Synthesis Of Acetals By Heterogeneous Photocatalytic Methods

Acetal is an important organic compound,which can be used as flavoring additives and aroma enhancers in cosmetic and food products or as anti-freezing additives in biodiesel fuels.Acetal reactions is one of the main methods to protect carbonyl groups,so the synthesis of acetals is particularly important.The most common method is using acid catalysis.Recently,electrocatalytic and photocatalytic methods for synthesis of acetals have been developed.There are few studies on heterogeneous photocatalytic methods.The heterogeneous photocatalysts are convenient to separate from the reaction system and easy to be reused.Heterogeneous photocatalysis is green,economic and effective.Therefore,on the basis of our previous work on heterogeneous photocatalysis,we studied the synthesis of acetals using heterogeneous photocatalytic methods.This thesis consists of four chapters.The first chapter mainly summarizes the progress of the synthesis of acetals.In this chapter,according to the different reaction conditions of acetal synthesis,the progress of acetal synthesis was reviewed in three parts,and the significance of this thesis was introduced.In the second chapter,the synthesis of acetals by heterogeneous photocatalysis of Ag₃PO₄was introduced.Firstly,Ag₃PO₄photocatalyst was prepared and characterized by XRD,SEM,XPS and UV-Vis DRS.Then,the synthesis of acetal catalyzed by Ag₃PO₄was studied,including the optimization of reaction conditions,the application range of substrates,the cycle stability of photocatalyst and the mechanism of acetal synthesis reaction.The results showed that under the irradiation of Green LEDs,Ag₃PO₄as photocatalyst and Ag NO₃as oxidant,aliphatic aldehydes or aromatic aldehydes could react with methanol,ethylene glycol or 1,3-propanediol to obtain 49 kinds of acetals with good yield.In the third chapter,the synthesis of acetals by heterogeneous photocatalysis of Bi VO₄was introduced.Firstly,Bi VO₄photocatalyst was prepared and characterized by XRD,SEM,XPS and UV-Vis DRS.Then the reaction conditions were optimized,the scope of substrates and the cycle stability of catalyst were studied.The results showed that aliphatic aldehydes or aromatic aldehydes could react with methanol,ethylene glycol or 1,3-propanediol to obtain 41 acetals under the condition of green light irradiation,Bi VO₄as photocatalyst and Ag NO₃as oxidant,but the yield was lower than that of Ag₃PO₄.In chapter 4,the experimental instruments,reagents and spectral data of the main compounds involved in this paper were introduced.In conclusion,synthesis of acetal using heterogeneous photocatalytic method was investigated in this thesis,and it demonstrates that both Ag₃PO₄and Bi VO₄photocatalysts are efficient for the reaction,thus two new,green,mild and cost-effective heterogeneous photocatalytic methods for the synthesis of acetal are provided.The application of heterogeneous photocatalytic methods in organic synthesis was further expanded.