Access to 2-pyridinylamide and imidazopyridine from 2-fluoropyridine and amidine hydrochloride

Under catalyst-free conditions, an efficient method to synthesize 2-pyridinylamides has been developed, and the protocol uses inexpensive and readily available 2-fluoropyridine and amidine derivatives as the starting materials. Simultaneously, the copper-catalysed approach to imidazopyridine derivatives has been established with high chemoselectivity and regiospecificity. The results suggest that the nitrogen-heterocycles containing iodide substituents can also be compatible for the reaction via the cascade Ullmann-type coupling, and the nucleophilic substitution reaction provides the target products in a one-pot manner.

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.

Synthesis of benzimidazoles by CuI-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde in water

An efficient copper-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde for the synthesis of benzimidazoles with 1,10-phenanthroline as the ligand has been developed. A variety of substituted benzimidazole derivatives can be obtained in yields up to 95%.

Copper-catalyzed oxidative coupling reaction of α,β-unsaturated aldehydes with amidines: synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes

A convenient synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes was developed, which features high atom economy, cheap catalysts and mild conditions.

N–H⋯π induced configurational isomerism and the role of temperature in the Z to E isomerization of 2-fluoro-N′-(3-fluorophenyl)benzimidamide

The role of temperature in polymorphism and the isolation of configurational isomers of 2-fluoro-N′-(3-fluorophenyl)benzimidamide have been investigated.

Transition-metal-free synthesis of benzimidazoles mediated by KOH/DMSO

Benzimidazoles are prepared by intramolecular N-arylations of amidines mediated by potassium hydroxide in DMSO at 120 °C. In this manner, diversely substituted products have been obtained in moderate to very good yields.

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.

Aqueous synthesis of 1-H-2-substituted benzimidazoles via transition-metal-free intramolecular amination of aryl iodides

A straightforward method has been developed for the synthesis of the benzimidazole ring system through a carbon-nitrogen cross-coupling reaction. In the presence of 2.0 equiv. of K₂CO₃ in water at 100 °C for 30 h, the intramolecular cyclization of N-(2-iodoaryl)benzamidine provides benzimidazole derivatives in moderate to high yields. Remarkably, the procedure occurs exclusively in water and doesn’t require the use of any additional reagent/catalyst, rendering the methodology highly valuable from both environmental and economical points of view.

Palladium-catalyzed N-monoarylation of amidines and a one-pot synthesis of quinazoline derivatives

A method for the Pd-catalyzed N-arylation of both aryl and alkyl amidines with a wide range of aryl bromides, chlorides, and triflates is described. The reactions proceed in short reaction times and with excellent selectivity for monoarylation. A one-pot synthesis of quinazoline derivatives, via addition of an aldehyde to the crude reaction mixture following Pd-catalyzed N-arylation, is also demonstrated.

Application of the copper catalysed N-arylation of amidines in the synthesis of analogues of the chemical tool, blebbistatin

A robust protocol for the CuI-catalysed arylation of amidines is presented. Whilst the initially identified conditions were useful for benzamidine-derived substrates, difficulties were encountered with more complex substrates. This problem was overcome following a change in ligand type, enabling the synthesis of analogues of the chemical tool, blebbistatin.