Research On Catalytic Synthesis Of Vinyl Esters Compounds

Vinyl esters are one kind of vital industrial materials whose polymer product are widely applied to biodegradable biomaterials such as surgical sutures and coatings,adhesives and inks.As an important derivative of vinyl esters,vinyl benzoate is mainly synthesized by the addition of benzoic and acetylene,however,it requires harsh reaction conditions and high cost of raw materials leads to high price of vinyl benzoates.On the other hand,vinyl esters can also been synthesized by the oxidation of ethene and benzoic which should be paid attention to the explosion limit,lead to the increased production difficulty.So the vinyl transfer method was applied to synthesize vinyl benzoate due to its mild reaction conditions and low cost of raw materials.Vinyl transfer reactions are always catalyzed by noble elements such as Pd(II)and Au(I).Since these ligand-contained homogeneous catalysts require the protection of inert gas and afford the unsatisfied yields,there are certain limitations in the application.In order to reduce the production difficulty and increase the catalytic efficiency,this paper studied the synthesis of vinyl benzoate by transfervinylation reactions.Herein,we reported a high catalytic activity,recoverable,air-stable and less toxic Rh(III)catalyzed transvinylation reaction to synthesize the vinyl benzoates under the neat reaction conditions.In this study,we first report the rhodium catalysts can be applied to the vinyl transferreactions include RnCl3·3H2O,RhCl(PPh3)3,RhH(PPh3)3CO and Rh(CO2)acac.After the optimization of reaction conditions,vinyl benzoates can be synthesized by adding 2 mol%RhCl3·3H2O and sodium formate as additive to react for 24 hours under 80?.Compared to the palladium or gold catalysts,the RhCl3·3H2O afford the excellent yields of target product which up to 95%.By the way,since this catalyst system requires no additional ligands,it's air and water stable.On the other hand,the RhCl3·3H2O catalyst can still catalyze the vinyl transfer reaction of the carboxyl group with high selectivity under the interference of phenolic hydroxyl groups.In contrast,the RhC1(PPh3)3 catalyst affords the much more side product which the phenolic hydroxyl groups undergo a esterification.Besides,we have also researched the recycled ability of RhCl3·3H2O catalyst and the results show that the catalyst is recyclable in 4 consecutive runs.At last,we proposed a possible reaction mechanism based on the XPS spectrum of recycled rhodium catalyst and the results of experiments which tend to explore the effects of chloride ion and sodium formate,this can provide theoretical support for further research.