Preparation Of Novel Co-based Catalysts And Their Application In Condensation Reaction

The 2-arylbenzimidazoles,chalcones and their derivatives are important pharmacophores and molecular skeletons,showing a wide range of biological activities.Their synthesis methods have attracted much attention,and these compounds are usually synthesized by transition metal-catalyzed condensation reactions.It is of great significance to develop a green,economical and efficient transition metal supported catalyst for the synthesis of 2-arylbenzimidazoles and chalcones by condensation reaction.In this paper,a novel supported Co-based catalyst was designed and synthesized for the synthesis of 2-arylbenzimidazoles and chalcones by condensation reaction.Firstly,Co@MgF2-f-h catalyst with uniform microsphere morphology was synthesized by hydrothermal method assisted by hexamethylenetetramine(hmta)and ammonium fluoride(NH4F).A series of characterization(SEM,TEM,HADDF-STEM-EDS,XRD and H2-TPR)analyzed the main reasons for the good catalytic performance of Co@MgF2-f-h catalyst.The active component Co in Co@MgF2-f-h catalyst has a very small particle size and is highly dispersed,and there is a strong interaction between metal Co and MgF2 support.Next,the Co@MgF2-f-h catalyst was further used in the condensation cyclization reaction of o-nitroaniline and benzyl alcohol.By optimizing the reaction solvent,time,temperature and atmosphere,the optimal reaction conditions were determined as follows:toluene as the reaction solvent,110℃ for 24 h under N2 atmosphere.Under this catalytic system,22 2-arylbenzimidazole compounds were obtained,and the mechanism of condensation cyclization reaction was speculated.Subsequently,Co@MgF2-f-h catalyst was applied to the Claisen-Schmidt condensation reaction of benzaldehyde and acetophenone.By screening the reaction solvent,time and atmosphere,the optimal conditions for the condensation reaction were determined:toluene as the reaction solvent,110 ℃ for 12 h under N2 atmosphere.Under the reaction conditions,18 chalcone derivatives were synthesized,and the mechanism of Claisen-Schmidt condensation reaction was speculated.Finally,the Co@MgF2-f-h catalyst was tested for recyclability.The yield of the catalyst did not decrease after 6 cycles.The structure and morphology of the Co@MgF2-f-h catalyst after the reaction were tested.XRD,TEM and XPS proved that the active component Co in the catalyst did not leach after the reaction,and the particle size was very small and highly dispersed,indicating that the catalyst had good stability.