Studies On Single Electron Transfer Oxidative C-C/N Bond Cleavage Reaction

With the development of society and technology, the level of industry has reached a new high, in the meantime, it also gives rise to a series of energy crises and environmental pollution. Thus, looking for new green and nonpolluting energy, as well as developing new types of chemical reaction under mild reaction conditions, is a long-term goal for chemists to pursuit.This Thesis focuses on visible light and ammonium persulfate induced single electron transfer reaction to realize oxidative cleavage reactions of C-C and C-N bonds.As an emerging research field of organic chemistry, the study of visible light induced single electron transfer reactions has been receiving more and more attention over the past few years. For the goal of green catalytic chemistry, visible light is undoubtedly the most ideal reagent, due to its nonpolluting property, renewability and easy accessibility.Applying visible light induced strategy, an oxidative C-C bond cleavage of aldehydes at ambient temperature and under air atmosphere was studied. The results showed that this reaction could be realized under mild conditions with good yields(70-96%), being compatible with a broad range of aryl and cyclic/acyclic alkyl alhydes. Moreover, we further demonstrated its application in a tandem Michael/oxidative C-C bond cleavage reaction, providing a novel synthetic method for cyclopentanone compounds. The mechanism of this visible light induced oxidative C-C bond cleavage of aldehydes was also investigated. A control experiment in which 2,2,6,6-tetramethyl-1-piperidinyloxy(TEMPO) was added to capture radicals was conducted to add more credence to the existence of imine cation radical intermediate.Aziridines, a class of three-membered saturated heterocycles, are versatile building blocks for the synthesis of many nitrogen-containing molecules. Applying visible light induced strategy, a regioselective ring-opening nucleophilic addition of the N-tosylaziridines with three kinds of nucleophils(alcohols, Li Br and Na N3) was studied. Moreover, enantioselective sythesis of 1,2-amino esters was realized utilizing optically pure aziridines. The synthetic utility of the ring-opening products was exemplified by further transformations of the azide functionality. Finally, a possible reaction mechanism was proposed and a control experiment was carried out with the addition of methyl vinyl ketone(MVK) as a radical scavenger, providing a clear understanding of the reaction mechanism.Showing remarkable biological and pharmacological activities, morpholine moieties are considered as crucial cores in structures of numerous natural and synthetic products. In particular, a number of 2-substituted and 2,3-disubstituted morpholines have been chosen as new drug candidates, part of which have already been clinically available drugs. However, the existing synthetic methods of morpholines rely on metal catalysis, and there is still a deficiency of synthetic approaches to 2-substituted and 2,3-disubstituted morpholines. Persulfate salts, as a kind of single electron transfer oxidative reagent, are often used to induce oxidative reactions in organic synthesis. Persulfate salts induced metal-free reactions are in accordance with green chemistry, due to their non-toxic and environmentally friendly properties. Applying ammonium persulfate induced strategy, a metal-free reaction of aziridines with halogenated alcohols to synthesize 2-substituted and 2,3- disubstituted morpholines was studied. Moreover, the enantioselective synthesis of morpholines was realized ultilizing chiral aziridines with good enantioselectivity. In accordance with the green chemical process, this protocol could be performed at room temperature, through simple one pot strategy, and without metal catalyst.