Oxidative Coupling of o-Phenylenediamine with Arylmethylamines to Synthesize Aryl-Substituted Benzimidazoles Under Catalyst-Free and Solvent-Free Conditions

Abstract

Solvent-free oxidative synthesis of benzimidazoles from arylmethylamines and o-phenylenediamine has been achieved under catalyst-free conditions. This reaction can use tert-butyl hydroperoxide (TBHP) as the oxidant, and a wide variety of derivatives were obtained in good yields. The reaction mechanism was proposed and this method provides a direct and practical approach for the preparation of substituted benzimidazoles.

GRAPHICAL ABSTRACT

Keywords:

• Benzimidazoles
• catalyst-free
• oxidation
• solvent-free
• TBHP

Notes

^a Reaction conditions: A mixture of o-phenylenediamine, benzylamine, and TBHP (70% in H₂O) was mixed in a three-necked flask, and then stirred rapidly for several hours. The reaction progress was monitored by TLC.

^b Isolated yield.

^a Reaction conditions: A mixture of 1 mmol diamine, 1.5 mmol aromatic amine, and 4 mmol TBHP (70% in H₂O) was mixed in a three-necked flask, and then stirred rapidiy at 100 °C for several hours. The reaction progress was monitored by TLC.

^b Isolated yield.