C-H Functionalization of Imidazo[1,5-a]pyridines: A Metal-Free Approach for Methylene Insertion to Access
Shivangani Mahajan1,2, Sanghapal D Sawant1,3,2
1Natural Products and Medicinal Chemistry Division, CSIR-Indian Institute of Integrative Medicine, Jammu 180001, India.
Abstract:
Formaldehyde has been used as a solvent and a source of carbon to insert a methylene group for bridging two imidazo[1,5-a]pyridine molecules without using any metal catalysis. This strategy has been extended on other alkyl-, aryl-, and heteroaryl aldehydes as well. This C(sp2)-C(sp3)-H-C(sp2) bond forming reaction proceeds via C(sp2)H functionalization of imidazo[1,5-a]pyridine and was applied on a wide range of substrates offering moderate to good yields of methylene-bridged/inserted bis-imidazo[1,5-a]pyridines. Most importantly, as an application, the bis-heteroarene product has been demonstrated as a ligand. The ligand-like behavior of bis-imidazo[1,5-a]pyridines has been demonstrated as an extension of current methodology. This reaction works well at the gram scale level.
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