Metal-free, base catalyzed oxidative amination and denitration reaction: Regioselective synthesis of 3-arylimidazo[1,2-a]pyridines

doi:10.1016/j.tetlet.2018.08.024

Tetrahedron Letters

Volume 59, Issue 38, 19 September 2018, Pages 3485-3489

https://doi.org/10.1016/j.tetlet.2018.08.024 Get rights and content

Highlights

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First metal free system for synthesis of 3-phenylimidazo[1,2-a]pyridine.
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Can be performed at room temperature, unlike other reported strategies.
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Inexpensive base – Et₃N and H₂O₂ (30% aq.) as oxidant were used.
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Substrate scope includes substituted β-nitrostyrenes and 2-aminopyridines.

Abstract

A metal-free, regioselective strategy for the synthesis of 3-arylimidazo[1,2-a]pyridines from β-nitrostyrenes and 2-aminopyridines using triethylamine as the catalyst and H₂O₂ (30% aq.) as the oxidant is reported. The use of an inexpensive base and facile reaction conditions make this strategy a practical alternative for the synthesis of 3-arylimidazo[1,2-a]pyridines.

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Acknowledgements

Financial support from Dept. of Science and technology, DST, New Delhi for the award of Extramural research grant (no. EMR/2016/002485/OC) is gratefully acknowledged.

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We have developed a direct method for the synthesis of polyring-fused imidazo[1,2-a]pyridines via a copper-catalyzed annulation of electrophilic benzannulated heterocycles with 2-aminopyridine and 2-aminoquinoline. From 3-nitroindoles and 2-aminopyridine, we could synthesize tetracenes, viz., indole-fused imidazo[1,2-a]pyridines, and by starting from 2-aminoquinoline, we could generate pentacenes, viz., indolo-imidazo[1,2-a]quinolines. In addition, we could also extend the methodology toward the synthesis of benzothieno-imidazo[1,2-a]pyridines starting from 3-nitrobenzothiophene. Furthermore, the basic photophysical properties of these synthesized heteroacenes were evaluated.
Synthesis of Highly Functionalized Imidazopyridine: A Simple One-Pot Three-Component Synthesis of 6-Hydroxy-5 -(3-Phenylimidazo[1,2-a]Pyridin-2-yl)-2-Thioxo-2, 3-Dihydropyrimidin-4(1H)-Ones
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Metal-free, base catalyzed oxidative amination and denitration reaction: Regioselective synthesis of 3-arylimidazo[1,2-a]pyridines

Highlights

Abstract

Graphical abstract

Section snippets

Acknowledgements

Synthesis

Tetrahedron Lett.

Pestic. Sci.

Org. Biomol. Chem.

J. Org. Chem.

Synlett.

RSC Adv.

Org. Lett.

RSC Adv.

New J. Chem.

Adv. Biochem. Psychopharmacol.

CNS Drugs

Cardiovasc. Drug Rev.

Cerebrovasc. Dis.

J. Org. Chem.

Angew. Chem. Int. Ed.

Chem. Commun.

Bioorg. Med. Chem. Lett.