ITEM OF INTEREST  -  New dicationic organic photoredox catalyst for decarboxylation

19th October 2020

Ohkubo, Tobisu et al. developed a novel organic photocatalyst based on a phenylene-bridged bis(benzimidazolium) structure. The chromophore has broad absorption range with a maximum at approx. 290 nm tailing out to 500 nm. The novel photocatalyst can be used for the decarboxylative hydroxylation and dimersation of various carboxylic acids. This paper can be found in Chem. Sci., DOI: 10.1039/d0sc03958f.


ITEM OF INTEREST  -  Tandem photoisomerization-cyclization process for quinoline synthesis

1st October 2020

Baumann et al. apply LED technology for the UV light-induced E→Z isomerization of double bonds in 4-(2-aminophenyl)but-3-en-2-one derivatives with subsequent condensation to the corresponding quinoline in ethanol as green solvent. Beside substrate screening and scale up of precursor and quinoline systems, Baumann et al. also used flow technology for the selective hydrogenation of quinolines into tetrahydroquinolines. This paper can be found in Eur. J. Org. Chem., DOI: 10.1002/ejoc.202000957.


ITEM OF INTEREST  -  Photo-induced decarboxylation and denitrogenation in flow

30th September 2020

Adiyala, Kim et al. recently developed a continuous flow method for the annulation of L-prolin with α-azidochalcones. The authors apply as key steps the photo-induced decarboxylation and denitrogenation for the formation of α-amino radicals and 2H-azirine, which convert to the desired fused imidazole derivatives. The continuous flow mode outperformed the batch reaction both in process time and yield for all 20 examples tested. This paper can be found in Green Chem., DOI: 10.1039/C9GC03496J.


ITEM OF INTEREST  -  Cyclopentadien photo-oxidation with in situ-formed singlet oxygen in flow

29th September 2020

Pouwer, Allais et al. developed a scalable platform for the continuous flow photo-oxidation of cyclopentadien to the labile intermadiate 2,3-dioxabicyclo[2.2.1]hept-5-ene prior to its reduction to cyclopent-4-ene-1,3-diol with thiourea. Rose Bengal was used as sensitizer under green irradiaton in a capillary reactor for contacting with oxygen gas. A maximum throughtput of 6 g h-1 was achieved with this approach. This paper can be found in Org. Process Res. Dev., DOI: 10.1021/acs.oprd.0c00066.


ITEM OF INTEREST  -  Decatungstate as photocatalyst in flow for C(sp3)-H functionalizations of light hydrocarbons

28th September 2020

Noël et al. recently published their groundbreaking work on the C-H activation of hydrocarbons by hydrogen atom transfer with decatungstate as photocatalyst. From C1 (methane) to C4 (isobutane), efficient C-H activation was possible resulting in carbon-centered radicals for subsequent reactions with various olefinic acceptors like benzylidenemalononitrile or triethyl ethylenetricarboxylate. This paper can be found in Science, DOI: 10.1126/science.abb4688.


ITEM OF INTEREST  -  Hydrogen gas formation by consecutive charging of perylene dye sensitized Pt/TiO2

24th September 2020

Würthner, Xie et al. present their work on a photocatalytic system containing a perylene bisimide dye as a photosensitizer anchored to Pt-coated TiO2 nanoparticles via carboxyl groups. Consecutive light absorption in the green and IR region results in a stable perylene bisimide dianion with triethanolamine as sacrificial electron donor. The dianion itself absorbs in the red light region and injects electrons into the TiO2 nanoparticle for H2 generation at the Pt co-catalyst. This paper can be found in Angew. Chem. Int. Ed., DOI: 10.1002/ange.202001231.


ITEM OF INTEREST  -  Predicting the performance of photochemical reactions in flow

23rd September 2020

Sezen-Edmonds et al. recently published their methodology for predicting the performance of photochemical transformations for scale-up in different platforms. Beside high-throughput experiments, also computational modeling was applied to predict the conversion for a [2 + 2] photocycloaddition reaction and a photoredox-mediated decarboxylative intramolecular arene alkylation reaction. This paper can be found in Org. Process Res. Dev., DOI: 10.1021/acs.oprd.0c00182.


 

ITEM OF INTEREST  -  Tandem photoredox catalysis for complex amidation reactions with CO

22nd September 2020

Polyzos et al. report a new visible‐light‐mediated carbonylative amidation of aryl, heteroaryl, and alkyl halides. Here, consectutive multiphoton excitation of the Ir catalyst has been used to overcome the thermodynamic limitations of visible light photoredox catalysis to generate high energy photoreductants. With this approach, aryl bromides, iodides, and even chlorides as well as primary, secondary, and tertiary alkyl iodides have been converted to the desired amides. This paper can be found in Angew. Chem. Int. Ed., DOI: 10.1002/anie.202006720.


 

ITEM OF INTEREST  -  Characterization of Taylor flow in a photo microreactor

21st September 2020

Kuhn et al. present their recent work on photon transport and hydrodynamics in gas-liquid flows to optimze the performance of a taylor flow photo microreactor, but also to design improved multiphase flow photochemical systems. This paper can be found in ChemPhotoChem, DOI: 10.1002/cptc.202000065.


 

NEWS  -  Article published in Chemistry - A European Journal

19th May 2020

Flow photochemistry as a tool in organic synthesis.

Chem. Eur. J.2020, 26, Early View

The second part of our review on flow photochemistry has been published. Here, selected reaction classes in organic synthesis are reviewed, which benefit from going to photo flow.


 

NEWS  -  Article published in ChemPhotoChem

6th April 2020

Reactor technology concepts for flow photochemistry.

ChemPhotoChem, 2020, 4, 235-254

The first part of our review on flow photochemistry has been finally published. This review presents the current developments in reactor design for photochemistry and photocatalysis in flow.