Stereoselective Reduction Of Azaaryl Ketone Catalyzed By Photo-redoxand Chiralprotonic Acid

The photochemical reactions have been developed rapidly in recent years due to the advantages of sustainability,environmental friendliness,and lower energy consumption.With the deep understanding of renewable energy,chemists have achieved remarkable results with visible-light as the driving force in various transformations.Asymmetric catalysis is currently an efficient way to prepare optically pure molecules,but traditional asymmetric catalysis methods are difficult to achieve stable conversion of the ground state.so it is urgent to develop a complementary methodology for traditional asymmetric catalysis.In this context,visible light-induced asymmetric photochemical synthesis came into being,which not only conforms to the concept of "green chemistry",but also can develop chemical conversion reactions that have not been achieved by classical ground state catalytic means.Asymmetric photochemical synthesis includes a variety of forms,and our research group is mainly devoted to the development of a cooperative catalytic strategy combining photo-redox catalysis and organic catalysis.With this strategy,we have realized the construction of a variety of important biologically active molecules.The research literature found that ?-hydroxyazaaromatics and their derivatives are many natural products and the basic skeleton of pharmacologically active molecules widely exists in nature.The most direct and effective way to obtain such compounds is the selective reduction of azaaryl-base ketones.However,its asymmetric reduction has several challenges: First,both the azaaromatic hydrocarbon part and the ketone part are electron-withdrawing groups,and the two groups may activate each other in the reaction,resulting in poor reaction selectivity;Second,since the nitrogen-containing heterocycles may poisons metals and Lewis acid catalysts during the reaction,their catalysts are often difficult to recycle;Third,the choice of reducing reagents.In addition to the highly dangerous gas such as H2,finding a stable and safe reducing agent is also a big problem.Based on this consideration,this subject uses a photocatalytic redox and asymmetric catalysis strategy.that is,With the aid of the dual-catalyst system of organic photosensitizer DPZ and chiral protonic acid independently developed by the laboratory,the enantioselective reduction of azaaryl ketone was carried out under visible light induction.The conversion process includes a series of two-step one-electron reduction and enantioselective protonation,and finally the synthesis of chiral secondary alcohols substituted with azaarene-substituted is achieved.This strategy takes advantage of the neutrality of photo-oxidation-reduction to overcome the difficulty of chiral catalyst recycling;at the same time,it has developed a high stereoselective reduction of unmodified azaaryl-base ketones;in addition,various azaaromatic rings including quinoline,Phoridine,benzothiazole,benzimidazole,etc.can achieve this type of conversion well.