 👩‍🔬🙌 #WomeninSTEM #chemistry

Another new member to the group: Welcome Nina! We wish you all the best for your PhD. #womeninstem👩🎓‍🔬

A big welcome to Florian who joined us for his PhD in February. Good luck for your project on photochemistry! 🧑‍🔬🎓

Stereochemical Editing at sp3-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer ConspectusMillions of chiral compounds contain a stereogenic sp3-hybridized carbon center with a hydrogen atom as one of the four different substituents. The stereogenic center can be edited in an increasing number of cases by selective hydrogen atom transfer (HAT) to and from a photocatalyst. This Account describes the development of photochemical deracemization reactions using chiral oxazole-annulated benzophenones with a bonding motif that allows them to recognize chiral lactam substrates by two-point hydrogen bonding. The backbone of the catalysts consists of a chiral azabicyclo[3.3.1]nonan-2-one with a U-shaped geometry, which enables substrate recognition to occur parallel to the benzoxazole part of the aromatic ketones. The photocatalysts facilitate a catalytic photochemical deracemization of several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, and 4,7-diaza-1-isoindolinones. In addition, if more than one stereogenic center is present, the editing delivers a distinct diastereoisomer upon the appropriate selection of the respective photocatalyst enantiomer. The chiral photocatalysts operate via the benzophenone triplet that selectively abstracts a properly positioned hydrogen atom in exclusively one of the two substrate enantiomers. The photochemical step creates a planar carbon-centered radical and erases the absolute configuration at this position. While returning HAT to the same position would likely recreate the stereogenic center with the same absolute configuration, spectroscopic and quantum chemical studies suggest that the hydrogen atom is delivered from the photocatalyst to a heteroatom that is in conjugation to the radical center. Two scenarios can be distinguished for the hydrogen atom shuttling process. For hydantoins, N-carboxyanhydrides, and 4,7-diaza-1-isoindolinones, the back HAT occurs to a carbonyl oxygen atom or an imine-type nitrogen atom which is not involved in binding to the catalyst. For oxindoles and 2,5-diketopiperazines, a single lactam carbonyl group in the substrate is available to accept the hydrogen atom. It is currently assumed that back HAT occurs to this group, although the carbonyl oxygen atom is involved in hydrogen bonding to the catalyst. In comparison to the former reaction pathway, the latter process appears to be less efficient and more prone to side reactions. For both cases, an achiral enol or enamine is formed, which delivers upon dissociation from the catalyst statistically either one of the two stereoisomers of the substrate. Since only one substrate enantiomer (or diastereoisomer) is processed, a high enantioselectivity (or diastereoselectivity) results. Even though the editing is a contra-thermodynamic process, the described decoupling of a photochemical and a thermal step allows the usage of a single catalyst in loadings that vary between 2.5 and 10 mol % depending on the specific mode of action.

Interested in stereochemical editing by photochemically triggered hydrogen atom transfer? Check out our latest review by Maxi 💡🧪
pubs.acs.org/doi/10.1021/...

Photochemical Deracemization of 4,7-Diaza-1-isoindolinones by Unidirectional Hydrogen Atom Shuttling By coupling a photochemical and a thermal step, a single chiral catalyst can establish a photostationary state in which the enantiopure form of a chiral compound is favored over its racemate. Followin...

Let's start our year with a new publication in #JACS: Check out Philip's work on photochemical deracemization of 4,7-diaza-1-isoindolinones. #Photochemistry #Deracemization💡
pubs.acs.org/doi/10.1021/jacs.4c16053

AK Bach goes Bluesky! We are excited to share our journey on photochemistry here. Follow us to stay updated!💡🥼 #Photochemistry #Organicchemistry #Science #Chemsky
ch.nat.tum.de/oc1