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A wide variety of systems are being researched with the goal of functionalizing distant unfunctionalized (alkane) carbons using updated versions of the Hoffmann-Löffler-Freytag (HLF) reaction. [1] The induced cleavage of sulfonamides with iodine and a co-oxidant is one of the more popular methods within the HLF reaction procedures. In such procedures, an N- radical is generated via homolytic cleavage of the N–I bond, when iodosulfonamide, an intermediate product, is photochemically activated. [2] Considering that N radicals are unstable intermediates, the stability of such radicals, which is described in the work done by Šakić and Zipse, [3] determines their concentration and thus the possibility of detection using the electron paramagnetic resonance (EPR) devices. A series of differentially N- substituted amines was prepared in good to excellent yields in order to activate the N–H bond thereby producing the coveted N-radicals which take part in rearrangement as described in the HLF reaction mechanism. The identity of these compounds was confirmed by 1H, 13C NMR and IR measurements. These N-centered radicals have already been detected via EPR measurements and described by the Muñiz group, [4] ; however, Khort [5] has done extensive theoretical calculations and therefore has raised some serious doubts regarding this work. Herein, we provide results collected from EPR experiments regarding detection of the N-centered radicals utilizing spin traps, along with theoretical calculations to serve as support and elucidation of the experiments. References [1.] L.R. Reddy, B.V.S. Reddy, E.J. Corey, Organic Letters 8 (2006) 2819-2821. [2.] T. Duhamel, C.J. Stein, C. Martínez, M. Reiher, K. Muñiz, ACS Catalysis 8 (2018) 3918-3925. [3.] D. Šakić, H. Zipse, Advanced Synthesis and Catalysis 358 (2016) 3983-3991. [4.] A.E. Bosnidou, T. Duhamel, K. Muñiz, European Journal of Organic Chemistry 2020 (2020) 6361- 6365. [5.] H. Korth, European Journal of Organic Chemistry 2020 (2020) 6366-6367. |
