Synthesis Of Tetrahydroquinoline By Asymmetric Reduction Of Aminochalcone Based On Photocatalysis

Tetrahydroquinoline are an important part of organic compounds.We can easily trace traces of tetrahydroquinoline compounds in natural products,in pharmaceuticals,and in small organic catalysts.In this paper,we introduced the application of tetrahydroquinoline compounds in chemistry and pharmacy,and we also summarized the synthesis methods of tetrahydroquinoline compounds.On the synthesis of tetrahydroquinoline,we focused on the synthesis of N-C2 bond to synthesize tetrahydroquinoline,the formation of C2-C3 bond to synthesize tetrahydroquinoline,Povarov reaction to synthesize tetrahydroquinoline,and direct reduction of quinoline synthesis,this four synthetic methods of hydrogen quinoline.The asymmetric reduction of carbon-carbon double bonds and carbon-nitrogen double bonds is still a hot topic in organic synthesis today.The core of the asymmetric reduction reaction is the higher stereoselective reduction of olefins or imines to alkanes or amines by the action of a reducing agent and a chiral catalyst.In this paper,a brief summary of the asymmetric reduction of olefins,imines and aromatic rings in the Hantzsch ester and Br?nsted acid systems is given.At the same time,the visible light photocatalytic reaction is introduced.Here we mainly introduced the influence of visible light on the chalcone substrate.Finally,the current status of the natural synthesis of martinellic acid is summarized.Based on the reports in the literature,we have further studied the asymmetric reduction of olefinimine in Hantzsch ester and Br?nsted acid systems.We used 2-aminochalcone as a substrate to form 2-phenylquinoline under the catalysis of visible light,and then asymmetrically reduce to 2-phenyltetrahydroquinoline by Hantzsch ester and Br?nsted acid.The one-pot synthesis of tetrahydroquinoline with 2-aminochalcone as a raw material provides a simple and efficient method for the synthesis of natural products of tetrahydroquinoline.In this paper,by screening and optimizing the conditions,the template reaction can reach 70% yield and 99% ee value.Through the investigation of the universality of the substrate,it is shown that the reaction is applicable not only to the arylaminochalcone but also to the disubstituted alkyl chalcone,and it is possible to construct two consecutive chiral centers in one step.Based on the excellent universality of the reaction,we obtained the important tetrahydroquinoline intermediate with the necessary chalcone as the substrate by using the method with a 91% ee value of 1.3:1 dr.Then,the skeleton of the natural product martinellic acid was synthesized by a series of reactions such as osmium tetroxide oxidation,sodium borohydride reduction,Mitsunobu reaction,and free radical ring closure.