N,N′-Diaryldihydrophenazines as Visible-Light Photocatalysts for Anilines’ Arylation Using a Dual Photoredox/Ni(II) Cross-Coupling Strategy

Abstract

It has been shown that cheap and easily available N,N′-diaryldihydrophenazines can successfully replace Ir(III)- and Ru(II)-based photocatalysts in the dual photoredox/Ni(II) C–N coupling of aryl halides with a wide range of anilines (32 examples). The efficient, operationally simple approach to diarylamines has been elaborated, which is amenable to scaling up via a flow apparatus.

Nickel Metallaphotoredox Buchwald–Hartwig Amination Reactions: A Perspective on Irradiation Light Wavelength

“…realized the cross‐coupling of aryl bromides and anilines at low Ni catalyst loading (0.5 mol %) by using two novel N , N ′‐ diaryldihydrophenazines ( OPC6 and OPC7 , Scheme 7). [45a] The variation of structures of two OPCs almost did not affect the catalytic efficiency, and electron‐poor aryl bromides showed much higher reactivity than that of electron‐rich substrates, which was consistent with previous reported results. It was proposed that the high reducing OPCs could facilitate the Ni(II)/Ni(0) reduction of precatalyst.…”

Synthesis of Diarylamines via Nitrosonium-Initiated C–N Bond Formation

“…Conventional cross-coupling reactions, including the palladium-catalyzed Buchwald–Hartwig reaction, copper-catalyzed Chan–Evans–Lam reaction, Ullmann-type reaction, and various cross coupling reactions facilitated by transition metal catalysts between arylamines and aryl halides/boronic acids, , are commonly employed for the synthesis of diarylamines (Scheme A). Recently, the merger of photoredox catalysis and transition metal catalysis has also been utilized to form C­(sp 2 )–N bonds . However, concerns arise from the use of costly and environmentally harmful transition metal catalysts in these coupling processes, along with the presence of their residual contaminants in the final products .…”

“…Recently, the merger of photoredox catalysis and transition metal catalysis has also been utilized to form C(sp 2 )–N bonds. 11 However, concerns arise from the use of costly and environmentally harmful transition metal catalysts in these coupling processes, along with the presence of their residual contaminants in the final products. 12 Alternative methods to synthesize diaryl amines include nucleophilic aromatic substitution (S N Ar) reactions, 13 the insertion of benzyne into amide, 14 coupling reactions between aryl boronic acid and hydroxylamines, 15 desulfinylative Smiles rearrangement, 16 hypervalent-iodine-mediated cross-amination, 17 and the reactions of nitrosoarenes with aryl boronic acids or 1,3,5-trimethoxybenzene ( Scheme 1 B).…”