Metal-free, regioselective, visible light activation of 4CzIPN for the arylation of 2H-indazole derivatives

Abstract

Highly regioselective organo photocatalysis of 4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene) for the arylation of 2H-indazole is demonstrated.

Visible light-induced functionalization of indazole and pyrazole: a recent update

“…3.2.2 C-3 arylation enabled by 4CzIPN as a photoredox catalyst. Very recently (in 2021), the Ramesh group 33 has reported a metal-free carbazole-based organophotocatalyzed arylation on 2H-indazole by coupling with substituted anilines. The reaction involved an in situ generation of aryl-diazonium salt followed by functionalization of 2H-indazoles 28.…”

“…The reaction was catalyzed by 4CzIPN in 7 W blue LED light in the presence of tert-butyl nitrite (tBuONO) in CH 3 CN solvent (Scheme 16). Under the optimized reaction conditions, the authors explored the scope of the reaction by varying aromatic amine derivatives (33). The aniline bearing either electronwithdrawing groups (e.g., -F, -Cl and -NO 2 ) or electron releasing groups (e.g.…”

C-3 Functionalization of 2-Aryl-2H-indazoles under Photo/Electrocatalysis

“…In 2021, Ramesh's group [36] reported a 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) catalyzed directly arylation of 2H-indazole (Scheme 7). Different from Kim's method [35] , more safe and easily available anilines were used as aryl radical sources.…”

Visible light-promoted, photocatalyst-free decarboxylative alkylation of 2H-indazoles via electron donor–acceptor complex activation

“…[8][9][10][11][12][13][14] Recently, visible light-promoted photoredox catalysis has been widely used in the direct functionalization of 2H-indazoles. [15][16][17][18][19][20][21][22] However, most of these protocols are highly dependent on precious transition metal complexes or synthetically elaborate organic dyes, featuring high manufacturing costs and inconveniences in eliminating the trace metal. Therefore, it is highly desirable to develop transition metal-free and traditional dye-free protocols to achieve the functionalization of 2H-indazoles.…”