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Imidazolium Based Fluorous N‐Heterocyclic Carbenes as Effective and Recyclable Organocatalysts for Redox Esterification
Author(s) -
Červenková Šťastná Lucie,
Bílková Veronika,
Cézová Tereza,
Cuřínová Petra,
Karban Jindřich,
Čermák Jan,
Krupková Alena,
Strašák Tomáš
Publication year - 2020
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202000273
Subject(s) - chemistry , ionic liquid , catalysis , organocatalysis , umpolung , organic chemistry , alkyl , redox , iodide , combinatorial chemistry , enantioselective synthesis , nucleophile
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.