Metal-Free Synthesis Of N-Vinylated Azoles And Their Electronic Structure And Fluorescence Properties

N-vinylated azoles are important precursors for synthesis of many materials,drugs and pesticides because of their high biological activity and chemical stability.N-vinylated azoles could be synthesized by metal catalyst and metal-free catalyst.Metal catalyst takes advantage of only requiring a small amount catalyst and short reaction time to synthesize N-vinylated azoles,but the deprotonation of azoles is difficult to be controlled.More,the high-energy azole rings are potentially dangerous in the presence of metal catalyst.In recent years,synthesis of N-vinylated azoles under metal-free conditions has attracted much more attention in the field of organic synthesis,due to the advantages of easy experiment operation,mild reaction conditions,high yield and environmental friendliness.According to this background,azoles are used as substrate to N-vinylated compounds under mild conditions in this study.Furthermore,the reaction system was also calculated and analyzed based on density functional theory(DFT).Besides,(2E)-2-(2-propenoic acid methyl ester)-5-phenyl-tetrazole could be used as a metal fluorescence probe.The detailed works are summarized as follows:Firstly,the 5-phenyl-1H-tetrazole was explored as a substrate for N-vinylation.By exploring the optimal conditions,the experimental result shows that the conditions of 5 equivalents of triethylamine,DMSO as solvent,near room temperature and 2 hours for the reaction that gives N-vinylated tetrazoles with excellent stereoselectivity.According to the above,other azoles were synthesized such as N-vinylated triazoles and N-vinylated imidazolines.Secondly,based on the DFT and solvent effect,we explored the rational reaction sites of 5-phenyl-IH-tetrazole and calculated its infrared spectroscopy,thermodynamic function,bond length and other properties.The calculation results shows that DMSO can promote the C-N coupling of tetrazoles,and the order of reactivity is N(2)>N(4)>N(3).The product's pseudo-bond length could excellently represent the actual bond length,and the outstanding infrared vibration frequency was reflected in methyl C-H stretching,alkenyl C-H swinging,C=C stretching,benzene ring deformation and carbonyl stretching.Finally,the fluorescence of(2E)-2-(2-propenoic acid methyl ester)-5-phenyl-tetrazole was explored.The experimental results show that the maximum excitation wavelength is 310 nm and the maximum emission spectrum is 375 nm,which can be effectively used in the detection of Fe3+in methanol solution.