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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.

SUBMITTER: Kundu S 

PROVIDER: S-EPMC3743661 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Lewis acid trapping of an elusive copper-tosylnitrene intermediate using scandium triflate.

Kundu Subrata S   Miceli Enrico E   Farquhar Erik E   Pfaff Florian Felix FF   Kuhlmann Uwe U   Hildebrandt Peter P   Braun Beatrice B   Greco Claudio C   Ray Kallol K  

Journal of the American Chemical Society 20120831 36


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 accessibilit  ...[more]

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