中试规模生产除草剂苯嗪草酮

The Process Improvement in the Scale-Up Synthesis of Herbicide Metamitron

研究了除草剂苯嗪草酮的生产工艺.以草酸二甲酯为原料,甲醇为溶剂,与碳酸钾反应得到中间体1,产率为97%.再以苯为溶剂,将中间体1与三光气加热回流反应5 h得混合液,然后以三氯化铝作为催化剂,混合液与苯发生Friedel-Crafts酰基化得中间体2,两步总产率为71.1%.再以乙醇为溶剂,将中间体2与乙酰肼发生缩合反应,制得中间体3,产率为90%.然后,以冰醋酸为催化剂,将中间体3与水合肼反应得中间体4,产率为93%.最后以正丁醇为溶剂,将中间体4与乙酸钠脱水环化得苯嗪草酮,收率为83.4%.苯嗪草酮的总收率为48.1%,液相纯度为99.30%.其结构经1H NMR确证.

The synthetic process of Herbicide Metamitron was studied. Intermediate I was synthesized in 97% by the reaction of dimethyl oxalate with potassium carbonate in the presence of concentrate methanol as solvent. 1 reacted with the three phosgene at dehydration condition for 5 h in the presence of beneze to prepare mixture. Then mixture reacted with benze for Friedel-Crafts acetoxylation to give intermediate 2 in the presence of Aluminum trichloride as catalyst. The two steps yield was 71.1%. 2 reacted with acetyl hydrazine for condensation in the ethanol to give 3 in 90% yield. Intermediate 4 in 93% yield was prepared by 3 and hydrazine in the presence of acetic acid as catalyst. Finally, in the presence of butylalcohol, the reaction of 4 with sodium acetate for dehydration cyclization to obtain metamitron. Yield：83.4% ,HPLC purity：99.30%. The total yield of the title product was 48.1%. The structures of metamitron was confirmed by 1H NMR.