Oxidation processes catalyzed by non-heme iron complexes using H2O2 as the terminal oxidant, represent one of the most promising green and sustainable approach to selectively functionalize non-activated C-H bonds. These biomimetic models of nonheme iron enzymes are activated by H2O2 to give an iron(III) hydroperoxide which is the precursor of the iron-oxo complex active species.
In this research field, in the first part of our project the nonheme imine-based iron complex easily prepared by self-assembly of 2 picolylaldehyde, 2 picolylamine, and Fe(OTf)2, an efficient catalyst for aliphatic C H bond oxidations, will be tested in the oxidation of aromatic compounds with H2O2. This process represents an important biochemical transformation which is also relevant from an industrial viewpoint. By using a series of alkylaromatic substrates, the chemoselectivity of aromatic vs side-chain oxidation will be analyzed. Oxidation of halogenated aromatics is also planned as a possible green strategy for the degradation of polluting haloaromatic compounds.
The oxidation mechanism will also be investigated by means of theoretical and experimental studies including the analysis of the electronic effects of substituents on the aryl mojety, kinetic isotope effect determinations, use of radical scavengers, inter- and intramolecular substituent effects in rearrangement experiments.
The second part of the project will be dedicated to the analysis of the catalytic activity of a highly selective supramolecular catalyst obtained by assembling a bipyrrolidine iron complex with two crown ether recognition sites. This artificial nonheme iron enzyme will be tested as a catalyst in the oxidation with H2O2 of suitable substrates such as hydrocarbons functionalized with ammonium groups that could bound the crown ether with high affinity by means of hydrogen bonding. In fact, once complexed to the crown-ether recognition sites, these substrates could be selectively oxidized at a specific site.
