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Published on: June 10, 2021
Synthesis of fused imidazo[1,2-a]pyridines derivatives through cascade C(sp2)-H functionalizations
Bin Li1, Nana Shen, Xinying Zhang
1School of Environment, School of Chemistry and Chemical Engineering, Henan Key Laboratory of Organic Functional Molecules and Drug Innovation, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, Collaborative Innovation Centre of Henan Province for Green Manufacturing of Fine Chemicals, Henan Normal University, Xinxiang, Henan 453007, P. R. China. libin@htu.edu.cn xuesen.fan@htu.cn.
Abstract:
An efficient and convenient synthesis of diversely substituted naphtho[1',2':4,5]imidazo[1,2-a]-pyridine derivatives from the cascade reactions of 2-arylimidazo[1,2-a]pyridines with a-diazo carbonyl compounds via Rh(iii)-catalyzed regioselective C(sp2)-H alkylation followed by intramolecular annulation is presented. Interestingly, when simple 2-arylimidazo[1,2-a]pyridines were used as the substrates, 5,6-disubstituted naphtho[1',2':4,5]imidazo[1,2-a]pyridines were efficiently obtained, whereas using 2-arylimidazo[1,2-a]pyridine-3-carbaldehydes as the substrates afforded naphtho[1',2':4,5]imidazo[1,2-a]-pyridine-5-carboxylates as the dominating products. Compared with literature methods for the synthesis of naphtho[1',2':4,5]imidazo[1,2-a]pyridine derivatives, the protocol presented herein has advantages such as easily obtainable substrates, simple operational procedure, high efficiency and excellent regio- and chemoselectivity.
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