N ‐Hydroxyphthalimide (NHPI)‐Organocatalyzed Aerobic Oxidations: Advantages, Limits, and Industrial Perspectives

N-Hydroxyphthalimide (NHPI) is an efficient organocatalyst, capable of promoting free-radical processes via hydrogen atom transfer (HAT) reactions. The catalytic cycle promoted by the NHPI/phthalimide N-oxyl (PINO) system. PINO generation being a key step of the overall aerobic oxidation process, in most cases, the use of NHPI was proposed in combination with different cocatalysts or initiators. The chapter reports the catalytic mechanism that demonstrates the role of peracetic acid, generated in situ, in promoting the formation of PINO by undergoing molecule-induced homolysis with NHPI, while the acyl peroxyl radical resulted to be the effective epoxidizing agent. The process was successfully applied to the synthesis of propylene oxide in acetonitrile (MeCN). In this context, the NHPI-catalyzed oxidation approach has been widely investigated as an alternative route to the classical autoxidation process due to the evident opportunity to increase conversion and selectivity in the hydroperoxide, according to the catalytic cycle reported.