Radical-Type Aziridination with [Co^III(TAML^red)]– in Water; Understanding and Preventing Epoxidation via Nitrene Hydrolysis

13 April 2022, Version 1
This content is an early or alternative research output and has not been peer-reviewed by Cambridge University Press at the time of posting.


Base-metal catalyzed nitrene transfer reactions in water are challenging, but have the potential to broaden the range of applications. Typically, these reactions suffer from the formation of oxygen containing side-products, of which the origin is not fully understood. Therefore, we set out to investigate aqueous styrene aziridination, using a water-soluble [Co^III(TAML^red)]– catalyst known to be active in radical-type nitrene transfer in organic solvents. The cobalt-catalyzed aziridination of styrene in water (pH = 7) yielded styrene oxide as the major product, next to minor amounts of aziridine. Based on 18O-labeling studies and catalysis experiments, we show that styrene oxide formation proceeds via hydrolysis of the nitrene-radical complex [Co^III(TAMLsq)(N•Ts)]–. Computational studies support that this process is facile and yields an oxyl-radical complex [Co^III(TAML^sq)(O•)]–, which is active in oxygen atom transfer to styrene. Based on these mechanistic insights, the pH was adjusted to afford selective aziridination in water.


nitrene radical
oxyl radical

Supplementary materials

Supporting Information
Supporting Information belonging to the paper


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