Imidazolium Based Fluorous N-Heterocyclic Carbenes as Effective and Recyclable Organocatalysts for Redox Esterification

0524181 - ÚCHP 2021 RIV DE eng J - Journal Article
Červenková Šťastná, Lucie - Bílková, Veronika - Cézová, T. - Cuřínová, Petra - Karban, Jindřich - Čermák, Jan - Krupková, Alena - Strašák, Tomáš
Imidazolium Based Fluorous N-Heterocyclic Carbenes as Effective and Recyclable Organocatalysts for Redox Esterification.
European Journal of Organic Chemistry. Roč. 2020, č. 24 (2020), s. 3591-3598. ISSN 1434-193X. E-ISSN 1099-0690
Institutional support: RVO:67985858
Keywords : fluorous ionic liquids * N-heterocyclic carbenes * organocatalysis
OECD category: Organic chemistry
Impact factor: 3.021, year: 2020
Method of publishing: Limited access

A series of new highly fluorophilic ionic liquids ( f > 110) was synthetized from 3‑iodopropyltris(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)silane and N‐alkyl imidazoles, followed by anion exchange. N‐heterocyclic carbenes generated in situ from obtained imidazolium salts were employed to catalyze redox esterification ( umpolung ) of cinnamaldehyde with alcohols. The most effective N‐methyl derivative with iodide as a counter anion was studied in detail with respect to the optimization of reaction conditions, substrate scope and recyclability. Recovery of the precatalyst was achieved using either fluorous extraction or performing the reaction in suitable fluorous biphase system with direct recycling of the fluorinated precatalyst phase. For both tested options, the catalytic activity did not significantly decrease within 5 subsequent cycles. The redox esterification was shown to proceed also in supercritical carbon dioxide (scCO 2 ) as an alternative solvent where the activity of the fluorinated catalyst was also superior to the nonfluorinated model, while retaining the benefit of easy recycling.
Permanent Link: http://hdl.handle.net/11104/0309759