Chemical Synthesis Of Sesamol

3,4-methylenedioxyphenol (namely sesamol) is a superior low-toxicity antioxidant and an important medicine intermediate. Among sesamol's process technologies, extraction from sesame oil or semi-synthesis from piperonal via oxidation and hydrolysis has been limited by the requirement of natural resources protection, which makes the development of the synthetic technology from cheaper petrochemicals a hotspot in the field. In this paper, with 1,3-benzodioxole (EDO) synthesized from catechol as the starting material, the four-step process to prepare sesamol was studied, which was nitration, hydrogenation, diazotization and hydrolysis. At the same time, the optimal process conditions and methods for purifying the product and recycling CuSO4 were also presented. The product was confirmed by m.p. measure, element analysis, IR, MS and GC.During the nitration of 1,3-benzodioxole, the effect of HNO3 dosage, reaction temperature, reaction time on the yield of l,2-methylenedioxy-4-nitrobenzene (MDNB) was studied, while the nitration mechanism was preliminarily proved. The optimal reaction conditions are as follows: HNO3:BDO=2.5:l(mol/mol); dilute HNO3: BDO=12:1(v/v); the dropping time of BDO is 40~50min , and at this time the temperature of dilute HNO3 is 60~70C; the reaction is continued for 2h at 90C after completion of adding BDO. Under these conditions the yield can reach 97%.In the atmospheric liquid-phase hydrogenation of MDNB, Raney Ni shows excellent catalytic activity, compared with reduced Ni, amorphous NiB and amorphous NiB/SiO2. The effect of Raney Ni dosage, reaction temperature, ethanol dosage and catalyst reuse on the hydrogenation time of MDNB was studied, and then the optimal process conditions were given: Raney Ni : ethanol : MDNB =0.15:8:1 (mass ratio); the reaction temperature is 40C; the reaction time is about 2.8h. In this way the yield of 3,4-(methylenedioxy)aniline(MDA) can come to 97.5%.As for the diazotization process of MDA, the method of instantly feeding HNO2 solution is adopted. Therein H2SO4:NaNO2:MDA=2.7:1.2:1 (molar ratio); the concentration of H2SO4 and NaNO2 is about 17% and 30 % respectively; the reaction temperature is controlled in the range from 3C to 4C; the reaction time is designed as 2h by the method of TLC.The hydrolysis system of diazo salt of MDA consists of water-phase and oil-phase. The effect of process parameters like feeding time, volume ratio of water-phase to oil-phase, H2SO4 concentration and Cu2O dosage on the yield of sesamol was thoroughly investigated. The optimal reaction conditions are as follows: H2O:98%H2SO4:CuSO4.10H2O:Cu2O:MDA=16:2.4:6.5:0.3:l(mass ratio); CH2Cl2 oil-phase : initial water-phase=2:l(v/v); the reaction temperature is 37.5C; the dropping time of fresh diazo salt is 3.5~4.0h; when alkaline p-naphthol shows the negative, the reaction is completed. 4% Na2CO3 solution is used to purify crude sesamol. During the purification process, the parameters such as Na2CO3 dosage, solubilization time and concentration of H2SO4 used for acidification were studied. The highest yield is obtained when Na2C03: crude product=1.5:l (wt/wt), solubilizing crude product for 3~5min under 10-15 C, acidifying the solution of sodium salt to pH=l by 20% H2S04. After the product is recrystallized from petroleum ether, its yield attains 70.1% (based on MDA) with the purity of 99.48%, and the total yield is 66.3%. The method of conversion and circulation was introduced to recycle CuSO4 in hydrolysis system. The procedure is : first, CuSO4 is changed into CuO through Cu(OH)2; then, CuO is separated from the hydrolysis system; finally, pure CuSO4 is regained by reacting between H2SO4 and CuO. The recovery can reach 100%.