Study On Esterification Of Phenols Under Solvent-Free Condition

The esterification of phenols is the most fundamental transformation in organic synthesis and it is widely applied in industrial production of useful intermediates. Despite a number of precedents, new efficient methodologies for acylation are still in demand.An important goal in organic synthesis is to develop greener approaches and more economically competitive pathways. Solvent-free organic reactions make organic synthesis simpler, saving energy, minimizing wastage, avoiding the using of toxic organic solvents, reducing environmental pollution, and the reactions occur in mild conditions, usually require easier operating procedures and simpler apparatus. In view of these, esterification of phenols in solvent-free conditions has become an important and popular field of study.In this thesis, esterification of phenol with acetic anhydride, maleic anhydride, phthalic anhydride were studied separately under solvent-free conditions.Phenyl acetyl and its derivatives were obtained by acetylation of phenols in the absence of solvent, under microwave irradiation,with solid bases as catalysts. First of all, several new catalysts were prepared, which were made in impregnation and microwave radiation method with several common solid bases loaded in alumina. The solid bases loaded and unloaded in alumina as catalysts were used in the solvent-free acetylation of phenol. The results showed potassium carbonate-alumina (solid baseⅢ-3) has best catalysis. Optimizing the conditions of acetylation of phenol with solid baseⅢ-3, the results showed that catalyst molar percent to phenol was 16.8mol%, reaction temperature was 60℃, with the yield of 94.8%. Acetylation of substituted phenols had been studied with solid baseⅢ-3 under solvent-free conditions. The effect of conventional heating and microwave heating were studied separately in the reactions. Experimental data showed that microwave heating was feasible and effective in acetylation of phenols under solvent-free conditions.The esterification of phenols with maleic anhydride were studied using solid bases as catalysts, under solvent-free conditions.Butenedioic acid monophenyl ester and its derivatives were synthesized. The study investigated two kinds of catalysts: solid acids and solid bases. The results showed that Na2CO3,NaHCO3,NaOH especially Na2CO3 were good catalysts but the solid acids were't good catalysts in the reaction. The conditions of the esterification of phenol with maleic anhydride were optimized. Then esterification of substituted phenols with maleic anhydride were studied with Na2CO3 under solvent-free conditions and the experimental data showed that the yields were 25.9%-79.4%.The esterification of phenols with phthalic anhydride were studied under solvent-free conditions, using solid base catalysts, and single phenyl phthalate and derivatives were synthesized. The catalysts were investigated in the experiment, the results showed that Na2CO3 was the best catalyst in these solid bases. The conditions of the esterification of phenol with phthalic anhydride were optimized, then esterification of substituted phenols with phthalic anhydride were studied with Na2CO3 under solvent-free conditions and the experimental data showed that the yields were 65.7%-89.5%.All products were characterized by IR and NMR. The materials and solid base catalysts are cheap, easy to achieve. Solvent-free synthesis is green and environment-friendly pathway.