Pyridinium-Derived Mesoionic N-Heterocyclic Olefins (py-mNHOs).

Mesoionic polarization allows access to electron-rich olefins that have found application as organocatalysts, ligands, or nucleophiles. Herein, we report the synthesis and characterization of a series of 3-methylpyridinium-derived mesoionic olefins (py-mNHOs). We used a DFT-supported design concept, which showed that the introduction of aryl groups in the 1-, 2-, 4-, and 6-positions of the heterocyclic core allowed the kinetic stabilization of the novel mesoionic compounds. Tolman electronic parameters indicate that py-mNHOs are remarkably strong σ-donor ligands toward transition metals and main group Lewis acids. Additionally, they are among the strongest nucleophiles on the Mayr reactivity scale. In reactions of py-mNHOs with electron-poor π-systems, a gradual transition from the formation of zwitterionic adducts via stepwise to concerted 1,3-dipolar cycloadditions was observed experimentally and analyzed by quantum-chemical calculations. © 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Citation

Qiu Sun, Andreas Eitzinger, Robin Esken, Patrick W Antoni, Robert J Mayer, Armin R Ofial, Max M Hansmann. Pyridinium-Derived Mesoionic N-Heterocyclic Olefins (py-mNHOs). Angewandte Chemie (International ed. in English). 2024 Mar 04;63(10):e202318283

PMID: 38153170

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