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Synlett 2006(1): 0109-0111  
DOI: 10.1055/s-2005-922771
LETTER
© Georg Thieme Verlag Stuttgart · New York

A New Method for the Synthesis of 2-Aryl-1H-benzimidazoles: Selenium-­Catalyzed Reductive N-Heterocyclization of Benzylidene(2-nitroaryl)amines with Carbon Monoxide

Yutaka Nishiyama*, Mayu Fujimoto, Noboru Sonoda*
Department of Applied Chemistry, Faculty of Engineering, Kansai University, Suita, Osaka 564-8680, Japan
Fax: +81(6)63394026; e-Mail: nishiya@pcku.kansai-u.ac.jp;
Further Information

Publication History

Received 8 August 2005
Publication Date:
16 December 2005 (online)

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Abstract

The treatment of benzylidene(2-nitroaryl)amines, prepared by the reaction of o-nitro aniline and benzaldehydes, with carbon monoxide in the presence of a catalytic amount of selenium under basic conditions, afforded 2-aryl-1H-benzimidazoles in ­moderate to good yields.

Key words

selenium - carbon monoxide - 2-aryl-1H-benzimidazole - benzylidene(2-nitroaryl)amine

    References and Notes

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4

We have recently reported the selenium-catalyzed reductive N-heterocyclization of 2-nitrostyrenes, [5] N-(2-nitro-benzoyl)amides, [6] or 2-nitrobenzyl alcohols [7] with carbon monoxide that produced indoles, 3,4-dihydroquinazolin-4-ones, or 1,4-dihydro-2H-3,1-benzoxazin-2-ones.

8

A typical procedure is as follows: in a 50 mL stainless steel autoclave were placed benzylidene(2-nitroaryl)amine (0.5 mmol), selenium (8 mg, 0.1 mmol), DBU (304 mg, 2 mmol), 1,4-dioxane (5 mL), MS 3 Å (0.3 g) and a magnetic stirring bar. The mixture was stirred under pressurized carbon monoxide (30 atm) at 120 °C for 3 h. After evacuation of the excess carbon monoxide at r.t., the deposited selenium and MS 3 Å were filtered off. DBU was removed by reduced distillation. The residual solution was purified by chromatography on neutral aluminum oxide (CHCl3 as eluent) to give the 2-aryl-1H-benzimidazoles.