Photocatalytic C-H Bond Activation: Preparation Of Chroman Derivatives From 3-Aryl-1-propanols And Preparation Of Benzamide Derivatives From Benzylamines

As an atom-economical and step-economical methodology, direct functionalization of unreactive carbon-hydrogen bond to construct a new carbon-carbon bond or carbon-heteroatom bond is challenging and has attracted much attention in synthetic organic chemistry. Represented by transition metal activation of carbon hydrogen bond has been gradually mature, but, transition metal catalyzed reaction conditions are harsh generally and especially the use of heavy transition metals bring environmental burden. In recent years, photocatalytic carbon hydrogen bond activation has injected new vitality to carbon hydrogen bond activation area. Photocatalytic organic reaction is the reaction of the excited state,, comparing with the traditional organic reactions it can be done in room temperature and mild condition. Photochemistry reaction also has the characteristics of environmental friendly and good selectivity. Photocatalytic carbon hydrogen bond activation provides new ideas and methods for organic chemistry. In this dissertation, we use ultraviolet and visible light respectively activated the different carbon hydrogen bonds, and we got the target molecular with high efficiency and good selectivity. The outline and contents of this thesis are as follows:In Chapter I, a brief introduction of the basic theory and pathways of the photochemistry reaction is reviewed. In recent years under the photocatalytic carbon hydrogen bond activation of Csp3-H and Csp2-H research status are summarized, and focus on photocatalysis of benzylic carbon hydrogen bond activation and aromatic benzene carbon hydrogen activation and cross-coupling hydrogen evolution. Finally, this dissertation’s scientific significance of topic selection is elaborated.In Chapter II, we report a highly selective and good efficient photocatalytic intramolecular alkoxylation of 3-aryl-l-propanols with equivalent production of hydrogen gas under the ultraviolet light. This oxidant free photocatalytic system constructed by QuCN+C104 as a photosensitizer and cobalt complex as a catalyst in CH3CN. This dual catalyst system avoids the use of noble metals and toxic oxidants and reduces the steps of the reaction with atomic economy, and providing new idea and methods for preparation of chroman. The probable mechanism is also discussed.In Chapter III, we firstly report a photooxgenation Csp3-H reaction of N-protected benzylamines with O2 and acridinium catalyst under irradiation with visible light. This protocol selective oxidized various N-protected benzylamine to benzamides in mild condition with moderate to good yields. The reaction condition is mild and with no metal and toxic oxidants addition, Therefore the reaction system is satisfied with green chemistry concept and provide new ideas and methods for organic chemistry. A plausible mechanism was proposed on the basis of the mechanistic studies and previous literature reports.