title: Lewis acid trapping of an elusive copper-tosylnitrene intermediate using scandium triflate.
abstract: High-valent copper-nitrene intermediates have long been proposed to play a role in copper-catalyzed aziridination and amination reactions. However, such intermediates have eluded detection for decades, preventing the unambiguous assignments of mechanisms. Moreover, the electronic structure of the proposed copper-nitrene intermediates has also been controversially discussed in the literature. These mechanistic questions and controversy have provided tremendous motivation to probe the accessibility and reactivity of Cu(III)-NR/Cu(II)N(•)R species. In this paper, we report a breakthrough in this field that was achieved by trapping a transient copper-tosylnitrene species, 3-Sc, in the presence of scandium triflate. The sufficient stability of 3-Sc at -90 °C enabled its characterization with optical, resonance Raman, NMR, and X-ray absorption near-edge spectroscopies, which helped to establish its electronic structure as Cu(II)N(•)Ts (Ts = tosyl group) and not Cu(III)NTs. 3-Sc can initiate tosylamination of cyclohexane, thereby suggesting Cu(II)N(•)Ts cores as viable reactants in oxidation catalysis.
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, D-12489 Berlin, Germany.
authors.forename: Subrata
authors.initials: S
authors.lastname: Kundu
authors.forename: Enrico
authors.initials: E
authors.lastname: Miceli
authors.forename: Erik
authors.initials: E
authors.lastname: Farquhar
authors.forename: Florian Felix
authors.initials: FF
authors.lastname: Pfaff
authors.forename: Uwe
authors.initials: U
authors.lastname: Kuhlmann
authors.forename: Peter
authors.initials: P
authors.lastname: Hildebrandt
authors.forename: Beatrice
authors.initials: B
authors.lastname: Braun
authors.forename: Claudio
authors.initials: C
authors.lastname: Greco
authors.forename: Kallol
authors.initials: K
authors.lastname: Ray
mesh_terms: D003300:Copper / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D058116:Lewis Acids / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012538:Scandium / Q000737:chemistry*; D014105:Tosyl Compounds / Q000737:chemistry*
chemical_list: D007097:Imines; D058116:Lewis Acids; D008698:Mesylates; D009942:Organometallic Compounds; D014105:Tosyl Compounds; C436603:scandium triflate; D003300:Copper; D012538:Scandium