The Catalytic Performance Of Pd/γ-Al₂O₃ In The Aminolysis Of Esters With Quaternary Ammonium Salts

Amides play a vital role in the synthesis of active intermediates in organic and pharmaceutical chemistry.In this paper,supported palladium nanoparticles catalysts were prepared by the impregnation reduction method（IR）using L-lysine as protection agent and Na BH₄ as reducing agent.We examined the catalytic performance of the catalyst under different conditions for the aminolysis of aryl esters using quaternary ammonium salts as amine source.The structure of the catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）,N₂ adsorption-desorption,atomic absorption spectroscopy（AAS）and X-ray photoelectron spectroscopy（XPS）to study the influence of different synthesis conditions on the performance of catalysts.The results revealed that the addition of L-lysine during the preparation process protects Pd NPs against agglomeration.The catalyst had a good performance for the aminolysis of aryl esters with quaternary ammonium salts.The results revealed that particle size of Pd NPs is the key factor to affect the catalytic performance of catalyst for the aminolysis of aryl esters with quaternary ammonium salts.Catalyzed by supported palladium nanoparticles,an aminolysis reaction between various aryl esters and quaternary ammonium salts has been developed for selectively synthesis of amides.Perfluorophenyl furan-2-carboxylate with tetrabutylammonium iodide was used as the model reaction.The catalyst had a good performance with the conversion ofperfluorophenyl furan-2-carboxylate was 88% and the yield of N,N-dibutylfuran-2-carboxamide was 87% in chlorobenzene at 120 o C for 24 h.The influence of supports,catalyst amount,solvent,palladium loading and reaction temperature were investigated.In addition,the catalyst can be readily recovered and reused for five cycles with 25% decline of activity after the 5th recycle.A broad scope of aryl esters could react with quaternary ammonium salts to synthesize the corresponding amide in moderate to good yields.Meanwhile,electron-withdrawing groups in either the alkyl part or the acyl part of the esters are more beneficial for this reaction.Based on relative literatures and our results,a tentative mechanism was proposed.