Abstract
Imidazo[1,5-a]pyridines were efficiently prepared via the cyclization of 2-picolylamines with nitroalkanes electrophilically activated in the presence of phosphorous acid in polyphosphoric acid (PPA) medium.
Highlights
It is hard to overstate the importance of imidazo[1,5-a]pyridines in modern organic and medicinal chemistry
Imidazo[1,5-a]pyridines were efficiently prepared via the cyclization of 2-picolylamines with nitroalkanes electrophilically activated in the presence of phosphorous acid in polyphosphoric acid (PPA) medium
It was discovered that the nucleophilic amines 3 can be successfully employed in this type of transformations as well, providing the amidinium intermediates 4, which are susceptible to a variety of subsequent cyclizations
Summary
It is hard to overstate the importance of imidazo[1,5-a]pyridines in modern organic and medicinal chemistry. Imidazo[1,5-a]pyridines were efficiently prepared via the cyclization of 2-picolylamines with nitroalkanes electrophilically activated in the presence of phosphorous acid in polyphosphoric acid (PPA) medium. We demonstrate a new synthetic approach towards imidazo[1,5a]pyridines, taking advantage of the unusual electrophilic properties of nitroalkanes activated by PPA. It was found that the reaction of 2-hydrazinylpyridine with electrophilically activated nitroalkanes provides the corresponding triazolopyridines 11 (Scheme 1) [47].
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