Thianthrene Radical Cation as a TransientSETMediator: Photoinduced Thiocyanation and Selenocyanation of Arylthianthrenium Salts^†

Abstract

A novel transient SET mediator approach has been developed for the photoinduced radical-radical cross coupling reaction. Using the in-situ generated thianthrene radical cation as the transient SET mediator, the thiocyanation and selenocyanation of aryl thianthrenium salts have been realized under the mild conditions in the absence of the photocatalyst or single electron donor. In comparison with the photocatalyst enabled process, the protocol features mild conditions, simple manipulation, a broad substrate scope, excellent functional group and heterocycle tolerance. Due to the feasible accessibility of aryl thianthrenium salts, this method has also been applied in the efficient synthesis of a bioactive molecule, and the late-stage functionalization of complex arenes.

Photo- and Cu-Mediated 11C Cyanation of (Hetero)Aryl Thianthrenium Salts

“…Under visible light irradiation and with Cu/1,10-phenanthroline and photoredox catalyst co-mediators (analogous to those of our ArI reactions), we obtained radiolabeled biphenyl [ 11 C]­2 in 88% radiochemical conversion as determined by radio-TLC (RCC) (Table , entry 2). Unexpectedly, we obtained a slightly higher RCC (92%) without the photocatalyst (entry 1) presumably due to Ar• formation either via an excited Cu/1,10-phenanthroline complex or by visible light-induced homolysis. − Control reactions without light or the copper mediator provided no radiochemical incorporation (entry 3 or 4, respectively). Additionally, no RCC was observed from a reaction mixture heated to 80 °C for 5 min in the absence of light, ruling out a thermal pathway (entry 5).…”

Nucleophilic Organocatalyst for Photochemical Carbon Radical Generation via SN2 Substitution

“…Although these strategies are powerful, these photoredox catalyzed reactions rely on the redox properties of the starting materials . On the other hand, the directly photoexcited substrate, such as Barton ester and xanthate, to generate radical via homolytic cleavage is also a useful strategy . But this method requires stoichiometric reagents prepared in advance.…”

Online Charge-Generation Derivatization by Electrochemical Radical Cations of Thianthrene: Mass Spectrometry Imaging of Estrogens in Biological Tissues

“…However, [TT] •+ was typically generated from the activation of thianthrene S -oxide (TTO) with trifluoroacetic anhydride (TFAA) under chemical conditions. Fortunately, TT has a low oxidation potential ( E TT •+ / TT = 0.99 V vs Fc + /Fc), , and using the electrochemical method to oxidize TT to [TT] •+ is possible, which could ensure the reliable conversion rate for online charge-generation derivatization reactions.…”