Heteropolyacids as heterogeneous and recyclable catalysts for the synthesis of benzimidazoles

Indion 190 resin: efficient, environmentally friendly, and reusable catalyst for synthesis of benzimidazoles, benzoxazoles, and benzothiazoles

“…A number of methods are in vogue for the synthesis of these heterocycles by using different catalysts such as Pd-catalyzed oxidative cyclization (12); ionic-liquid-mediated synthesis (13); baseassisted reaction of 1,1-dibromoethanes (14), SiO 2 / ZnCl 2 (15), ZrOCl 2 ×8H 2 O (16), In(OTF) 3 (17), polyethylene-glycol-mediated catalysts (18), and different heteropolyacid catalysts (19), which include condensation of orthoesters 20Á22, nitriles (23), aldehydes (24), carboxylic acids (25), acid chlorides (26), amides (27), and esters (28) with o-substituted aminoaromatics in the presence of different acids or catalysts; Beckmann rearrangement of o-acylphenol oximes (29); photocyclization of phenolic Schiff bases (30); and benzimidazole synthesis in solvent-free conditions (15). More recently, Germin et al (31) have developed cleaner protocols for alkoxybenzimidazole synthesis via S N Ar reaction, and our group developed benzimidazole, benzoxazole, and benzothiazole from condensation of aldehydes with o-substituted aminoaromatics in the presence of phosphorus trichloride (32).…”

Syntheses of Coumarins in Environmentally Friendly Ionics Liquids

“…2). A close comparison of these structures reveals highly superior impact of the ILs that are based on 2-aminoethanol (1) by comparison with more substituted other (2-hydroxyethyl)ammonium carboxylate (2,3). It allows assuming that primary aminogroup of ILs (1) possibly interacts with aromatic aldehyde group and so activates it.…”

“…A large number of natural products contain coumarin cycle. Coumarins are successfully used for preparation of different materials-optical brighteners [2,3], chromophoric compounds [4][5][6], etc.. They are also widely used in biological and medicinal research, and especially coumarin-3-carboxylic acid and other 3-substituted coumarins.…”

Synthesis of 2-Substituted Benzimidazoles and 1,5- Disubstituted Benzodiazepines Using Alum

“…Catalytic activities of different Lewis acids have been investigated in the synthesis of benzimidazole and benzodiazepines by different groups highlighting the advantages of their protocol over the other methods. [12][13][14][15][16][17][18] However, to the best of our knowledge no attempt has been made to correlate the surface properties of the catalysts and their catalytic activity in the condensation of aldehydes/ketones with OPDA to synthesizes benzimidazole and benzodiazepines Metal oxides and supported metal oxides are known to possess surface acidity and/or basicity and activate a number of industrially important organic transformations. [19][20][21][22][23][24] We have developed new method of synthesis of benzimidazole using green approach and alum as catalyst.…”