Insight into Regioselective Control in Aerobic Oxidative C–H/C–H Coupling for C3-Arylation of Benzothiophenes: Toward Structurally Nontraditional OLED Materials
Yang Shi, Ge Yang, Boming Shen, Yudong Yang, Lipeng Yan, Feng Yang, Jiahui Liu, Xingrong Liao, Peiyuan Yu, Zhengyang Bin, Jingsong You
Abstract
The installation of (benzo)thiophene-containing biaryls via coupling reactions has become a staple in designing photoelectric materials. Undeniably, C–H/C–H cross-coupling reactions between two (hetero)aromatics would be a shortcut toward these structural fragments. While more reliable cross-coupling technologies are well-established to provide C2-arylated (benzo)thiophenes, efficient methods that arylate the C3-position remain underdeveloped. Herein we provide insight into the factors that determine regioselectivity switching for these cross-coupling reactions. X-ray crystallographic analysis gives solid evidence for the key roles of triflate in regioselective dearomatization and acetate in base-assisted anti-β-deprotonated rearomatization. The first isolation and X-ray characterization of a medium-sized dearomatized cyclometalated adduct involving both substrates provide extra insight into aerobic oxidative Ar–H/Ar–H cross-coupling reactions. The mechanistic breakthrough incubates the first example, enabling C–H/C–H-type C3-arylation of benzothiophenes. Finally, this chemistry is used to design blue-emitting thermally activated delayed fluorescence (TADF) materials with a helicene conformation that exhibit a high maximum external quantum efficiency of 25.4% in OLED.