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Lewis Acid Trapping of an Elusive Copper-Tosylnitrene Intermediate Using Scandium Triflate
Citation key Kundu2012
Author Kundu, Subrata and Miceli, Enrico and Farquhar, Erik and Pfaff, Florian Felix and Kuhlmann, Uwe and Hildebrandt, Peter and Braun, Beatrice and Greco, Claudio and Ray, Kallol
Pages 14710–14713
Year 2012
DOI 10.1021/ja306674h
Journal Journal of the American Chemical Society
Volume 134
Number 36
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/(CuNR)-N-II-R-center dot 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 degrees C enabled its characterization with optical, resonance Raman, NMR, and X-ray absorption near-edge spectroscopies, which helped to establish its electronic structure as (CuNTs)-N-II-Ts-center dot (Ts = tosyl group) and not (CuNTs)-N-III. 3-Sc can initiate tosylamination of cyclohexane, thereby suggesting (CuNTs)-N-II-Ts-center dot cores as viable reactants in oxidation catalysis.
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