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Imidazo[1,5‐ a ]pyridines – A Versatile Platform for Structurally Distinct N ‐Heterocyclic Olefins and π‐Extended Heterocycles

Year: 2025

Type: article

Abstract: The synthesis of polarized N-heterocyclic olefins (NHOs) based on an imidazo[1,5-a]pyridine scaffold is presented. In contrast to regular NHOs the unique bicyclic heterocyclic core allows the incorporation of various substituents in close proximity to the highly polarized exocyclic C─C bond. The donor properties of the new carbon-based ligand class were quantified and the coordination chemistry explored. Alkenyl or alkynyl groups at the C5-position lead to spontaneous cyclization to yield imidazo[2,1,5-de]quinolizines. The unique cyclization strategy was compatible with a wide range of substitution patterns and yields highly electron-rich π-delocalized heterocycles. The electronic structure of the novel partially antiaromatic heterocycle was thoroughly investigated. One-electron oxidation occurs at low potentials and lead to a stable monomeric radical-cation confirmed by XRD, which showed solution phase fluorescence expanding into the field of open-shell organic materials.

Source: Angewandte Chemie International Edition

DOI: 10.1002/anie.202506305