A Versatile Method for the Synthesis of Benzimidazoles from o-Nitroanilines and Aldehydes in One Step via a Reductive Cyclization

Abstract

B e n z i m i d a z o l e s i n O n e S t e p f r o m oN i t r o a n i l i n e s a n d A l d e h y d e s

Sodium Dithionite

“…20 Only monosubstituted benzimidazole was obtained in this procedure. Furthermore, this method was applied to the synthesis of imidazole-containing heterocyclic ring systems.…”

A Palladium‐Catalyzed Regiospecific Synthesis of N‐Aryl Benzimidazoles

“…[12] ortho-Nitroaniline can also be used in the place of the 1,2-diaminoarene under reducing conditions. [13] However, the preparation of N-1-substituted benzimidazoles using these methods depends on the availability of the requisite 1,2-diaminoarene or ortho-nitroaniline, which are oftentimes difficult to prepare. [14] Benzimidazoles unsubstituted at N-1 such as 1 are more accessible.…”

Direct conversion of alkyl halides into benzimidazoles using pyridine-N-oxide and 1,2-diaminobenzenes

“…Reductive cyclization of o-nitroarylamines with aldehydes using sodium dithionite 32,33 or formic acid, iron powder and NH4Cl 34 leads to benzimidazole derivatives. These procedures use a large amount of reducing agent which leads to waste at the end of the synthesis.…”