Study On Oxonium Ion Mediated Carbonyl-olefin Metathesis

The construction of carbon-carbon double bonds is of great value for the synthesis of many biologically active molecules,drugs and natural products.The olefin-olefin metathesis reaction,which won the Nobel Prize in 2005,not only can achieve the extension of olefin carbon chains,but also can be used to construct cyclic molecules,and has been widely used in medicine,chemical industry,and other fields.Carbonyl group can be regarded as the precursor functional group of carbon-carbon double bond,so the metathesis reaction between unsaturated carbon-carbon bonds and carbonyl groups has also aroused great interest among chemists.Carbonyl and carbon-carbon double bonds are the most common functional groups.The olefin-carbonyl metathesis reaction has good application prospects,because it can directly construct new carbon-carbon double bonds between carbonyl and olefin groups,and provides an efficient path for the synthesis of complex cyclic molecules.In recent years,the olefine-carbonyl metathesis reaction has developed rapidly,but the research on this reaction is still in its early stages,and there are still many shortcomings and limitations,mainly including the narrow range of substrate scope,and the limitation of reaction in intramolecular version mainly.Therefore,further exploring the application range and catalytic system of this metathesis reaction has important research value.Current studies show that the olefin-carbonyl metathesis reaction is achieved through the[2+2]and inverse[2+2]reactions of carbonyl and carbon-carbon double bonds.Due to the weak electrophilicity of carbonyl groups and the weak nucleophilicity of olefins,this reaction is usually difficult to carry out,especially the intermolecular olefin-carbonyl metathesis.In this thesis,we use oxyonium ion generated in situ to activate carbonyl groups and enhance their electrophilicity,thus,an olefin-carbonyl metathesis reaction mediated by oxyonium ion is achieved.We firstly explored the feasibility and conditions of this metathesis reaction by using an intermolecular reaction.After a lot of experiment research,we have obtained the most suitable reaction conditions:using 20 mol%BF₃·OEt₂ as catalyst,120 mol%trimethyl orthoformate as additive,and CHCl₃ as solvent.Under this optimized reaction condition,the substrate universality of inter-and intramolecular metathesis reactions was studied,and a series of open-chain and cyclic olefins were synthesized in medium to good yields.In addition,the possible reaction mechanism was speculated.The research content of this thesis enriches the reaction system of olefin-carbonyl metathesis reaction,and expands its application range in organic synthesis.Furthermore,it also provides a fast way for the synthesis of some open-chain and complex cyclic olefin compounds.The method developed in this paper has the advantages of good yield and simple operation.Due to the impact of the epidemic,some of the content of the paper needs further in-depth research.