Photocatalytic Construction Of C-N Bonds Based On Hydrazines

Carbon-nitrogen bonds are widely found in pharmaceuticals,pesticides,natural products and material molecules.The construction of C-N bonds is often a key step in molecular synthesis.Therefore,the efficient construction of C-N bonds under mild conditions has been one of the most popular studies.In this paper,we carried out visible-light-induced multi-component reactions to construct different types of C-N bonds without the addition of additional ligands,oxidants and reducing agents.The substrate scope of the two photocatalytic synthesis methods and their reaction mechanisms were also fully investigated,and the main research works are as follows.(1)Hydrazonamides are fundamental building blocks in many pharmaceuticals and agricultural chemicals.Although previous methods have been developed through multi-step reactions under harsh conditions,achieving high efficient synthetic strategy remains challenging.Considering the structural characteristic of hydrazonamides,a sequential multi-component reaction ofb-ketonitriles with N,N-disubstituted hydrazines is designed and accomplished through photocatalyzed decyanation and intermeolecular amination process.The reaction mechanism was studied by mechanism experiments.This work reported here represents the first example of the use of the N,N-disubstituted hydrazines as two different“amine”sources,and is characterized by isotope labeling experiments.The C-CN/N-N bonds are cleaved and new C-N/C=N bonds are constructed in one-pot reaction.This protocol can be carried out without the addition of any external metals,ligands,bases,oxidants and reductants,and possesses the advantages of operational-simple,mild reaction conditions,and good functional group tolerance.Furthermore,this approach enables late-stage modifications of structural complex bioactive molecules,natural products and drugs,thus showing potential applications in the field of organo-pharmaceutical chemistry.(2)Based on the above work,we developed the novel strategy for the syntheisis of?-trifluoromethylamine compounds in one pot from phenylhydrazines,Togni's reagent and styrenes.This method uses phenylhydrazines as the nitrogen sources and the inexpensive organic dye Rose Bengal as the photocatalysts.Under the irradiation of light,the N-N bonds of phenylhydrazines are cleaved to construct new C-N bonds,and the generated·CF₃ radical is added into the olefins to form C-CF₃ bonds.The method has the advantages of available starting materials,mild reaction conditions and simple operation.In addition,iodofluoroalkanes as the fluorine sources can also complete the conversion well using Ru(bpy)₃Cl₂ as the photocatalysts.