Synthesis of 1,2-Disubstituted Benzimidazoles by a Cu-Catalyzed Cascade Aryl Amination/Condensation Process

PTSA-catalyzed selective synthesis and antibacterial evaluation of 1,2-disubstituted benzimidazoles

Herein, we developed a convenient and efficient method via protonation of p-toluenesulfonic acid promoted cyclocondensation of o-phenylenediamine and aldehydes for selectively synthesizing 1,2-disubstituted benzimidazoles. This method displayed broad substrate adaptability and afforded the desired products in moderate to excellent yield in short reaction time. The effect of different substituents on the yield was investigated by extending optimum reaction conditions, which was further confirmed by theoretical calculations. It suggested that the surface electrostatic potential of oxygen atom and nitrogen atom on the substrates played important role in the synthesis of 1,2-disubstituted benzimidazoles. Besides, the crystal structure of compound 2t in the orthorhombic space group P2(1)/c was presented. Also, the anti-mycolicibacterium smegmatis (MC2155) activity was evaluated using rifampicin as a positive control. The products (2a, 2b, 2c, 2i, 2j, 2k, 2m) showed good antibacterial activities which were comparable to rifampicin.

PIII /PV =O Catalyzed Cascade Synthesis of N-Functionalized Azaheterocycles

An organocatalytic method for the modular synthesis of diverse N-aryl and N-alkyl azaheterocycles (indoles, oxindoles, benzimidazoles, and quinoxalinediones) is reported. The method employs a small-ring organophosphorus-based catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide) and a hydrosilane reductant to drive the conversion of ortho-functionalized nitroarenes into azaheterocycles through sequential intermolecular reductive C-N cross coupling with boronic acids, followed by intramolecular cyclization. This method enables the rapid construction of azaheterocycles from readily available building blocks, including a regiospecific approach to N-substituted benzimidazoles and quinoxalinediones.

Iridium(III)-Catalyzed Synthesis of Benzimidazoles via C-H Activation and Amidation of Aniline Derivatives

Ir(III)-catalyzed synthesis of benzimidazoles has been realized under redox-neutral conditions by annulation of aniline derivatives with dioxazolones. The reaction proceeded via a C-H activation-amidation-cyclization pathway with a decent substrate scope.

A bioinspired catalytic aerobic oxidative C-H functionalization of primary aliphatic amines: synthesis of 1,2-disubstituted benzimidazoles

Aerobic oxidative CH functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems.

Cascade palladium catalysis: a predictable and selectable regiocontrolled synthesis of N-arylbenzimidazoles

By choice: The palladium-catalyzed cascade reaction of 2-chloroaryl sulfonates with arylamine and amide nucleophiles provides direct access to N-arylbenzimidazoles. This strategy selectively produces the heterocycles based on chemoselective oxidative addition. 2-Chloroaryl triflates (Tf) produce one regioisomer and the corresponding 2-chloroaryl mesylates (Ms) deliver the other in a selectable manner.

Synthesis of benzimidazoles by PIDA-promoted direct C(sp2)-H imidation of N-arylamidines

A metal-free synthesis of diversified benzimidazoles from N-arylamidines through a phenyliodine(III) diacetate (PIDA) promoted intramolecular direct C(sp(2))-H imidation has been developed. The reaction proceeds smoothly at 0 °C or ambient temperature to provide the desired products in good to excellent yields. The synthesis of 2-alkyl- or 2-alkyl-fused benzimidazoles, which are generally inaccessible by similar Pd- or Cu-catalyzed approaches, can also be achieved.