Asymmetric[8+2]Dipolar Cycloadditions Enabled By Palladium Catalysis And Visible Light Excitation

Medium-sized ring compounds,especially ten-membered ring,are an important class of cyclic skeletons,which are widely found in natural products and some biologically active molecules.Traditional higher-order[8+2]cycloaddition reactions usually can be used to construct a[5,3,0]structure containing a ten-membered ring skeleton.On the other hand,asymmetric high-order dipolar cycloaddition reactions based on palladium-catalyzed allylation are considered to be a novel and effective method for constructing medium-sized ring compounds.However,higher-order[8+2]dipolar cycloaddition has never been reported.In this thesis,we studied the palladium-catalyzed/photo-induced asymmetric[8+2]cycloaddition by using the P,S ligands developed by our group.In the process of ring opening,by changing the protecting group of vinyl oxazinanones,the 1,8 dipoles could be afforded without releasing CO2 under the palladium catalysis.Considering the efficiency and enantioselectivity of the reaction,P,S ligands were found to be the optimal ligands for this reaction after screening different ligands.After investigation of the substrate scope,we found that a variety of ten-membered ring compounds containing a quaternary carbon could be given smoothly in 70%-97%yield and up to 97:3 er value.The structures of all new compounds were confirmed by 1H NMR,13C NMR,HPLC,optical rotation and mass spectrometry.In addition,according to previous literature reports and DFT calculations,we proposed a possible mechanism for this reaction.