The Application Of Triphenylphosphine Oxide In The Systhesis Of Carboxylic Ester

Organic phosphine compounds are widely used in organic synthesis.They are commonly used as catalysts for reaction or metal ligands to participate in reactions,such as Wittig,Appel,Staudinger and Mitsunobu reactions.Triphenylphosphine is an organophosphorus reagent that commonly used.The reaction conditions are mild and the yield is high when use this catalytic agent,but in the end of reaction,triphenylphosphine was oxidized into triphenylphosphine oxide by-product which lost the catalytic effect.In industry,choosing an appropriate reducing agent to reduce triphenylphosphine oxide and catalyze this reaction again is a common method,but the cost is high.By looking up the literature,we found that many of the phosphine oxide by-products can also be used as a catalyst or inhibitor for specific reactions.In order to reduce the cost and optimize the operation,we used the industrial by-product firstly,triphenylphosphine oxide as the coupling agent,to promote the esterification between carboxylic acid and alcohol.A newly activation system of“triphenylphosphine oxide with oxalyl chloride”was constructed,which was successfully applied to esterification of carboxylic acid with alcohols.This system has short reaction time,high yield,mild reaction conditions,and the reaction mechanism was tracked by ³¹P NMR.In addition,in order to facilitate the purification and recycle the coupling agent,this paper adopts two step synthesis method to prepare the immobilized triphenylphosphine oxide:the diphenyl?p-tolyl?phosphine was oxidized into?4-carboxyphenyl?phenyl-phosphine oxide by mineral chameleon under alkaline conditions;put the treated titanium dioxide?drying in vacuum,amination?with?4-carboxyphenyl?phenyl-phosphine oxide to amidation in“triphenylphosphine oxide with oxalyl chloride”system and prepare the immobilized triphenylphosphine oxide.The immobilized triphenylphosphine oxide was used in esterification,which had better coupling effect and recovery.