Issue 19, 2022

A directing group switch in copper-catalyzed electrophilic C–H amination/migratory annulation cascade: divergent access to benzimidazolone/benzimidazole

Abstract

We present here a copper-catalyzed electrophilic ortho C–H amination of protected naphthylamines with N-(benzoyloxy)amines, cyclization with the pendant amide, and carbon to nitrogen 1,2-directing group migration cascade to access N,N-disubstituted 2-benzimidazolinones. Remarkably, this highly atom-economic tandem reaction proceeds through a C–H and C–C bond cleavage and three new C–N bond formations in a single operation. Intriguingly, the reaction cascade was altered by the subtle tuning of the directing group from picolinamide to thiopicolinamide furnishing 2-heteroaryl-imidazoles via the extrusion of hydrogen sulfide. This strategy provided a series of benzimidazolones and benzimidazoles in moderate to high yields with low catalyst loading (66 substrates with yields up to 99%). From the control experiments, it was observed that after the C–H amination an incipient tetrahedral oxyanion or thiolate intermediate is formed via an intramolecular attack of the primary amine to the amide/thioamide carbonyl. It undergoes either a 1,2-pyridyl shift with the retention of the carbonyl moiety or H2S elimination for scaffold diversification. Remarkably, inspite of a positive influence of copper in the reaction outcome, from our preliminary investigations, the benzimidazolone product was obtained in good to moderate yields in two steps under metal-free conditions. The N-pyridyl moiety of the benzimidazolone was removed for further manipulation of the free NH group.

Graphical abstract: A directing group switch in copper-catalyzed electrophilic C–H amination/migratory annulation cascade: divergent access to benzimidazolone/benzimidazole

Supplementary files

Article information

Article type
Edge Article
Submitted
10 Mar 2022
Accepted
13 Apr 2022
First published
14 Apr 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2022,13, 5726-5733

A directing group switch in copper-catalyzed electrophilic C–H amination/migratory annulation cascade: divergent access to benzimidazolone/benzimidazole

H. M. Begam, S. Nandi and R. Jana, Chem. Sci., 2022, 13, 5726 DOI: 10.1039/D2SC01420C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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