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Selective Decarboxylative Fluorination of β-Keto Acids in Aqueous Media: 19F-NMR-Assisted Batch Optimization and Transfer to Continuous Flow

E. Cermjani,* C. Deckers, M. Maskos, T. H. Rehm*: Selective decarboxylative fluorination of β-keto acids in aqueous media: 19F-NMR-assisted batch optimization and transfer to continuous flow. Chem. Eur. J. 2025, 31, e202404435, DOI: 10.1002/chem.202404435

© Fraunhofer IMM

The synthesis of API relevant α-fluoro ketone phenacyl fluoride is finally described as a catalyst-free continuous flow process. This selective decarboxylative monofluorination is optimized in batch mode for aqueous and biocompatible conditions varying temperature, additives, and pH. Furthermore, benchtop NMR PAT was used for fundamental studies to a better understanding of the mechanism of the decarboxylative fluorination as well as the reaction pathways to α-difluorinated ketone derivatives.

Publication

Hydrogen Peroxide Producing Titania-Silica Supraparticles as Tailorable Photocatalysts for Flow Chemistry Reactions in Microfluidic Reactors

B. Herbig,* E. Cermjani, D. Hanselmann, A. Schmitt, C. Deckers, T. H. Rehm, K. Mandel, S. Wintzheimer: Hydrogen peroxide producing titania-silica supraparticles as tailored photocatalysts for flow chemistry reactions in microfluidic reactors. Chem. Bio. Eng. 2025, 2, 199-209, DOI: 10.1021/cbe.4c00154

© Susanne Wintzheimer, Fraunhofer ISC

The development of hybrid catalysts for cascade reactions that demonstrate high efficiency and longevity strongly relies on the precise arrangement of the individual components within such a material. This guarantees both their proximity for enhanced interaction and, at the same time, sufficient separation avoiding mutual harm. Before the acutal design of a usually very complex hybrid catalyst, it is essential to study and understand the impact of structural characteristics on catalytic activities of each catalytically active constituent separately. This study thus focuses on a comprehensive structure–activity analysis of the component within a highly customizable TiO2-SiO2 material, which produces H2O2 photocatalytically. The tailorable design of the hybrid material is achieved through the utilization of the spray-drying process. The H2O2 productivity of the obtained so-called TiO2-SiO2 supraparticles is demonstrated in both a batch and a flow reactor, marking a crucial step toward their future application as hybrid catalysts in photoassisted cascade reactions

Publication

Diazonium Salts in Visible Light Photocatalysis – a Focused Overview of their Application in Continuous Flow Synthesis

C. Deckers, T. H. Rehm*: Diazonium salts in visible light photocatalysis - A focused overview on their application in continuous flow synthesis. ChemPhotoChem 2025, asap, DOI: 10.1002/cptc.202400405

© TOC graphic designed by Lisa Pokropp (Fraunhofer IMM)

The combination of continuous flow technology and visible light photocatalysis has been used to improve the safety and productivity of reactions with diazonium salts as reactive intermediates. This approach has proven to be a reliable method for various organic synthesis routes with diazonium salts under mild and well-defined conditions. 

Publication

Light- and Plasma-Induced Catalysis Made in Germany Promises Great Opportunities for the Chemical Industry: Sustainability, Economic Viability, and Competitiveness

Position paper by the Fraunhofer Groups “Light & Surfaces,” “Materials,” and “Resource Technology and Bioeconomy,” 2025

© Fraunhofer IGB

Germany is facing a historic opportunity: breakthroughs in catalysis can modernize our production chains and promote prosperity, sustainability, and security. With our solid foundational knowledge and excellence in engineering, manufacturing, and technology, we are well-positioned to utilize renewable energies as new fuels. Innovative concepts that employ light and plasma enable chemical processes at lower temperatures and pressures, leading to significant energy savings.

The societal benefits are enormous: residual-free recycling, clean air and water, and highly efficient medicines are just a few of the possibilities of a sustainable industry "Made in Germany." Initial successes, such as hydrogen production from sunlight and the use of microorganisms for sustainable raw materials, demonstrate the immense potential of these developments.

To initiate this revolution, we need a strategic funding policy that supports interdisciplinary networks and innovative pilot projects. Let us work together to shape the change and establish Germany as a leader in catalysis!

Position paper (in german)

Are you looking for solutions for complex chemical processes?

© Fraunhofer IME

Advancing Catalysis and Continuous Process Design
This concise summary offers insights into our latest developments in catalyst synthesis, reactor design, and the implementation of continuous cascade processes – key technologies for efficient and scalable chemical production.

Drawing on our multidisciplinary expertise, we support partners from concept to pilot scale with customized solutions tailored to their specific process requirements.


Download the full PDF to learn more – and contact us directly to explore how we can help bring your process ideas to life.

Cascade reactions for the continuous flow synthesis of fine chemicals

Cascade reactions in flow

© Fraunhofer IMM

In recent years, cascade reactions have become a highly interesting topic of academic research. Such multi-step chemical transformations have the potential of high synergy by combining different catalysis methods within one reaction sequence. A particular interesting synergy results from the combination of photocatalysis and biocatalysis as both methods perform under mild process conditions and can provide reactive intermediates via photocatalysis with subsequent usage in the enzymatic step. In the ILLUMINATE project, a consortium of four Fraunhofer institutes investigate the transfer of photo- and biocatalyzed cascade reactions from batch to flow by developing novel multi-step catalyst materials and continuous flow reactors.

Spray Drying Symposium 4/24 Poster

Cascade reactions for the continuous flow of fine chemicals

The catalysts required for synthesis are immobilized on transparent films
© Fraunhofer IGB
The catalysts required for synthesis are immobilized on transparent films

ILLUMINATE: Innovative cascade reactions for sustainable chemical production The ILLUMINATE project, an interdisciplinary research project involving four Fraunhofer Institutes, is investigating the combination of photocatalysis and biocatalysis in multi-stage cascade reactions. Through the synergy of these two gentle catalyst techniques, chemical transformations can be carried out under mild conditions, improving both the efficiency and sustainability of the processes.

The project focuses on the transfer of these reactions from batch processes to continuous flow processes. To this end, hybrid catalysts are being developed that combine the advantages of both catalytic methods, and work is being done on optimizing flow reactors that enable scalable, efficient and resource-saving production. Of particular importance is the immobilization of enzymes on carrier particles to make the catalysts more stable and reusable.

The project has the potential to revolutionize the production of fine chemicals and active pharmaceutical ingredients (APIs) by developing new, more environmentally friendly production methods for the chemical industry. An important goal is to transfer these technologies from research to industrial practice and thus make a sustainable contribution to the chemical production of the future.

ILLUMINATE - Cascade reactions in flow: a novel process window in fine chemicals synthesis (poster)

Polymeric foils as key element of the falling film microreactor: A concept study for enabling scalable heterogeneous catalysis in flow

© Fraunhofer IMM

Cascade reactions are revolutionizing the way fine chemicals are synthesized. In the ILLUMINATE project, four Fraunhofer institutes join forces to explore a powerful synergy: combining photocatalysis and biocatalysis in continuous flow. This downloadable PDF offers deep insights into the development of novel catalyst materials, a new generation of falling film microreactors, and the implementation of transparent, structured polymer foils for flexible, scalable catalysis.

Learn how advanced materials, modular reactor concepts and precise light control pave the way for efficient, multi-step reaction processes under mild conditions – ideal for pharmaceuticals and beyond.

Download the full PDF to explore the technological vision, experimental design, and next steps for innovative flow chemistry solutions.

Milestones for hybfrid - catalysis in Cascade (poster)

In situ Diazonium Salt Formation and Photochemical Aryl-Aryl Coupling in Continuous Flow Monitored by Inline NMR Spectroscopy

C. Deckers,* T. H. Rehm*: In situ Diazonium Salt Formation and Photochemical Aryl-Aryl Coupling in Continuous Flow Monitored by Inline NMR Spectroscopy. Chem. Eur. J. 2024, 30, e202303692, DOI: 10.1002/chem.202303692 Front cover web link: https://doi.org/10.1002/chem.202401747

© Fraunhofer IMM

Diazonium trifluoroacetates for biphenyls are an underrated aryl radical source for the photochemical aryl-aryl coupling. This concept does not require any additional catalysts to perform an efficient and selective reaction. The photoarylation is supported by the application of Flow Chemistry using microreactors and modern LED technology. An integrated benchtop NMR spectrometer enables real-time analysis of the substituted products.

Publication

Polymeric foils as key element of the falling film microreactor: A concept study for enabling scalable heterogeneous catalysis in flow

© Fraunhofer IMM

Introduction Fluorination, involved in the synthesis of fine chemicals like active pharmaceutical ingredients (APIs), represents a useful tool for improving both pharmacodynamics and pharmacokinetics. Fluorine as the most electronegative atom enables precise alteration of nearby functional groups, which can affect the bioavailability of pharmaceutical agents. Their interaction with the active site of their appropriate target protein can be enhanced by fluorine insertion, which alter conformational preferences, thus potentially improving drug efficiency. [1] Several fluorination methods show drawbacks regarding atom economy and efficiency, so there is still a need to develop an efficient and selective synthesis for fluorinated compounds.

Polymeric foils as key element of the falling film microreactor: A concept study for enabling scalableheterogeneous catalysis in flow (Poster)

Selective Decarboxylative Mono- and Difluorination of ß-Ketoacids in Continuous Flow Mode

© Fraunhofer IGB

The reliable production of fine chemicals is a key component of the pharmaceutical industry – especially to ensure the continuous and safe supply of vital medicines to the population. At the same time, the chemical industry faces fundamental challenges in the face of rising energy prices and the necessary transition to more sustainable production processes.

A promising approach to meeting these complex requirements lies in the combination of continuous flow synthesis with microreaction technology. These technologies enable more precise, safer, and more resource-efficient synthesis of fine chemicals.

Microstructured reactor systems create a clearly defined process environment in which gaseous, liquid, and solid reactants – such as catalysts – interact under precisely controlled conditions. Compared to traditional batch processes, flow chemistry offers several key advantages:

Selective Decarboxylative Mono- and Difluorination of b-Ketoacids in Continuous Flow Mode (Poster)

Flow chemistry opens up new avenues

Sichtbares Licht als Energiequelle für die photokatalysierte Umsetzung von CO2 an Diamantoberflächen.
© Fraunhofer IGB

The safe production of fine chemicals is a top priority for the pharmaceutical industry in order to ensure a reliable supply of medicines for the population. In addition, the chemical industry is facing new challenges with the energy crisis and the transition to sustainable production. Flow synthesis in combination with microreaction technology can contribute to solving this complex situation, as these methods enable the safe and more sustainable synthesis of fine chemicals.

German article:

Durchflusschemie eröffnet neue Wege • CHEManager 05/2023

Reactor Technology Concepts for Flow Photochemistry

T. H. Rehm*: Reactor Technology Concepts for Flow Photochemistry. ChemPhotoChem 2020, 4, 235-254, DOI: 10.1002/cptc.201900247

© Fraunhofer IMM

Photon2Flow: In the last decade, photochemistry has experienced a renaissance which has had fundamental impact on academic research. In conjunction, the growing acceptance and application of continuous flow technology in the chemical community has resulted in a most fruitful alliance to date and has revolutionized “thinking and doing chemistry” with light as a delicate energy source.

Publication

Flow Photochemistry as a Tool in Organic Synthesis

T. H. Rehm*: Flow Photochemistry as a Tool in Organic Synthesis. Chem. Eur. J. 2020, 26, 16952-16974, DOI: 10.1002/chem.202000381

© Fraunhofer IMM

Photon4FlowSynthesis: Continuous-flow technology and photochemistry have joined forces recently to overcome physical restrictions in the synthesis of complex organic molecules. As result of this fruitful combination, flow photochemistry has become a reliable methodology in the portfolio of modern organic synthesis under mild and defined conditions.

Publication