A novel class of diazonium salts is introduced for the photochemical aryl-aryl coupling to produce (substituted) biphenyls. As common diazonium tetrafluoroborate salts fail, soluble and safe aryl diazonium trifluoroacetates are applied. In this mild synthesis route no catalysts are required to generate an aryl-radical by irradiation with UV-A light (365 nm). This reactive species undergoes direct C-H arylation at an arene, forming the product in reasonable reaction times. With the implementation of a continuous flow setup in a capillary photoreactor 13 different biphenyl derivatives are successfully synthesized. By integrating an inline F-NMR benchtop spectrometer, samples are reliably quantified as the fluorine-substituents act as a probe. Here, real-time NMR spectroscopy is a perfect tool to monitor the continuously operated system, which produces fine chemicals of industrial relevance even in a multigram scale.
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http://dx.doi.org/10.1002/chem.202303692 | DOI Listing |
Chemistry
May 2024
Division Chemistry, Sustainable Chemical Syntheses Group, Fraunhofer Institute for Microengineering and Microsystems IMM, Carl-Zeiss-Strasse 18-20, 55129, Mainz, Germany.
A novel class of diazonium salts is introduced for the photochemical aryl-aryl coupling to produce (substituted) biphenyls. As common diazonium tetrafluoroborate salts fail, soluble and safe aryl diazonium trifluoroacetates are applied. In this mild synthesis route no catalysts are required to generate an aryl-radical by irradiation with UV-A light (365 nm).
View Article and Find Full Text PDFACS Omega
December 2022
Department of Chemistry, Faculty of Sciences, Atatürk University, Erzurum25240, Türkiye.
Aggregation-induced emission (AIE) is an extraordinary photochemical phenomenon described by Tang's group in 2001, where the aggregation of some organic molecules enhances their light emission by limiting intramolecular activity in the aggregate state. This phenomenon offers new opportunities for researchers due to its potential applications in optoelectronics, energy, and biophysics. Tetraphenylethylenes (TPEs) are reliable AIE luminogens with a wide range of successful applications in material chemistry.
View Article and Find Full Text PDFChem Asian J
February 2022
Department of Chemistry, National Institute of Technology Srinagar, 190006, Srinagar, India.
An efficient photo-redox strategy for the aryl-aryl self-coupling of aryl halides through a heterogeneous catalysis route has been demonstrated. A coordinatively unsaturated Ni P surface with the enhanced photochemical property upon hetero-structuring with δ-MnO affects the organic transformation to biaryls with impressive yield and photo-conversion efficiency. The dual-role of the Ni P catalyst with its participation as the catalytic active surface and the photo-redox center distinguishes the organic transformation achieved herein with other catalytic and photocatalytic aryl-aryl self-coupling.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
June 2021
Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany.
Controlling the reactivity of carbene intermediates is a key parameter in the development of selective carbene transfer reactions and is usually achieved by metal complexes via singlet metal-carbene intermediates. In this combined experimental and computational studies, we show that the reactivity of free diaryl carbenes can be controlled by the electronic properties of the substituents without the need of external additives. The introduction of electron-donating and -withdrawing groups results in a significant perturbation of singlet triplet energy splitting of the diaryl carbene intermediate and of activation energies of consecutive carbene transfer reactions.
View Article and Find Full Text PDFJ Am Chem Soc
September 2019
Department of Chemistry , University of Basel, St. Johanns-Ring 19 , 4056 Basel , Switzerland.
Newly discovered tris(diisocyanide)molybdenum(0) complexes are Earth-abundant isoelectronic analogues of the well-known class of [Ru(α-diimine)] compounds with long-lived MLCT (metal-to-ligand charge transfer) excited states that lead to rich photophysics and photochemistry. Depending on ligand design, luminescence quantum yields up to 0.20 and microsecond excited state lifetimes are achieved in solution at room temperature, both significantly better than those for [Ru(2,2'-bipyridine)].
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