Recyclable All-in-One Organo-Photo-Auxiliaries Enabling (sp3)C−(sp3)C Coupling Reactions with Diverse Functionalities

Abstract

Photochemical C−C coupling reactions can be tailored to industrial chemical processes and preparations of pharmaceuticals. Recent approaches in this area are limited to using precious transition metal coordination complexes that facilitate light absorption and redox processes with benchtop chemicals. Herein, we propose a paradigm that involves all-in-one organo-photo-auxiliaries, thio-heteroarenes, which exhibit unique photophysical properties. These thio-heteroarenes were employed to prepare several all-in-one ionic photo-salts from commercially available alkyl/benzyl and heterocyclic halides via aromaticity-mediated nucleophilic substitution reactions. From the library of >30 salts, we performed on-demand photochemical C−C coupling reactions to isolate numerous symmetrical and unsymmetrical diary/alkyl-ethanes with yields up to 84% and mass balance as high as 96%. We also investigated the influence of structural features/properties on the outcomes of the photochemical C−C coupling reactions. The current photochemical C−C method was successful in the isolation of >30 photoproducts, including the natural product Brittonin A, a precursor of Imipramine, and derivatives of the bioactive Honokiol Analogues. Furthermore, transient absorption spectroscopy and time-dependent density functional theory calculations were used to decipher the nature of light-promoted electronic transitions.