Microwave-assisted Synthesis Of Natural Phytoestrogen Isoflavones

Based on research status,the microwave-assisted catalytic technology on isoflavonoids was used for the purpose of efficient,low power,continuous production.In this paper,the reaction mechanism of isoflavones under microwave irradiation was investigated to determine the reaction controlsteps,eastablish the kinetic model,calculate and verify the rationality of the model.Firstly,the“reaction-separation-reaction" coupling system was applied to synthesize important intermediates deoxybenzoin,to make the reaction system with good continuity of process controllable,effectively reduce energy consumption and pollutant emissions,and easy to operate.Secondly,for the first time,the DMSO was emploied as solvent in which the yield had more than in other solvent.The impact factors of synthesis of 4',7-dimethoxyisoflavone was investigated,which triethyl orthoformate was used as starting material in the reaction of carbon cyclization,through quadratic regression orthogonal composite experimental and analysis of variance,the mathematical model of relationship between factor xi and yield y of 4',7-methoxyisoflavone was established,the optimal value of each factor xi was obtained by the mathematical model y extremum.Thus,the yield of 4',7-methoxyisoflavone is more than 92.96%with purity of 97%and the reaction time is reduced six-fold under microwave condition.Stable amplification experiments showed that the reaction was stable after the regression orthogonal optimization process,the crude product of cyclization can be directly used for next step without refining.Thirdly,the factors of demethylation of 4',7-methoxyisoflavone and dynamics equations were investigated under microwave-assisted catalytic condition.The result of experiment showed that microwave power,the initial concentration of substrate and the reaction temperature is more significant on reaction rate.When the microwave power was at 800 W,the initial concentration of substrate was 0.88 mmol/L at 125?temperature,the reaction kinetic of reaction of 4',7-methoxy isoflavone demethylation was studied to establish the kinetic equation.The apparent activation energy Ea is 87.68 KJ/mol and the pre-exponential factor A is 4.91 ×109 min-1.The impact of various factors on the reaction was discussed.Comparing different microwave power and under normal conditions,the activation energy Ea and refers to changes in the pre-exponential factor A is found,and the relationship between microwave power and the pre-exponential factor is obtained by fitting equation,the microwave power the greater,the intermolecular collision probability increases.The target product is a white solid with purity of 96.18%and yield of 83.98%.Finally,on the basis of microwave-assisted systhsis method of 4',7-dihydroxyisoflavone,a series of isoflavonoids was synthesized,which included 3',4',7-trimethoxyisoflavone(purity 98.69%,yield 92.68%),3',4',7-trihydroxyisoflavone(purity 99.41%,yield 86.36%)and its derivatives,4',5,7-trimethoxyisoflavone(purity 96.39%,yield 91.89%),4',5,7-trihydro xyisoflavone(purity 98.82%,yield 83.09%)and its derivatives,3',4',5,7-tetramethoxyisoflavones(purity 94.09%,yield 90.19%),3',4',5,7-tetrahydroxyisoflavones(purity 98.41%,yield 82.15%).All of the structure of products were confirmed by HPLC,IR,1H-NMR,EI-MS and other qualitative and quantitative analysis in this paper.