Cobalt(III)‐Catalyzed Intramolecular Cross‐Dehydrogenative C−H/X−H Coupling: Efficient Synthesis of Indoles and Benzofurans

Abstract

An efficient cobalt(III)-catalyzed intramolecular cross-dehydrogenative C-H/N-H coupling of ortho-alkenylanilines has been developed utilizing O as a terminal oxidant. The developed reaction tolerates various reactive functional groups and allows the synthesis of diverse indole derivatives in good to excellent yields. The method was successfully extended to the synthesis of benzofurans through the intramolecular cross-dehydrogenative C-H/O-H coupling of ortho-alkenylphenols.

Stereoselective and Regioselective Synthesis of Heterocycles via Copper-Catalyzed Additions of Amine Derivatives and Alcohols to Alkenes

“…78 A protocol for [Co]/[Cu] co-catalyzed aerobic oxidative cyclization of 2-vinyl anilines and phenols has also been reported. 79 …”

Divergent Functionalization of N‐Alkyl‐2‐alkenylanilines: Efficient Synthesis of Substituted Indoles and Quinolines

“…Based on the preliminary mechanistic investigation and literature precedence, a plausible mechanism for the divergent functionalization of ortho ‐alkenylanilines is proposed in Scheme . As shown in Scheme , rhodium‐catalyzed CDC of ortho ‐alkenylanilines starts with the generation of active rhodium species A through ligand exchange.…”

“…Recently, we demonstrated the CDC of C−H/N−H bonds of N‐alkylated ortho ‐alkenylanilines to N‐alkylated indole derivatives by employing a cobalt(III)‐based catalyst . Based on this study and our continued interest in the development of a novel methodology based on rhodium(III) catalysts and ortho ‐alkenylanilines, we envisioned the related rhodium(III)‐catalyzed CDC of C−H/N−H bonds of N‐alkylated ortho ‐alkenylanilines to compare the reactivity and efficiency.…”

“…Recently,w ed emonstratedt he CDC of CÀH/NÀHb onds of N-alkylated ortho-alkenylanilines to N-alkylated indole derivatives by employing ac obalt(III)-based catalyst. [8] Based on this study and our continuedi nteresti nt he development of a novel methodology based on rhodium(III) catalysts [10] and ortho-alkenylanilines, [9h, 11] we envisioned the related rhodium(III)-catalyzed CDC of CÀH/NÀHbonds of N-alkylated ortho-alkenylanilines to compare the reactivity and efficiency.I na ddition, the construction of the quinoline moiety was also anticipated through the oxidative cyclization [12] of N-alkylated orthoalkenylanilines (Scheme 1). It is important to note that oxidative CÀCb ond-forming cyclization of N-alkylated ortho-alkenylanilines is not yet documented.…”

Cobalt‐Catalyzed Annulation Reactions via C−H Bond Activation

“…Anbarasan and co‐workers achieved the intra‐molecular cross‐dehydrogenative coupling of 2‐alkenyl aniline 66 and 2‐alkenyl phenol derivatives 65 in the presence of CoCp*(CO)I 2 as a catalyst (Scheme ) . As yet, a common limitation of this CoCp* catalysis is the use of air (O 2 ) as a sole oxidant or terminal oxidant.…”