Synthesis of imidazo and benzimidazo[2,1-a]isoquinolines by rhodium-catalyzed intramolecular double C–H bond activation

Vutukuri Prakash Reddy,Takanori Iwasaki,Nobuaki Kambe

doi:10.1039/c3ob27396b

Vutukuri Prakash Reddy, Takanori Iwasaki + Show 1 more

Open Access

https://doi.org/10.1039/c3ob27396b

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Journal: Organic & Biomolecular Chemistry	Publication Date: Jan 1, 2013
Citations: 45	License type: cc-by

Affiliation: Osaka University

Abstract

The rhodium-catalyzed intramolecular direct arylation of imidazole and benzimidazole derivatives via double C-H bond activation is described. This approach provides new access to a wide range of imidazo and benzimidazo[2,1-a]isoquinoline derivatives in moderate to high yields. This reaction provides an alternative method to the known Pd-catalyzed intramolecular oxidative cross-coupling reactions.

Highlights

Since imidazo and benzimidazo[2,1-a]isoquinoline derivatives show interesting biological activities such as anticancer, anti-HIV-1, antimicrobial and antiviral properties,[3,4] a variety of synthetic protocols have been developed for the preparation of imidazo and benzimidazo[2,1-a]isoquinoline derivatives based on condensation reactions[5] and the photocyclization of 1-styrylimidazoles.[6]
Coupling reactions catalyzed by transition metals, such as palladium and copper, have recently been reported and successfully applied to the preparation of such heterocyclic compounds through C–N and C–C cross-coupling.[7]
As a promising strategy for the synthesis of the imidazo and benzimidazo[2,1-a]isoquinoline derivatives, the intramolecular oxidative cross-coupling via cleavage of two C–H bonds would be a more straightforward and efficient route to these compounds

Summary

Introduction

Nitrogen-containing heterocycles and their derivatives are often found in natural products and in pharmaceuticals and agrochemicals.[1,2] Since imidazo and benzimidazo[2,1-a]isoquinoline derivatives show interesting biological activities such as anticancer, anti-HIV-1, antimicrobial and antiviral properties,[3,4] a variety of synthetic protocols have been developed for the preparation of imidazo and benzimidazo[2,1-a]isoquinoline derivatives based on condensation reactions[5] and the photocyclization of 1-styrylimidazoles.[6]. This reaction provides an alternative method to the known Pd-catalyzed intramolecular oxidative cross-coupling reactions. As a promising strategy for the synthesis of the imidazo and benzimidazo[2,1-a]isoquinoline derivatives, the intramolecular oxidative cross-coupling via cleavage of two C–H bonds would be a more straightforward and efficient route to these compounds.

Results

Conclusion