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Article

Radical C–H 18F-Difluoromethylation of Heteroarenes with [18F]Difluoromethyl Heteroaryl-Sulfones by Visible Light Photoredox Catalysis

1
GIGA-Cyclotron Research Centre In Vivo Imaging, University of Liège, 8 Allée du Six Août, Building B30, Sart Tilman, 4000 Liège, Belgium
2
Global Chemistry, UCB NewMedicines, UCB Biopharma SPRL, 1420 Braine-l’Alleud, Belgium
3
Center for Integrated Technology and Organic Synthesis, Research Unit MolSys, University of Liège, (Sart Tilman), B-4000 Liège, Belgium
*
Authors to whom correspondence should be addressed.
The authors contributed equally to this work.
Catalysts 2020, 10(3), 275; https://doi.org/10.3390/catal10030275
Received: 5 February 2020 / Revised: 18 February 2020 / Accepted: 21 February 2020 / Published: 1 March 2020
The 18F-labeling of CF2H groups has been recently studied in radiopharmaceutical chemistry owing to the favorable nuclear and physical characteristics of the radioisotope 18F for positron emission tomography (PET). Following up on the reported efficiency of the [18F]difluoromethyl benzothiazolyl-sulfone ([18F]1) as a 18F-difluoromethylating reagent, we investigated the influence of structurally-related [18F]difluoromethyl heteroaryl-sulfones in the reactivity toward the photoredox C–H 18F-difluoromethylation of heteroarenes under continuous-flow conditions. In the present work, six new [18F]difluoromethyl heteroaryl-sulfones [18F]5a[18F]5f were prepared and, based on the overall radiochemical yields (RCYs), three of these reagents ([18F]5a, [18F]5c, and [18F]5f) were selected for the fully automated radiosynthesis on a FASTlabTM synthesizer (GE Healthcare) at high level of starting radioactivity. Subsequently, their efficiency as 18F-difluoromethylating reagents was evaluated using the antiherpetic drug acyclovir as a model substrate. Our results showed that the introduction of molecular modifications in the structure of [18F]1 influenced the amount of fac-IrIII(ppy)3 and the residence time needed to ensure a complete C–H 18F-difluoromethylation process. The photocatalytic C–H 18F-difluoromethylation reaction with the reagents [18F]5a, [18F]5c, and [18F]5f was extended to other heteroarenes. Radical-trapping experiments demonstrated the likely involvement of radical species in the C–H 18F-difluoromethylation process. View Full-Text
Keywords: fluorine-18; difluoromethylation; heteroarenes; visible light; photocatalysis fluorine-18; difluoromethylation; heteroarenes; visible light; photocatalysis
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MDPI and ACS Style

Lemos, A.L.P.; Trump, L.; Lallemand, B.; Pasau, P.; Mercier, J.; Lemaire, C.; Monbaliu, J.-C.; Genicot, C.; Luxen, A. Radical C–H 18F-Difluoromethylation of Heteroarenes with [18F]Difluoromethyl Heteroaryl-Sulfones by Visible Light Photoredox Catalysis. Catalysts 2020, 10, 275. https://doi.org/10.3390/catal10030275

AMA Style

Lemos ALP, Trump L, Lallemand B, Pasau P, Mercier J, Lemaire C, Monbaliu J-C, Genicot C, Luxen A. Radical C–H 18F-Difluoromethylation of Heteroarenes with [18F]Difluoromethyl Heteroaryl-Sulfones by Visible Light Photoredox Catalysis. Catalysts. 2020; 10(3):275. https://doi.org/10.3390/catal10030275

Chicago/Turabian Style

Lemos, Agostinho Luís Pereira, Laura Trump, Bénédicte Lallemand, Patrick Pasau, Joël Mercier, Christian Lemaire, Jean-Christophe Monbaliu, Christophe Genicot, and André Luxen. 2020. "Radical C–H 18F-Difluoromethylation of Heteroarenes with [18F]Difluoromethyl Heteroaryl-Sulfones by Visible Light Photoredox Catalysis" Catalysts 10, no. 3: 275. https://doi.org/10.3390/catal10030275

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