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.