Catalytic Generation of Nitrosocarbonyls Under Mild Conditions: Advances, Challenges, and Opportunities.

Nitrosocarbonyl species (NOCs), also known as acylnitroso species, are highly reactive nitrogen-containing electrophiles. Since their first reports in the 1970s, they have shown significant synthetic potential for the preparation of aminated substrates. Their widespread adoption as versatile amination reagents began in the 2000s, driven by the development of new organometallic and organocatalytic systems. NOCs are typically generated in situ from stable precursors, such as hydroxamic acids and N-hydroxycarbamates, under oxidative conditions, in the presence of a scavenging substrate. This review highlights recent advances in NOC-based catalytic aminations over the past two decades. Specifically, their catalytic generation using oxygen, reactive oxygen species, and peroxides, followed by a subsequent capture through nitroso Diels-Alder, nitroso-ene, and nitroso-aldol reactions are comprehensively discussed. While most catalytic systems rely on Fe-, Co-, Ni-, Cu-, Mo-, Ru-, and Ir-based catalysts, emerging approaches include organocatalysis, photoredox catalysis, electrochemistry, and enzymatic systems. Sustainability and innovative process technologies are also discussed as future directions.