title: An Aluminum Fluoride Complex with an Appended Ammonium Salt as an Exceptionally Active Cooperative Catalyst for the Asymmetric Carboxycyanation of Aldehydes.
abstract: Al-F bonds are among the most stable σ bonds known, exhibiting an even higher bond energy than Si-F bonds. Despite a stability advantage and a potentially high Lewis acidity of Al-F complexes, they have not been described as structurally defined catalysts for enantioselective reactions. We show that Al-F salen complexes with appended ammonium moieties give exceptional catalytic activity in asymmetric carboxycyanations. In addition to aromatic aldehydes, enal and aliphatic substrates are well accepted. Turnover numbers up to around 104were achieved, whereas with previous catalysts 101-102turnovers were typically attained. In contrast to Al-Me and Al-Cl salen complexes, the analogous Al-F species are remarkably stable towards air, water, and heat, and can be recovered unchanged after catalysis. They possess a considerably increased Lewis acidity as shown by DFT calculations.
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Daniel
authors.identifier: 0000-0003-3329-5637
authors.initials: D
authors.lastname: Brodbeck
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Florian
authors.identifier: 0000-0003-3038-0609
authors.initials: F
authors.lastname: Broghammer
authors.affiliation: Universität Stuttgart, Institut für Theoretische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Jan
authors.identifier: 0000-0002-1301-2612
authors.initials: J
authors.lastname: Meisner
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Julian
authors.identifier: 0000-0002-5115-0469
authors.initials: J
authors.lastname: Klepp
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Delphine
authors.identifier: 0000-0001-8843-2745
authors.initials: D
authors.lastname: Garnier
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Wolfgang
authors.identifier: 0000-0002-6522-4190
authors.initials: W
authors.lastname: Frey
authors.affiliation: Universität Stuttgart, Institut für Theoretische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Johannes
authors.identifier: 0000-0001-6178-7669
authors.initials: J
authors.lastname: Kästner
authors.affiliation: Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: René
authors.identifier: 0000-0002-6668-4017
authors.initials: R
authors.lastname: Peters
keywords: Al−F bond; cyanide; dual activation; ion pairs; phase transfer catalysis