Visible Light Catalyzed Trifunctionalization Of Unactivated Alkenes: A Modular Access To New Spiroaminals

Objective:Spirocyclic compounds have a wide range of applications in the fields of medicine,material,etc.Such as,they have activity of antimicrobial,antiviral and cytotoxicity,which attracted a large number of scientists around the world to devote themselves to researching its synthesis.Based on consideration for green and mild reaction,we aim to synthesize a series of spiroaminal compounds with novel structures through visible light-mediated cyclization of nitrogen free radical,providing some alternative Skeleton selection for development of new drug and material.Methods:The visible light catalyzed trifunctionalization of unactivated olefins with alkenyl azides was optimized to obtain a new skeleton of spiroketal amine.Through control experiments and mechanism verification experiments,a possible reaction process was proposed and the further derivatization and transformation of the template product were also implemented to explore its application value.Results:Under the protection of argon,fac-Ir（ppy）₃（2 mol%）as a photosensitizer,K₂CO₃（1.5 eq）as a base,anhydrous DMSO（2.0 m L）as a solvent,irradiated with 30 W blue light,and reacted at room temperature for 6 h The reaction could provide a novel spiroketal amine compound with a yield of35%～80%,including 34 spirobispyrrolines and 18 spiropyrroline lactams.Moreover,the obtained product could be modified to derived compounds via hydrolysis,addition,and substitution reactions,such as aromatized pyrroline and chlorine-substituted spiroaminal,etc.Finally,through mechanism study,possible reaction process was proposed,namely:nitrogen radical cyclization,1,5-hydrogen atom transfer,nitrogen radical translocation and recyclization process.Conclusion:The synthesis of spiroaminal compounds through the visible light catalyzed trifunctionalization of unactivated olefins with alkenyl azides has the advantage of mild condition and broad scope of substrates.In addition,some simple means could be used to achieve structural diversification of the product.Finally,through corresponding mechanism experiments,possible reaction mechanism has been proposed.