Application Of Visible-Light-Induced Wolff Rearrangement In Palladium-Catalyzed Asymmetric Dipolar Cycloadditions

Ketenes are a class of versitatle synthons in organic chemistry,which are widely used in the organocatalytic and Lewis acid catalyzed cycloaddition reactions leading to a wide range of significant hetereocycles.However,the ketene cycloaddition through transition metal catalysis are still under-developed due to the unfavored decarbonylation,polymerization and other competitive processes in the presence of transition metal catalyts.Therefore,the development of such cycloadditions is of great significance from the perspective of enriching the ketene cycloaddition chemistry and contructing new cyclic skeletons by rationally designing the new reactions and exploiting the appropriate catalytic systems,especially the chiral ones.For this purpose,in this PhD thesis we developed palladium-catalyzed asymmetric[5+2],[4+2]and[3+2]cycloaddition reactions with ketones by introducing visible-light-induced Wolff rearrangements.By doing so,a wide range of chiral 5-7 oxyheterocyclic motifs were constructed in high reaction efficiency and selectivity.To be more specific:Firstly,we accomplished a palladium-catalyzed Wolff rearrangement/asymmetric[5+2]cycloaddition sequential reaction of ?-diazo ketones and indane-1,3-dione-2-spirovinylcyclopropanes under visible light irradiation.By using chiral P,S ligand developed by our group,a series of chiral seven-membered lactones were produced with high efficiency and enantioselectivity(52-92%yields,87:13-99:1 er,up to 12.5:1 dr).Moreover,DFT theory calculation and ESI-MS experiments were performed to illustrate the reaction mechanism and explain the peri-and chemo-selectivity.Secondly,we further developed a palladium-catalyzed Wolff rearrangement/asymmetric[4+2]cycloaddition sequential reaction of ?-diazo ketones and 2-alkylidenetrimethylene carbonates under visible light irradiation.By using chiral phosphoene ligand developed by Carreira,a variety of chiral six-membered lactones bearing chiral all-carbon stereocenters were obtained with high efficiency and enantioselectivity(53-95%yields,71:29-98:2 er,up to>95:5 Z/E).Meanwhile,in order to demonstrate the synthetic practicability,the bifunctional reaction and reductive hydrogenation of the product were realized,and the enantioselectivity of the product was almost not affected.Finally,we explored a palladium-catalyzed Wolff rearrangement/asymmetric[3+2]cycloaddition sequential reaction of ?-diazo ketones with 2-cyanocarboxylate substituted vinylcyclopropanes under visible light irradiation.By using chiral biphosphine ligand developed by Trost,a range of chiral highly substituted tetrahydrofurans were successfully synthesized with high efficiency and enantioselectivity(52-99%yields,80-98%ee,up to>95:5 dr).All the products were confirmed by NMR and MS characterization,and the representative products were further confirmed through X-ray single crystal analysis.