Cu-Catalyzed aromatic C–H imidation with N-fluorobenzenesulfonimide: mechanistic details and predictive models† †Electronic supplementary information (ESI) available: (1) CuIBr oxidation by NFSI; (2) details of the Br/F exchange process; (3) bimetallic oxidation of LCuIX (where X = F, Br, Cl, and I) by NFSI; (4) conformational analysis of the oxidation of D3-N-3F; (5) NBO analysis of the Cu2F2 dimer; (6) analysis of electronic states along the catalytic cycle; (7) energy scan for the deprotonation step; (8) isotope effect calculation; (9) calculation procedure to predict regioselectivity for C–H imidation; (10) kinetic profiles of product formation of pre-catalysts; (11) characterization data, 1H and 13C NMR spectra; (12) observation of the proposed intermediate D3-N-3F; (13) energies and Cartesian coordinates. See DOI: 10.1039/c6sc04145k Click here for additional data file

Dinuclear CuII–CuII intermediate is an active catalyst for an unusual stepwise two-electron oxidation by NFSI, a regioselectivity predictive tool and a new catalyst development.
The LCuBr-catalyzed C–H imidation of arenes by N-fluorobenzenesulfonimide (NFSI), previously reported by us, utilizes an inexpensive catalyst and is applicable to a broad scope of complex arenes. The computational and experimental study reported here shows that the mechanism of the reaction is comprised of two parts: (1) generation of the active dinuclear CuII–CuII catalyst; and (2) the catalytic cycle for the C–H bond imidation of arenes. Computations show that the LCuIBr complex used in experiments is not an active catalyst. Instead, upon reacting with NFSI it converts to an active dinuclear CuII–CuII catalyst that is detected using HRMS techniques. The catalytic cycle starting from the CuII–CuII dinuclear complex proceeds via (a) one-electron oxidation of the active catalyst by NFSI to generate an imidyl radical and dinuclear CuII–CuIII intermediate, (b) turnover-limiting single-electron-transfer (SET1) from the arene to the imidyl radical, (c) fast C–N bond formation with an imidyl anion and an aryl radical cation, (d) reduction of the CuII–CuIII dinuclear intermediate by the aryl radical to regenerate the active catalyst and produce an aryl-cation intermediate, and (e) deprotonation and rearomatization of the arene ring to form the imidated product. The calculated KIE for the turnover-limiting SET1 step reproduces its experimentally observed value. A simple predictive tool was developed and experimentally validated to determine the regiochemical outcome for a given substrate. We demonstrated that the pre-reaction LCuX complexes, where X = Cl, Br and I, show a similar reactivity pattern as these complexes convert to the same catalytically active dinuclear CuII–CuII species.