Study on octenes alkoxycarbonylation to methyl n-nonanoates catalyzed by palladium
Alkoxycarbonylation reaction is an important method for the one-step synthesis of high-value ester products,which has important applications in the field of fine chemicals.However,the reaction rate of medium-and long-chain olefins is low,and the industrial production applications often face difficulties such as high cost,poor product selectivity and easy decomposition of catalysts.Novel catalytic systems were used to convert endo-or terminal-octenes to methyl n-nonanoates by alkoxycarbonylation.The influence of phosphine ligands,catalysts,temperatures,pressures,alcohols and different olefins on the alkoxycarbonylation of octenes were investigated,respectively.Combined with the analysis results,the reaction mechanism of octene alkoxycarbonylation was explained.The results show that the introduction of asymmetric bisphosphine ligands(L8)containing ferrocene skeleton into the reaction system has good catalytic activity and product selectivity.And under the optimal reaction conditions(130 ℃,4 MPa,0.1 mol 1-octene,5.0 mmol p-toluenesulfonic acid,0.1 mmol Pd(acac)2,0.3 mmol phosphine ligand L8 and reaction for 15 h),the reaction shows the best activity.At the moment,conversion rate of 1-octene,yield of methyl nonanoates and molar ratio of stereomers and isomers methyl nonanoates are 99％,99％and 17.2,respectively.Compared with other ligands,the ferrocene moiety in the phosphine ligand L8 has unique electronic properties,which can influence the electronic effect of the phosphine ligand by adjusting the electron cloud density,thus optimizing the electronic state of the metal center and improving the activity and product selectivity of the catalysts.In addition,the rigidity of the ferrocene backbone helps the ligands to maintain a specific spatial site resistance during the coordination process,contributing to the improved product selectivity of alkoxycarbonylation of medium-and long-chain olefins.
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