Method for preparing diethyl methyl-phosphonite

The invention provides a method for synthesizing diethyl methyl-phosphonite. The method comprises technological steps as follows: firstly, a ternary complex is prepared from phosphorus trichloride, aluminium trichloride and chloromethane as raw materials, the ternary complex is reduced by powdered aluminium and reacts with absolute ethyl alcohol, a crude diethyl methyl-phosphonite product is obtained and subjected to reduced-pressure distillation, and a pure product is obtained. According to the method, diethyl methyl-phosphonite is directly prepared from the ternary complex, an intermediate methyl phosphonic dichloride is not needed, and dangerous level of industrial production is reduced; compared with a traditional technology for preparing diethyl methyl-phosphonite from the intermediate methyl phosphonic dichloride, ethyl alcohol and sodium chloride through a reaction, the reaction conditions are milder, waste residue rate is obviously reduced, and yield is as high as 85%. 本发明提出了种甲基亚膦酸二乙酯的合成方法，其工艺步骤如下：先以三