Visible-Light-Induced, Base-Promoted Transition-Metal-Free Dehalogenation of Aryl Fluorides, Chlorides, Bromides, and Iodides

Abstract

We report a simple and efficient visible-light-induced transitionmetal-free hydrogenation of aryl halides. The combined visible light and base system is used to initiate the desired radical-mediated hydrogenation. A variety of aryl fluorides, chlorides, bromides, and iodides could be reduced to the corresponding (hetero)arenes with excellent yields under mild conditions. Various functional groups and other heterocyclic compounds are tolerated.

Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers

“…There are several photoredox transformations on unactivated organobromide and organochloride substrates that require UV excitation. [13][14][15][16][17] In addition, recent work from Jui's group demonstrated intramolecular hydroarylation reactions involving aryl bromide substrates, using visible light, an organic photosensitizer, and Hünig's base as the only reductant. 18 However, the vast majority of visiblelight photoredox transformations on unactivated organochloride or organobromide substrates require either additional energy input in the form of an applied potential or a second photon, or the use of additional costly additives beyond the sacricial reductant.…”

A Journey from June 2018 to October 2021 with N,N-Dimethylformamide and N,N-Dimethylacetamide as Reactants

“…Such a reactivity of DMF under t-BuOK conditions has been exploited for transition-metal-free Matsuda-Heck type reactions [75]. The association of t-BuOK, DMF, and visible-light irradiation mediated the dehalogenation of (hetero)aryl fluorides, chlorides, bromides, and iodides (Scheme 23a) [74], while the reductive cleavage of 4-methoxybenzenediazonium tetrafluoroborate occurred under light-free conditions (Scheme 23b) [75]. According to Qu/Kang's and Taillefer's teams [74,75], these reactions implicate the carbamoyl anion I 7 and, via electron transfer, the carbamoyl radical I 4 .…”

Metal‐Free Photoredox‐Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant

“…Concerning reduction of fluoroarenes, photoredox‐catalyzed partial HDF reactions and C−F functionalizations of polyfluoroarenes have been reported (Scheme 1b) [10] . However, HDF of monofluoroarene derivatives with photoredox systems remains undeveloped due to their inertness towards single‐electron‐transfer (SET), [11] while several methods utilizing photoirradiation have recently been developed, which involve direct photoexcitation of fluoroarenes [12a,b] and the use of stoichiometric amounts of strong photoreductants [12c,d] …”