Application of oxygen-centered radical and radical-like species for the selective oxidation of organic compounds

The selective functionalization of aliphatic C-H bonds is a research topic of growing interest in organic chemistry. The benefit of this approach is that functional groups can be introduced directly onto poorly reactive groups with no intermediate steps needed, allowing shorter and more efficient synthetic processes. Another important application is late-stage functionalisation, where structural changes can be made to complex molecules without the design of a new synthetic procedure from the beginning. Among the available strategies for C–H bond functionalization, increasing attention has been devoted to hydrogen atom transfer (HAT) based procedures promoted by radical or radical-like reagents, that offer the opportunity to introduce a large variety of atoms and groups in place of hydrogen under mild conditions. This thesis addresses the issue of selectivity, in its various aspects, in reactions promoted by different oxygen-centered radical or radical-like reagents. Regarding site-selectivity a potential approach for promoting functionalization of poorly reactive C–H bonds using a supramolecular strategy is proposed. In particular, two catalysts featuring a supramolecular site, a crown ether function, will be introduced. The first is an organocatalyst containing N-hydroxyphthalimide as the catalytic core, while the second is a photoorganocatalyst based on benzophenone. Another aspect of selectivity explored in this work is chemoselectivity. A study was conducted on oxidative processes using [(N4Py)FeIV(O)]²⁺ in combination with the mediator NHPI. This investigation focuses on the effect of NHPI in the competitive oxidation of alkyl aromatic compounds, alcohols, and aryl sulfides, promoted by [(N4Py)FeIV(O)]²⁺, using a detailed kinetic and product analyses. In addition, the oxidation mechanism of sulfides and sulfoxides promoted by TBADT was investigated. This research allows for the evaluation of whether the process follows a HAT or ET-PT pathway, depending on the substrate. Moreover, the distinct oxidation products are generated according to the specific mechanism involved. The oxidation of a series of alkyl sulfides promoted by the phthalimide N-oxyl radical (PINO) was also studied by kinetic and product analysis in order to gain a detailed understanding of the S-oxidation process promoted by PINO. Finally, a system capable of promoting enantioselective photoinduced HAT reactions was developed. In this study, a new chiral phosphoric acid was synthesized that will be anchored to a photocatalyst designed to enable enantioselective C–H bond functionalization