FeBr3-catalysed synthesis of 3-aroylimidazo[1,2-a]pyridine and 3,3′-(arylmethylene)bis(2-phenylimidazo[1,2-a]pyridines) derivatives from 2-arylimidazo[1,2-a]pyridines and aromatic aldehydes: an investigation about mechanistic insights

TL;DR

A new FeBr3-catalyzed method efficiently produces imidazo[1,2-a]pyridine derivatives under air or argon atmospheres.

Contribution

A novel FeBr3-catalyzed aerobic oxidative coupling method for synthesizing imidazo[1,2-a]pyridine derivatives is introduced.

Findings

FeBr3 catalyzes the synthesis of 3-aroylimidazo[1,2-a]pyridine derivatives under aerobic conditions.

Argon atmosphere leads to the formation of bis(2-phenylimidazo[1,2-a]pyridines) derivatives.

Oxygen is identified as the key oxidant in the catalytic process.

Abstract

In a new approach, a series of 3-aroylimidazo[1,2-a]pyridine derivatives were prepared in high yields. This approach revealed the direct Fe-catalyzed functionalization of imidazo[1,2-a]pyridine derivatives with aryl aldehydes via an aerobic oxidative cross-dehydrogenative coupling process. This transformation occurred in the presence of air, and FeBr3 served as a homogeneous Lewis catalyst. O2 was found to be the principal oxidant responsible for the method's success. Interestingly, when these reactions were carried out under an argon atmosphere, 3,3′-(arylmethylene)bis(2-phenylimidazo[1,2-a]pyridines) derivatives were prepared in good yields.

FeBr3-catalysed synthesis of either 3-aroylimidazo[1,2-a]pyridines or 3,3′-(arylmethylene)bis(2-phenylimidazo[1,2-a]pyridines) derivatives from the same starting materials such as 2-arylimidazo[1,2-a]pyridines and aromatic aldehydes were reported.

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