title: Catalytic Synthesis of N-Heterocycles via Direct C(sp3)-H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand.
abstract: Coordination of FeCl3to the redox-active pyridine-aminophenol ligand NNOH2in the presence of base and under aerobic conditions generates FeCl2(NNOISQ) (1), featuring high-spin FeIIIand an NNOISQradical ligand. The complex has an overall S = 2 spin state, as deduced from experimental and computational data. The ligand-centered radical couples antiferromagnetically with the Fe center. Readily available, well-defined, and air-stable 1 catalyzes the challenging intramolecular direct C(sp3)-H amination of unactivated organic azides to generate a range of saturated N-heterocycles with the highest turnover number (TON) (1 mol% of 1, 12 h, TON = 62; 0.1 mol% of 1, 7 days, TON = 620) reported to date. The catalyst is easily recycled without noticeable loss of catalytic activity. A detailed kinetic study for C(sp3)-H amination of 1-azido-4-phenylbutane (S1) revealed zero order in the azide substrate and first order in both the catalyst and Boc2O. A cationic iron complex, generated from the neutral precatalyst upon reaction with Boc2O, is proposed as the catalytically active species.
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Bidraha
authors.initials: B
authors.lastname: Bagh
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Daniël L J
authors.initials: DLJ
authors.lastname: Broere
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Vivek
authors.initials: V
authors.lastname: Sinha
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Petrus F
authors.initials: PF
authors.lastname: Kuijpers
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Nicolaas P
authors.initials: NP
authors.lastname: van Leest
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Bas
authors.identifier: http://orcid.org/0000-0002-3482-7669
authors.initials: B
authors.lastname: de Bruin
authors.affiliation: Institüt für Anorganische Chemie, Georg-August-Universität Göttingen , Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Serhiy
authors.initials: S
authors.lastname: Demeshko
authors.affiliation: Small Molecule X-ray Crystallography, Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Maxime A
authors.initials: MA
authors.lastname: Siegler
authors.affiliation: Homogeneous, Bioinspired and Supramolecular Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Jarl Ivar
authors.identifier: http://orcid.org/0000-0003-0665-9239
authors.initials: JI
authors.lastname: van der Vlugt