Nucleophilic Reactivity of a Copper(II)-Superoxide Complex

Metal‐bound superoxide intermediates are often implicated as electrophilic oxidants in dioxygen‐activating metalloenzymes. In the nonheme iron α‐ketoglutarate dependent oxygenases and pterin‐dependent hydroxylases, however, FeIII–superoxide intermediates are postulated to react by nucleophilic attack on electrophilic carbon atoms. By reacting a CuII–superoxide complex (1) with acyl chloride substrates, we have found that a metal–superoxide complex can be a very reactive nucleophile. Furthermore, 1 was found to be an efficient nucleophilic deformylating reagent, capable of Baeyer–Villiger oxidation of a number of aldehyde substrates. The observed nucleophilic chemistry represents a new domain for metal–superoxide reactivity. Our observations provide support for the postulated role of metal–superoxide intermediates in nonheme iron α‐ketoglutarate dependent and pterin‐dependent enzymes. Nucleophiles Superoxid: Ein Kupfer(II)‐Superoxid‐Komplex ist bei niedrigen Temperaturen (−80 °C) hochreaktiv und reagiert als Nukleophil mit diversen Elektrophilen. Zum Beispiel kann es elektronenreiche Aldehyde nukleophil deformylieren (Baeyer‐Villiger‐Oxidation). Diese Ergebnisse bestätigen die postulierte nukleophile Reaktivität von Metall‐Superoxid‐Zwischenstufen in Katalysezyklen bestimmter Nonhäm‐Eisen‐Enzyme.