The Research Of Palladium-Catalyzed Intramolecular C-H Amination In Water And Visible-light-Promoted Synthesis Of Versatile Carbazoles From Aromatic Azides

Water has unique physical and chemical properties in nature; it could influence the selectivity and activity of chemical reactions. Over the past decades, the construction of carbon-carbon bonds, carbon-halogen bonds and carbon-oxygen bonds via metal-catalyzed have been successful developed in the aqueous systems; however, metal catalyzed C-H amination with water as a solvent still exist huge challenges.In the first part, we described realization of C-H amination through metallonitrene in the aqueous systems. With 2-azido-biphenyl as the substrate, Pd (OAc) 2 as catalyst and water as a solvent, the target product could be obtained by means of a microwave reaction apparatus. After optimizing the conditions, we found the reaction in water is more favorable than in the organic solvent. Then we screened the substrates containing different functional groups and found the -F,-Br, -Cl,-CO2Et,-CHO,-OMe groups which have an important role in organic synthesis were well tolerated. At the same time we could obtain some biologically active carbazole alkaloids in high yields. After a series of experimental performed, the mechanism of this reaction is proposed via a metallonitrene insertion of carbon-hydro gen bonds in the process. This method firstly achieved intramolecular C-H amination via metallonitrene in aqueous system.Carbazole skeleton is a great important framework. It’s not only widespread in the pharmaceutically active molecule, but also prevalent in excited by light and electron transfer organic materials. Great progress has been made for synthesis of carbazole; such as dehydrogenation coupling, C-H amination are accessions to carbazole. However, vast majority of these methods require the metal or excess oxidant involved, and the metal in the synthesis of drug molecules which also need to be removed in the final products, which improves the degree of difficulty and limited the scope of use.In the second part, we described a visible light promoted synthesized versatile carbazole from aromatic azides. With 2-azido-biphenyl as a substrate, water as a co-solvent, the desired product was able to be obtained under fluorescent lamp irradiation. After the optimized conditions, we found co-solvent of the water with acetone (1:1) came out best, and nitrogen is the solo byproduct of the reaction. Then we screened the substrates containing different functional groups and found the -halogen,-CO2Et, -CN,-CONHMe,-CHO,-OMe groups which have an important role in organic synthesis were well tolerated. Moreover substrates with a large steric hindrance and electron-rich characteristics could convert to the target product in high yields. In addition, the biologically active carbazole alkaloids were also achieved in high yields. These fully suggest it has wide and practical applications. After a series of experimental performed, the mechanism of this reaction is proposed via a nitrene insertion of carbon-hydrogen bonds during the process. This method first achieved versatile carbazoles via visible light promoted from aromatic azides.