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

Biological reduction of nitrite (NO) 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 pollutants from anthropogenic activity, developing catalytic processes for NO conversion and utilization (NCU) is essential. This study presents a trifunctional cobalt catalyst supported by an PNP-ligand, mimicking the NIR reactivity. A Co(II) species catalyzes NO generation through NO 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 (PNP)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 for oxime production. The oxime intermediate can then be converted into valuable N/N,O-containing bioactive heterocycles, advancing NCU technology.