Esterification or transesterification reactions are usually carried out in the presence of homogeneous or heterogeneous catalysts.However,recently a new method was reported for the esterification of carboxylic acids by tributyl borate under solvent- and catalyst-free conditions.In order to show the synthetic ability of trialkyl borate esters in the esterification reactions,here,the esterification of other carboxylic acids and diacids by tributyl-,triisoamyl-,and tribenzyl borate under the same conditions were reported.Some of the prepared ester and diester products have found wide applications as plasticizers and synthetic ester base lubricants.The esterification reactions have been cleanly carried out in the absence of any solvent under catalyst-free conditions.The maximum rate belongs to isoamyl trichloroacetate (Ⅵb) which reached about 76% within about 6.5 h.On the basis of obtained findings,it seems that electron withdrawing groups on carboxylic acid facilitate the esterification reaction.
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