Abstract
Chapter 1 Benzofuran derivatives are important molecules of heterocycles found in many natural and biologically active molecules and are often used as building blocks in organic materials.In chapter 1，a new strategy for the synthesis of highly substituted benzofurans from meta-substituted hydroxybenzenes and alkynes via a rhodium(III)-catalyzed activation of a sterically hindered C–H bond is demonstrated. A possible mechanism involving dual directing group assisted ortho C–H bond activation is proposed. Interestingly, the products we synthezied could support second C-H bond activation for further modification owing to the retention of O-methyloxime group attatched on them. Chapter 2 A novel copper-promoted multiple aza-[4 + 2] cycloaddition reaction of N-methyleneanilines generated in situ from benzylic azide and alkenes afforded quinolinium salts, biquinolinium salts, biquinolines or substituted quinolines depending on the substitution on the phenyl ring of benzylic azide.The reaction likely started by Lewis acidic CuII-assisted rearrangement of benzylic azide to N-methyleneaniline, followed by a [4 + 2] cycloaddition with alkene. Detailed mechanistic studies suggest that the biquinoline and biquinolinium salts are probably formed via radical processes. Besides the reaction of benzylic azides with alkenes, a one-pot multicomponent reaction of anilines, alkenes and formaldehyde was also investigated. Chapter 3 To continue our research result, we have successfully established an efficient copper-catalyzed aerobic oxidation of anilines, ketones and aldehydes to afford diverse functionalized N-aryl and -alkyl quinolinium salt in good to excellent yields.The reaction possibly proceeds via Lewis acid induced N-aryliminium ion and nucleophilic addition of enol formed of ketone. The cascade reaction is highly compatible with different π-components such as styrene, alkyne and activated alkenes as alternatives to ketones. Base on this study, we also improved the reaction in chapter 2 to an efficient copper-catalyzed aerobic oxidation reaction.