The Study Of Synthesis Of Diethyl Malonate In One-pot Carbonylation

Diethyl malonate(DEM) is an important organic intermediate which is widely used in the production of organic industial and has extensive potential in various industial applications. This paper give the summary on the synthesis methods of DEM. At present, the main industrial synthesis of DEM is still in the traditional method (NaCN route), which is completed through the process of cyaniding, neutralize, hydrolytic reation and esterification. But, for the disadvantage of low yields, serious pollution and high cost for use of NaCN and malonic acid, the NaCN route is urgently awaiting to be improved. In the recent years, the novel method of carbonylation has great advantage for the green production and low cost, based on the two-step carbonylation method, we propose the One-pot catalyzed carbonylation for synthesis of diethyl malonate. This method take ethyl chloroacetate, ethanol, carbon monoxide and the catalyst of cobalt salt as raw materials with low cost and high catalytic efficiency; besides, the process is completed by one step of material feeding, it would be a great breakthrough in the field of carbonylation for the simple reaction process, little reaction time and high yields.This paper discusses the effection of Na2S2O4 on the One-pot catalyzed carbonylation synthesis of DEM, and it is compared with the two-step method synthesis of DEM to prove the superiority. In this experiment, we don’t need any Na2S2O4 and take four kinds of cobalt salt such as CoCl2·6H2O, Co(CH3COO)2·6H2O, CoSO4·7H2O and Co(NO3)2·4H2O as the catalyst, and then the corresponding metal activator system and the alkaline systerm for each cobalt salt are studied, further more, the optimum ratio of raw materials and the best reaction condition are determined. At last, the economical benefit and the social benefit is also analyzed to ensure the industial process feasibility.(1) In two-step method synthesis of DEM, Na2S2O4 has great impact on the yield, instead, in one-pot catalyzed carbonylation, the best yield of DEM is obtained for 100% when the Na2S2O4 is not added.(2)The performance of cobalt salt catalysts were compared through the yield of DEM, the main results are as follows:COSO4·7H2O exhibit higher activity at lower mole ratio of CoSO4·7H2O and chlorinated ethyl acetate followed by CoCl2·6H2O and Co(CH3COO)2·6H2O, and the Co(NO3)2·4H2O perform the worst activity of all.(3) Such metal activator as Zn, U-Fe and Fe present some activity, the active order of different metal activators is as follows:Zn>U-Fe>Fe. Besides, the choice of alkaline system is different for different cobalt salt system. Of which, CoSO4·7H2O and Co(NO3)2·4H2O present high catalytic effect in high alkaline environment of NaOH. in contrary, CoCl2’6H2O and Co(CH3COO)2·6H2O with good effect in low alkaline environment of K2CQ3 and NaHCO3.(4) The optimum reaction conditions of One-pot catalyzed carbonylation for synthesis of diethyl malonates were investigated:the yield of dethyl malonate can reach 100% on the conditions of 1.0～1.5MPa CO pressure, 60～70℃ reaction temperature,4h reaction time, and the raw material mole ratio of COCl2·6H2O, Co(CH3COO)2·6H2O:ethyl chloroacetate is 0.16～0.2 or the raw material mole ratio of CoSO4·7H2O, Co(NO3)2·4H2O:ethyl chloroacetate is 0.05～0.1, Zn:cobalt salt=2:1, alkali:chlorinated ethyl acetate=1:1, ethanol: chlorinated ethyl acetate=13.7:1.(5) After the analysis of raw materials and technological process, the result indicates that this method with good economic efficiency, social efficiency and environment efficiency.In a word, the new simple method of one-pot catalyzed carbonylation has many advantages for low cost, short reaction time, high selectivity and yields, mild reaction condition, environmental friendliness and the atom economy.