Sustainable Thioetherification via Electron Donor–Acceptor Photoactivation Using Thianthrenium Salts

Abstract

The synthesis of sulfides has been widely studied because this functional subunit is prevalent in biomolecules and pharmaceuticals, as well as being a useful synthetic platform for further elaboration. Thus, various methods to build CÀ S bonds have been developed, but typically they require the use of precious metals or harsh conditions. Electron donor-acceptor (EDA) complex photoactivation strategies have emerged as versatile and sustainable ways to achieve CÀ S bond formation, avoiding challenges associated with previous methods. This work describes an open-toair, photoinduced, site-selective CÀ H thioetherification from readily available reagents via EDA complex formation that tolerates a wide range of different functional groups. Moreover, C(sp 2 )À halogen bonds remain intact using this protocol, allowing late-stage installation of the sulfide motif in various bioactive scaffolds, while allowing yet further modification through more traditional CÀ X bond cleavage protocols. Additionally, various mechanistic investigations support the envisioned EDA complex scenario.

Photo-induced redox cascade reaction of nitroarenes and amines

“…1g, the black line). Based on these results, the photoactivation of nitroarenes 51,52 or the photoactivation of the [nitroarene-amine] electron donor-acceptor (EDA) complex [53][54][55][56][57][58][59] would be two possible ways for the initiation of the photoinduced reaction. However, the stoichiometric combination of 1a and 2a showed a basically identical UV-vis spectrum to that of 1a, and did not cause a bathochromic shift compared to the spectra of the individual components (Fig.…”

Selective C–S Bond Constructions Using Inorganic Sulfurs via Photoinduced Electron Donor–Acceptor Activation

“…The use of precious metals, strong bases, or high temperature is generally indispensable for these protocols. (b) Photoinduced C–S bond formation has become a powerful strategy for the development of aryl sulfide construction under mild conditions . However, most of these organic sulfuration agents need to be prepared in advance from inorganic sulfuration agents.…”

Cu-Mediated Thianthrenation and Phenoxathiination of Arylborons

“…In comparison with aryl halides and their analogues, the corresponding arylthianthrenium salts present unique reactivities in both transition metal catalyzed cross-coupling reactions as an aryl electrophile 23,[25][26][27][28][29][30][31][32] and photoredox catalyzed radical coupling reactions as an aryl radical precursor 24,[34][35][36][37][38][39][40] . Most importantly, several novel reaction processes with arylthianthrenium salts, including Pd-catalyzed tritiation 32 , photocatalyzed radical coupling, 24,[34][35][36][37][38][39][40] and electron donor-acceptor complex photoactivation 39,40 etc., have been proven to be inert or inefficient with aryl halides and their analogues. Accordingly, the direct functionalization of arenes via corresponding arylthianthrenium salts has become an appealing approach for the late-stage modification of drug molecules and bioactive molecules.…”

“…to the feasible accessibility of aryl sulfonium salts from simple arenes via regioselective electrophilic thianthrenation or phenoxathiination (Figure 1b) [22][23][24] . In comparison with aryl halides and their analogues, the corresponding arylthianthrenium salts present unique reactivities in both transition metal catalyzed cross-coupling reactions as an aryl electrophile 23,[25][26][27][28][29][30][31][32] and photoredox catalyzed radical coupling reactions as an aryl radical precursor 24,[34][35][36][37][38][39][40] . Most importantly, several novel reaction processes with arylthianthrenium salts, including Pd-catalyzed tritiation 32 , photocatalyzed radical coupling, 24,[34][35][36][37][38][39][40] and electron donor-acceptor complex photoactivation 39,40 etc., have been proven to be inert or inefficient with aryl halides and their analogues.…”