Selective One-pot Synthesis of 2-Aryl-1-arylmethyl-1H-1,3-benzimidazoles in the Presence of Ammonium Persulfate and Their Antioxidant Activity.

Anti-oxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions. Benzimidazoles and their derivatives make up an important class of heterocyclic compounds which have a wide range of therapeutic and pharmacological properties, including anti-oxidant,[1] antimicrobial,[[2]] antihelmintic,[4] anticancer,[5] antihypertensive,[6] anti-inflammatory,[7] analgesic,[8] and antiprotozoal activities.[9] The classical synthesis of benzimidazoles involves the reaction between an I ortho i -phenylendiamine and a carboxylic acid (or derivative, such as a nitrile, amidate, or orthoester) under harsh dehydrating conditions.[10] A survey of the recent literature reveals several methods for the synthesis of benzimidazoles using sulfamic acid,[11] DDQ,[12] air,[13] Oxone,[14] FeCl SB 3 sb /Al SB 2 sb O SB 3 sb ,[15] In(OTf) SB 3 sb , [16] Yb(OTf) SB 3 sb ,[17] Sc(OTf) SB 3 sb ,[18] KHSO SB 4 sb ,[19] IL,[20] or PBBS.[21] Oxidation reactions can produce free radicals. Some of the compounds displayed moderate anti-oxidant activity using the DPPH radical assay. Several compounds from fruits and vegetables were recently found to possess anti-oxidant activities.[23] In this vein, heterocyclic compounds obtained by synthesis are also reported to possess anti-oxidant activity.[24] Benzimidazoles have been studied in this regard and are used, for example, as radical scavengers.[25] As part of our systematic research on synthesis methodology,[[26], [28], [30]] we now report a selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles in water and under solvent-free conditions. [Extracted from the article]