Visible-Light-Induced Heterocycle Tethered C(sp~3)-H Bond Selective Functionalization

Visible light induced photoreaction is one of the popular research fields developed in recent years to convert light energy into chemical energy,and visible light induced selective functionalization of C-H bonds avoids the pre-activation of substrates and directly functionalizes compounds,reducing waste emissions and improving atomic economy.Due to the use of visible light as a clean energy source,it is more consistent with the concept of green chemistry and sustainable development than the traditional transition metal catalyzed C-H bond functionalization.Based on the latest research progress of visible-light-induced C-H bond functionalization,this thesis focused on visible light induced oxidative hydroxylation of 3-ester-2-oxindoles and co-catalysis system by copper catalysis and photocatalysis for the selective functionalization of ethers.The specific research contents are as follows:(1)A series of 3-ester-2-oxindoles derivatives were constructed from commercially available substrates.The C(sp~3)-H of 3-position in 3-ester-2-oxindoles were successfully activated under the optimized photocatalytic conditions with 3-hydroxyl-3-ester-2-oxindoles derivatives delivered in up to 89%yield.In addition,under the standard conditions 3-phenyl-2-oxindoles was also compatible.In the absence of base and stoichiometric oxidants,the reaction could also be successfully extended to the oxidative hydroxylation of 3-ester-2-oxindoles derivatives with allyl and H protecting groups on the nitrogen.Finally,a possible mechanism was proposed based on previous work related to the synthesis of indole derivatives induced by visible light.(2)The research related to the combination of visible light induced photoreaction and transition metal catalysis has gradually received widespread attention from researchers both domestic and abroad.In this context,a C(sp~3)-H functionalization of tetrahydrofuran with diazo ester derivatives as substrates was successfully achieved by a combination of photocatalysis and copper catalysis.The strategy had mild reaction conditions and moderate yields in character,and both photocatalysts and copper catalysts were indispensable parameters.Moreover,most diazo malonate were suitable to apply to the optimized conditions.Besides,1,4-dioxane could also be used to obtain functionalized target compounds with 40%yields.