Nitroarenes as versatile building blocks for the synthesis of unsymmetrical urea derivatives and N-Arylmethyl-2-substituted benzimidazoles

In this contribution, a fast and simple method for the synthesis of unsymmetrical urea derivatives and N-arylmethyl-2-substituted benzimidazoles was developed starting from nitroarenes. The reaction of nitroarenes and phenyl isocyanate or phenyl isothiocyanate in tin (II) chloride dihydrate/choline chloride eutectic mixture afforded the expected urea and thiourea derivatives, while the reaction of different aldehydes with o-nitroaniline or 4-methoxy-2-nitroaniline shows a markedly high preference for the obtention of N-arylmethyl-2-substituted benzimidazoles over the 2-substituted analogues. This method offers a straightforward alternative to obtain the target compounds in good to excellent yields with short reaction times employing an operationally simple experimental set-up. A series of unsymmetrical urea and thiourea derivatives together with 1,2-disubstituted benzimidazoles are easily obtained in good yields starting from nitroarenes employing the eutectic mixture tin (II) chloride dihydrate/choline chloride as reductive reaction media.