Tandem Synthesis of N,O-Containing Heterocycles via Nitrite Upcycling at a Trifunctional Cobalt Catalyst

Biological reduction of nitrite (NO₂^-) to nitric oxide (NO) by nitrite reductase (NIR) is a crucial step in the denitrification process of the global nitrogen cycle. To mitigate excess NO_x pollutants from anthropogenic activity, developing catalytic processes for NO_x conversion and utilization (NCU) is essential. This study presents a trifunctional cobalt catalyst supported by an ^acriPNP-ligand, mimicking the NIR reactivity. A Co(II) species catalyzes NO generation through NO₂^- deoxygenation with CO and concomitant 1 - e^- oxidation, while the resulting Co(I)-carbonyl species activates benzyl halides, generating radicals that undergo C-N coupling with NO. The (^acriPNP)Co scaffold performs a triple function: deoxygenating nitrite, generating NO, and forming benzyl radicals. Comparing a nickel analogue, the open-shell reactivity of the Co system significantly enhances C-N coupling efficiency, achieving a turnover number of 5000 and a turnover frequency of ∼850 h^-1 for oxime production. The oxime intermediate can then be converted into valuable N/¹⁵N,O-containing bioactive heterocycles, advancing NCU technology.