Visible‐Light‐Promoted Reversible Sulfide/Iodide Exchange in Fluoroalkyl Sulfides Enabled by Electron Donor‐Acceptor Complex Formation

Abstract

Catalyst-free visible-light-mediated exchange of two photoredox active groups, a 4-perfluoropyridinylthio group and an iodide group, attached to a fluorinated alkyl fragment is described. The reaction can be preparatively performed in both directions by appropriate choice of wavelength, solvent, and counterion. In the forward reaction, alkyl sulfide interacts with an iodide anion to give alkyl iodide and a thiolate anion, with the driving force provided by blue light (455 nm). In the backward process, fluorinated alkyl iodide interacts with the thiolate under violet light (400 nm). The reactions proceed through the formation of electron donor-acceptor (EDA) complexes, which were observed by UV/Vis absorption or NMR spectroscopies. Evidence of the sulfur-iodide interaction was supported by X-ray analysis.

Sulfones Bearing Perfluorinated Pyridine Group: Synthesis and Photocatalytic Reaction with α‐(Trifluoromethyl)styrenes

“…Recently, we studied the EDA complex in SPyf‐containing ammonium salt with iodide counterion [30b] . X‐Ray diffraction indicated a presence of a weak binding between sulfur atom and iodide anion.…”

Visible‐Light Promoted Radical Fluoroalkylation of O‐ and N‐Substituted Alkenes

“…Compounds 9 containing tetrafluoropyridine fragment (PyfS) constitute another class of reagents, which were successfully employed in photoredox reactions based on cleavage of the C−S bond [63–66] (Scheme 12). They are obtained by thiol‐ene addition to gem ‐difluorostyrenes catalyzed by 9‐phenylacrydine under irradiation [63] .…”

“…The primary products were not isolated, but were converted into 3-fluorofurans upon brief treatment of the reaction mixture with acid. [61] Compounds 9 containing tetrafluoropyridine fragment (PyfS) constitute another class of reagents, which were successfully employed in photoredox reactions based on cleavage of the CÀ S bond [63][64][65][66] (Scheme 12). They are obtained by thiol-ene addition to gem-difluorostyrenes catalyzed by 9phenylacrydine under irradiation.…”

Photo‐induced Desulfurative Processes for Carbon Radical Generation

“…[28][29][30][31] On the other hand, the desulfurization of the second class of thioethers (D or G) can be achieved by initial SET reduction of thioethers containing either tetra-fluoropyridine or thiazolium cores (Scheme 8B). [32][33][34][35][36][37][38][39][40] The splitting of the CÀ S bond in the radicals E or H then leads to the carbon radicals and either a stabilized thiolate F or the 3methylthiazolidine-2-thione J byproduct.…”

“…The use of fluorinated PyfS derivatives was then investigated in the visible‐light promoted desulfurative iodination (Scheme 15). [36] It was found that reaction of difluorinated thiol precursors 48 with an excess of LiI in DMF at 5 °C under blue LED irradiation afforded the corresponding iodides 49 in high yields. Monofluorinated thiol precursors could be transformed under violet light, whereas no reaction was observed for fluorine‐free alkyl groups.…”