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Hydrogen Bonding Phase-Transfer Catalysis with Ionic Reactants: Enantioselective Synthesis of γ-Fluoroamines

[Image: see text] Ammonium salts are used as phase-transfer catalysts for fluorination with alkali metal fluorides. We now demonstrate that these organic salts, specifically azetidinium triflates, are suitable substrates for enantioselective ring opening with CsF and a chiral bis-urea catalyst. This...

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Detalles Bibliográficos
Autores principales: Roagna, Giulia, Ascough, David M. H., Ibba, Francesco, Vicini, Anna Chiara, Fontana, Alberto, Christensen, Kirsten E., Peschiulli, Aldo, Oehlrich, Daniel, Misale, Antonio, Trabanco, Andrés A., Paton, Robert S., Pupo, Gabriele, Gouverneur, Véronique
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2020
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441491/
https://www.ncbi.nlm.nih.gov/pubmed/32608977
http://dx.doi.org/10.1021/jacs.0c05131
Descripción
Sumario:[Image: see text] Ammonium salts are used as phase-transfer catalysts for fluorination with alkali metal fluorides. We now demonstrate that these organic salts, specifically azetidinium triflates, are suitable substrates for enantioselective ring opening with CsF and a chiral bis-urea catalyst. This process, which highlights the ability of hydrogen bonding phase-transfer catalysts to couple two ionic reactants, affords enantioenriched γ-fluoroamines in high yields. Mechanistic studies underline the role of the catalyst for phase-transfer, and computed transition state structures account for the enantioconvergence observed for mixtures of achiral azetidinium diastereomers. The N-substituents in the electrophile influence the reactivity, but the configuration at nitrogen is unimportant for the enantioselectivity.