Seleno/Thio-functionalized ipso-Annulation of N-Propiolyl-2-arylbenzimidazole to Construct Azaspiro[5,5]undecatrienones

Till date, the ipso-cyclization of propiolamides is limited to provide azaspiro[4,5]decatrienones. Herein, we present the first example of ipso-carbocyclization, leading to azaspiro[5,5]-undecatrienones from N-propiolyl-2-arylbenzimidazoles, involving both the radical-based and electrophilic reactions. This report establishes an access to a wide range of chalcogenated (SCN/SCF3/SePh) benzimidazo-fused azaspiro[5,5]undecatrienones in good yields.

Facile synthesis of benzazoles through biocatalytic cyclization and dehydrogenation employing catalase in water

The benzazoles are very important entities having immense biological activities, hence; the synthesis of benzazoles is one of the prime areas for synthetic chemists. In pursuit of sustainable protocol, herein an oxidative enzyme i.e. catalase mediated sustainable synthesis is presented. Catalase is a metalloenzyme which is essential for the breakdown of toxic hydrogen peroxide into water and oxygen inside the cell. Despite the higher activity and turnover number of catalase inside the cell, its activity outside the cell is unexplored. Therefore, to explore the hidden potential of catalase for catalyzing the organic transformations, here we reported a green and efficient method for synthesis of benzazoles by the cyclocondensation of o-aminothiophenol or o-phenylenediammine and various aryl aldehydes with ensuing dehydrogenation. This protocol is greener, sustainable and rapid with excellent yields of the products and in addition to this, the catalase demonstrates good functional group tolerance.

A one-pot synthesis of benzimidazoles via aerobic oxidative condensation of benzyl alcohols with o-phenylenediamines catalyzed by [MIMPs]+Cl-/NaNO2/TEMPO

The ionic liquid 1-methyl-3-(3-sulfopropyl)imidazolium chloride ([MIMPs]+Cl-) in combination with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium nitrite (NaNO2) as a catalytic system demonstrates high efficiency in the one-pot two-step aerobic oxidative condensation of benzyl alcohols with 1,2-phenylenediamines to give benzimidazoles. Various benzimidazoles are obtained in good to excellent yields by this strategy.

A novel synthesis of 2-arylbenzimidazoles in molecular sieves-MeOH system and their antitubercular activity

Arylbenzimidazoles have been synthesized as antimycobacterial agents. An efficient synthesis has been developed for 2-arylbenzimidazoles from o-phenylenediamines and aromatic aldehydes in molecular sieves-methanol system. The methodology is straightforward to get 2-arylbenzimidazoles (3a-3z) in excellent yields with high chemoselectivity over 2-aryl-1-benzylbenzimidazoles (4a-4z). All these benzimidazole analogues were evaluated against M. tuberculosis in BACTEC radiometric assay. The compounds 4y and 4z exhibited potential antitubercular activity against M. tuberculosis H₃₇R_V, MIC at 16 µM and 24 µM respectively. The best compound of the series i.e. compound 4y was well tolerated by Swiss-albino mice in acute oral toxicity. Compound 4y possessing a diarylbenzimidazole core, can further be optimized for better activity.

The synthesis of benzimidazoles via a recycled palladium catalysed hydrogen transfer under mild conditions

An efficient synthesis of benzimidazoles was developed by virtue of a recycled palladium catalyzed hydrogen transfer.

Selective C–H trifluoromethylation of benzimidazoles through photoredox catalysis

This protocol presented a new strategy for visible light induced C–H trifluoromethylation at the C₄ of benzimidazoles using Togni's reagent in the presence of fac-Ir(ppy)₃.

One-pot strategy of copper-catalyzed synthesis of 1,2-disubstituted benzimidazoles

A simple, one-pot and copper-catalyzed coupling reaction for the construction of 1,2-disubstituted benzimidazole derivatives is described. A low-cost copper salt and a weak base, K₃PO₄, were utilized in this reaction. A variety of 1,2-disubstituted benzimidazoles were obtained in moderate to excellent yields.