Co(acac)₂/O₂-Mediated Oxidative Isocyanide Insertion with 2-Aryl Anilines: Efficient Synthesis of 6-Amino Phenanthridine Derivatives

Abstract

A novel and efficient protocol for the creation of 6-amino phenanthridine derivatives by Co(acac)2-catalyzed isocyanide insertion with 2-aryl anilines under an O2 atmosphere via homolytic aromatic substitution (HAS) type C-H functionalization has been developed. This reaction not only proceeds smoothly utilizing O2 as the oxidant but also provides a new approach to construct phenanthridine derivatives utilizing readily available 2-aryl anilines with isocyanides instead of 2-isocyanobiaryls with different radical precursors.

Base Metal Catalyzed Isocyanide Insertions

“…[53] In 2014, Zhu et al devised an ovel approach to the construction of benzo-fused 2-aminoquinolines 98. [54] Under similar catalytic conditions as described in Scheme 23, acomplex of o-aminobiphenyls 97 and Co II X 2 undergoes deprotonation, isocyanide insertion, and one-electron oxidation to afford amidinoyl Co III species 99 (Scheme 25). Thea uthors proposed that subsequent homolysis of the cobalt-carbon bond in Co III species 99 furnishes amidinoyl radical 100,which undergoes an intramolecular homolytic aromatic substitution (HAS), affording the biologically valuable 6-aminophenantridines 98 in low to moderate yields.M olecular oxygen was used as the optimal oxidant.…”

Air stable pincer (CNC) N-heterocyclic carbene–cobalt complexes and their application as catalysts for C–N coupling reactions

“…Most synthetic chemists around the world have employed their palladium catalyst systems and it was only in the early 2000's that the first nickel catalysed amination reaction was reported [19a,b]. Transition metal catalytic systems containing cobalt are even rarer [10] and except for a few systems involving cobalt salts [21,39]; their application for activating C-N coupling reactions is scarce and to the best of our knowledge this is the first application of pincer NHC-Co complexes for C-N coupling reactions.…”

Cobalt‐Catalyzed Intermolecular Oxidative Isocyanide Insertion with Two Amines: An Approach to Guanidines

“…Based on the literature reports8,12–15 and the above results, a plausible mechanism is proposed in Scheme . First, the Co(II) salt may react with isocyanide 2 to give Co(II) complex A .…”