Visible Light Induced C-C And C-O Bonds Formations And Mechanistic Studies

During recent years, visible light photoredox catalysis has been well developed as a novel and powerful tool to initiate various useful organic transformations. In this dissertation, we have described the recent advances in this field. Based on this visible light strategy, we presented our research work as follows:1. We develop a visible-light-induced oxidation/[3+2] cycloaddtion/oxidative aromatization sequence between dihydroisoquinoline esters and electron-deficient alkenes and alkynes. This method provides a rapid and efficient access to pyrrolo[2,1-a]isoquinolines. Based on control experiments and kinetic isotopic effect studies, we also propose a possible mechanism. Using this strategy as the key step for the synthesis of Lamellarin K is currently underway in our lab.2. We describe a visible-light-promoted aerobic oxidative hydroxylation of arylboronic acids. This protocol combines air with visible light in a single reaction and shows great substrate tolerance, which provides a variety of functionalized phenols and its analogues. O-18labeling experiments show that the hydroxyl oxygen of the product is from molecular oxygen. Computational investigations indicate the reaction pathway involves a boron-peroxo complex.3. A photocatalytic intermolecular [2+2] cycloaddition reaction of3-ylideneoxindoles has been developed through energy transfer pathway. This strategy affords oxindole derivatives which contain two spirocycles and four stereogenic centers, inculding two all-carbon quaternary centers. Based on the results of CV study,"on-off" switching of the light source and degass procedure, we exclude the electron transfer pathway.4. We also realize the condensation reaction of3-bromooxindoles, DMF and water. In this process, we successfully combine visible light and water into one reaction system. According to the fluorescence quenching experiments, we demonstrate the electron transfer from excited state photocatalyst to3-bromooxindole. Based on labeling experiments, we observe the formyloxy group is from DMF and water. Also,"on-off" switching of the light source study, MS studies and in situ IR experiments give some new insight into the mechanism of this transformation.