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Synthesis 2011(15): 2445-2453  
DOI: 10.1055/s-0030-1260106
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Imidazo[1,2-a]pyridines by the Bis(acetyloxy)(phenyl)-λ³-iodane-Mediated Oxidative Coupling of 2-Aminopyridines with β-Keto Esters and 1,3-Diones

Xianpei Wang, Lijuan Ma, Wei Yu*
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. of China
e-Mail: yuwei@lzu.edu.cn;
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Publikationsverlauf

Received 25 April 2011
Publikationsdatum:
14. Juli 2011 (online)

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Abstract

Imidazo[1,2-a]pyridine-3-carboxylates can be prepared directly from 2-aminopyridines and β-keto esters by using bis(acetyloxy)(phenyl)-λ³-iodane as an oxidant and boron trifluoride etherate as a catalyst. The amount of catalyst plays a key role in determining the course of the reaction. Whereas the use of 0.2 equivalents of catalyst ensures the generation of imidazo[1,2-a]pyridines, raising the amount of catalyst to 1.0 equivalents results in exclusive α-acetoxylation of the β-keto esters. 2-Aminopyridines can also react with 1,3-diones to afford 3-acylimidazo[1,2-a]pyridines.

Key words

heterocycles - polycycles - cyclization - oxidation - coupling

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