Construction of α-Amino Azines via Thianthrenation-Enabled Photocatalyzed Hydroarylation of Azine-Substituted Enamides with Arenes

Abstract

α-Amino azines are widely found in pharmaceuticals and ligands. Herein, we report a practical method for accessing this class of compounds via photocatalyzed hydroarylation of azine-substituted enamides with the in situ-generated aryl thianthrenium salts as the radical precursor. This reaction features a broad substrate scope, good functional group tolerance, and mild conditions and is suitable for the late-stage installation of α-amino azines in complex structures.

TEMPO-mediated late stage photochemical hydroxylation of biaryl sulfonium salts

“…At the initial stage of the investigation, biphenyl was chosen as a substrate to form aryl thianthrenium 18–24 salt 2a , which was utilized to explore the optimal conditions for a site-selective hydroxylation of simple arenes (Table 1). The type of light, power, additive, reaction time, solvent and hydroxyl sources were notably evaluated.…”

Palladium-Catalyzed Synthesis of Esters from Arenes through C–H Thianthrenation

“…Recently, the group of Ritter disclosed a C–H thianthrenation approach for obtaining versatile aryl-TT salts with exquisite site selectivity for further classic cross-coupling reactions . On the basis of this discovery, some other C–H bond functionalization involving hetero­(arylation), alkylation, trifluoromethylation, fluorination, borylation, oxygenation, and other functionalizations were realized by C–H thianthrenation of arenes. Herein, we report a palladium-catalyzed esterification of arenes with aryl formates under CO-free conditions mediated by regioselective C–H thianthrenation.…”

Cu-Mediated Thianthrenation and Phenoxathiination of Arylborons

“…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.…”

“…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.…”