Allylic Amination and Aziridination of Olefins by Aryl Azides Catalyzed by CoII(tpp): A Synthetic and Mechanistic Study

CoII(tpp) catalyzes the reaction of aromatic azides (ArN3) with nonactivated olefins to yield allylic amines or aziridines in moderate‐to‐good yields. The chemoselectivity of the catalytic reaction is particularly high. Depending on the substrate employed, allylic amines or aziridines can be obtaine...

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Bibliographic Details
Published in:European Journal of Inorganic Chemistry 2008, Vol.2008 (19), p.3009-3019
Main Authors: Caselli, Alessandro, Gallo, Emma, Fantauzzi, Simone, Morlacchi, Simona, Ragaini, Fabio, Cenini, Sergio
Format: Review
Language:English
Subjects:
Azides
C-H activation
Cobalt
Homogeneous catalysis
Porphyrinoids
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Summary:CoII(tpp) catalyzes the reaction of aromatic azides (ArN3) with nonactivated olefins to yield allylic amines or aziridines in moderate‐to‐good yields. The chemoselectivity of the catalytic reaction is particularly high. Depending on the substrate employed, allylic amines or aziridines can be obtained. The reaction mechanism was investigated, and the reaction proceeds through reversible coordination of the aryl azide to the CoII–porphyrin complex. The often postulated “nitrene” complex is not an intermediate in this reaction. The kinetics for the allylic amination is first order in azide, Co(tpp), and olefin. For the aziridination, the kinetics is again first order in azide and catalyst, but we observed a first‐order dependence of the rate on α‐methylstyrene only up to an olefin concentration of 6.9 M. An inhibiting role of the competitively formed 1‐(4‐nitrophenyl)‐5‐methyl‐5‐phenyl‐1,2,3‐triazoline was identified. The triazoline was shown to reversibly coordinate to Co(tpp), which blocks the free coordination site necessary for the catalytic reaction to proceed, and is it responsible for the catalyst deactivation in the aziridination reaction of α‐methylstyrene by 4‐nitrophenyl azide. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) CoII(tpp) catalyzes the reaction of aromatic azides with nonactivated olefins to yield allylic amines or aziridines in moderate‐to‐good yields. The reaction mechanism was investigated and found to proceed through reversible coordination of the aryl azide to the CoII–porphyrin complex. The often postulated “nitrene” complex is not an intermediate in this reaction.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.200800156