A Versatile Method for the Synthesis of Benzimidazoles from o-Nitroanilines and Aldehydes in One Step via a Reductive Cyclization
Donglai Yang, Demosthenes Fokas*, Jingzhou Li, Libing Yu, Carmen M. Baldino
*Department of Chemistry, ArQule Inc, 19 Presidential Way, Woburn, MA 01801,
USA, Email: dfokas
arqule.com
D. Yang, D. Fokas, J. Li, L. Yu, C. M. Baldino, Synthesis, 2005, 47-56.
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Abstract
A highly efficient and versatile method for the synthesis of benzimidazoles was achieved in one step via the Na2S2O4 reduction of o-nitroanilines in the presence of aldehydes. Heating a solution of o-nitroaniline and an aldehyde in EtOH or another appropriate solvent, in the presence of aqueous or solid Na2S2O4, provided facile access to a series of 2-substituted N-H benzimidazoles containing a wide range of functional groups not always compatible with the existing synthetic methods. This methodology has also been applied to the regioselective synthesis of N-alkyl and N-aryl benzimidazoles and imidazole containing heterocyclic ring systems such as 1H-imidazo[4,5-b]pyridines and 1H-imidazo[4,5-f]quinoline.
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Key Words
benzimidazoles, reductive cyclization, sodium dithionite, imidazopyridines, imidazoquinolines
ID: J54-Y2005-600
