Visible light promoted PANI@Au:CuO catalyzed sequential amination, azidation and annulation for the preparation of 2-arylbenzimidazoles

Abstract

A protocol describing PANI@Au:CuO photocatalyzed sequential amination/azidation/annulation reactions to prepare 2-aryl benzimidazole derivatives has been developed.

Photochemical Synthesis of Benzimidazoles from Diamines and Aldehydes

“…In 2017, Luo and coworkers synthesized benzimidazoles from primary amines with molecular oxygen as the oxidant (Scheme 2, D ) [17] . In a similar manner, an efficient copper‐catalyzed strategy for the amination of methyl arenes using aniline, TMSN 3 and heating has been reported for the preparation of functionalized benzimidazoles, [18] while an oxidant‐free copper‐based photocatalytic system that utilizes Cu 2 O‐Fe 2 O 3 nanoparticles (NPs) for the construction of C–N bonds was developed by Bhalla (Scheme 2, E ) [19] . Recently, Li and coworkers utilized an organic dye, fluorescein, as the photocatalyst to synthesize benzimidazoles via Blue LED irradiation (Scheme 2, F ) [20] .…”

“…[17] In a similar manner, an efficient copper-catalyzed strategy for the amination of methyl arenes using aniline, TMSN 3 and heating has been reported for the preparation of functionalized benzimidazoles, [18] while an oxidant-free copper-based photocatalytic system that utilizes Cu 2 O-Fe 2 O 3 nanoparticles (NPs) for the construction of C-N bonds was developed by Bhalla (Scheme 2, E). [19] Recently, Li and coworkers utilized an organic dye, fluorescein, as the photocatalyst to synthesize benzimidazoles via Blue LED irradiation (Scheme 2, F). [20] Photochemistry has provided interesting approaches for the synthesis of benzimidazoles from diamines and aldehydes, either employing tetrazines, [21] or heterogeneous photocatalytic systems.…”

N-Radical enabled cyclization of 1,n-enynes

“…Azidation has attracted considerable attention because of the great importance of organic azides in drug discovery, chemical biology, and materials science [102][103][104][105][106]. Strategies for organic azides syntheses typically include SN2 reactions of alkyl halides, metal-catalyzed cross coupling, and azidation of alkenes or alkynes [107][108][109][110][111][112][113][114][115][116][117]. Among them, azidation provides a simple and atom economic method with suitable functional group compatibility, especially the well-developed N3 radical addition to unsaturated 1,n-enynes.…”

Gold‐Catalyzed Amination Reactions: Progress and Prospects

“…prepared PANI@Au:CuO nanocomposites, as catalyst for the synthesis of 2‐arylbenzimidazole derivatives via sequential amination, azidation and annulation reactions under mild conditions (Scheme 22). [43] In this protocol assemblies of the pentacenequinone derivative act as visible light harvesting materials as well as oxidants in multiple C−N bond formation reactions. They carried out the model reaction using toluene, aniline and TMSN 3 as azide source and identified the optimum condition as 1 mol% of PANI‐5@Au.CuO NCS as catalyst in DMSO under visible light irradiation.…”