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. Nucleophilic superoxide: A copper(II)‐superoxide complex has been found to be a highly reactive nucleophile. The complex reacts readily with certain electrophiles and is capable of the nucleophilic deformylation of electron‐rich aldehydes (Baeyer–Villiger oxidation). These observations provide experimental support for the postulated nucleophilic reactivity of metal‐superoxide intermediates in the catalytic cycles of certain nonheme iron enzymes.