Chemoselective synthesis of 1,2-disubstituted benzimidazoles in lactic acid without additive

Lactic acid is recognised as a biocompatible medium for the chemoselective synthesis of the 1,2-disubstituted benzimidazole scaffold via a direct one-pot cyclocondensation of o-phenylenediamine with aldehydes. Various 1,2-disubstituted benzimidazole derivatives were successfully synthesised with high selectivity with good to excellent yields without any additional catalyst or additive. Most products could be isolated by a simple filtration after completion of the reactions. Satisfactory results were also obtained from multi-gram scale reactions. (c) 2016 Institute of Chemistry, Slovak Academy of Sciences