Dioxygen-Triggered/Participated Radical Oxidative Coupling Reactions And Mechanistic Investigation

As a classic arsenal in synthetic chemistry, radical chemistry has led the revolution of organic synthesis since1930s. In the new century, radical chemistry has been creating a renaissance with the upsurge of interest in transition metal catalysis and photocatalysis. Up to now, seeking the more green radical transformations and controlling the reaction selectivity more effectively still remain as the major challenges in radical chemistry. Moreover, the lack of solid physical organic understanding of the mechanism has also largely hold back the pace of the radical chemistry.In this thesis, a brief introduction of the history as well as the state-of-the-art research in radical chemistry were first reviewed. Then the dioxygen-involved radical reactions were surveyed in details. Directed by the idea of simple chemistry and the law in radical chemistry, the research work of this thesis focused on dioxygen-trrigered/participated radical oxidative coupling reactions. At the same time, in-depth kinetic and mechanistic research will be performed to gain insightful discipline of the radical reactions. Details are as followings:1. Based on the autoxidation of sulfinic acids, an unprecedented dioxygen-triggered oxidative radical process using dioxygen as the solely terminal oxidant was successfully developed, in which organic base was utilized to successfully surpress ATRA (atom transfer radical addition) process and to reduce the activity of sulfinic acids, thus realizing aerobic oxysulfonylation of alkenes, alkynes, allenes with high selectivity and the formation of new C-O and C-S bond in one-pot. Importantly, the novel methods proceeded without any additional initiators and realized dioxygen fixation by sulfinic acids, which made this transformation sustainable and environmentally friendly.2. According to the p-pπ orbital conjugate effect between heteroatom and radical adjacent chain, a-heteroatom substituted styrenes were designed to control the chemical selectivity in radical oxygenation reactions, leading radical thiolation/oxygenation of activated alkenes proceeded spontaneously at room temperature with no need for any additives. Notably, sustainable water could be further employed as the reaction medium and other radical Cvinyi-heteroatom bond oxygenation processes including dioxygenation, oxysulfonylation of activated alkenes were also performed well.3. Operando IR experiments disclosed an unprecedented interaction between CF3SO2· and O2, which could further reinitiate radical chain process. Based on this information, O2and catalytic amount of K2S2O8work in concert to activate CF3SO2Na was proposed and a convenient radical oxytrifluoromethylation of activated alkenes was achieved without assistance of additional transition-metal catalysts or stoichiometric organic oxidants. A series of a-trifluoromethyl-substituted ketones could be synthesized from CF3SO2Na and O2under simple conditions.4. Based on the particular behavior of hydroxamic acid and abundant metal catalysts, radical dioxygenation of simple alkenes was successfully developed, in which various ketones and teritiary alcohols could be synthesized with high selectivity via tuning the catalyst precusors and substrates. Futhermore, copper-catalyzed radical dioxygenation and oxysulfonylation of electron-withdrawing alkenes with O2through aerobic decarboxylative process can also be applicable to this simply catalytic system. Not only that, radical oxidative Csp3-O coupling reaction has been realized under similar conditions as well.