Azide-Radical-Enabled Hydrogen-Atom-Transfer And Its Applications In The Radical Addition Reactions Of Imines

As a relatively inexpensive and safe source of azide ions,TMSN₃ was often oxidized to azide radical in presence of oxidants and transition metal,and reacts with electron-rich unsaturated systems.In fact,the scientists studies of azide radical and olefin addition reactions have become relatively mature,however,there are relatively fewer studies on the azide radical participating hydrogen atom transfer processes,and the existing reaction systems employing azide radical used as a hydrogen atom transfer reagent（HAT）all require stoichiometric amount of oxidants and excess TMSN₃.The basic strategy studied in this dissertation is converting TMSN₃ to an azide radical to serve a hydrogen abstraction species under the induction of visible light,which abstracts the C_（sp3）–H bond with relatively low dissociation energy within the molecule,theαposition of the cyclic ethers and the allylic position of the silyl enol ethers could thus be activated.The main contents of the study are as follows:1)Under the induction of visible light,the azide radical catalyzes the radical addition recation of cyclic ethers to imines,and a series of cyclic ethers and imines addition products are obtained in excellent yields.We found that the radical addition products can also be hydrolyzed under the processes of Lewis acid to obtain indoles at the 2-position substituent in a medium or higher yield,and obtainβ-amino ether and threonine in a pretty yield（more than 80%）with high value product molecules.The reaction system does not require a"photosensitizer",and the substrates have good universality,it can afforded an excellent yield for different types of imines such as aromatic imines,ethyl acetate imines,trifluoroaldimines,and trifluoroketimines.Since the addition of azide radicals to alkenes known to be a reversible processes,therefore we get through brieflymonitor the isomerization processes of cis-alkenes,which indirectly prove that the reaction system may be carried out under the catalysis of azide radicals.In addition,we also try the classic azide radical system（i.e.,high iodine oxidation to produce azide radical）,and found that the reaction can also take place smoothly.The above shows that azide radical can promote the cleavage of C_（sp3）–H bonds in cyclic ether molecules and generate oxyalkyl radicals.2)Under the presence of light,2,3-butanedione as a photosensitizer,azide radical catalyzes the radical addition process of the allylic position of silyl enol ethers to the imines to obtain a series ofβ-functionalized products of aldehydes and ketones.After further hydrolysis of these products,high value-added derivatives such as pyrrole andγ-amino alcohol are obtained in a good yields.The reaction condition is mild,a range of substrates,and have good conversion and selectivity for cyclic ketones and open chain ketones.