Co-Oxidation Processes Promoted by N-Hydroxyphthalimide/Aldehyde System.

Aldehyde autoxidation rates are very high even at room temperature and atmospheric pressure and this property has been often used to promote the so-called “co-oxidation” processes, in which a mixture of an aldehyde and another less reactive organic substrate is submitted to molecular oxygen. The present work is addressed to overcome the most recent developments in this field, covering the last decade. After a brief overview on significative co-oxidative processes mediated by aldehydes, we focus on the recent results reported by the authors for the selective epoxidation of olefins and the selective oxidation of alkylaromatic to the corresponding hydroperoxides promoted by the new N-hydroxyphthalimide (NHPI)/aldehyde catalytic system under mild aerobic oxidations. Enthalpic, polar, solvent and temperature effects are widely disclosed. Moreover, the free-radical reaction mechanism based on the in situ generation of phthalimido-N-oxyl (PINO) radical by means of the “molecule-induced homolysis” of NHPI is deeply investigated and supported by experimental evidences.