Synthesis and Process of Diethyl 2-(2,4,6-Trimethylbenzylidene)malonat

Diethyl 2-(2,4,6-trimethylbenzylidene)malonat was the key intermediate of herbicide Tralkoxydim.The synthesis with low yield was reported in a previous study.Here,the new process and the influences of factors on the yield were studied,such as the kinds and the quantity of catalyst,reaction time,the ratio of raw material and the time of azeotropic dehydration.[Results] The results showed that the optimum reaction conditions were obtained as follow: piperidine as catalyst,n(mesitaldehyde):n(piperidine):n(diethylmalonate) =1:1:1.5,refluxing time 4 h,azeotropic dehydration time 4 h.The yield reached up to 97.7%(based on mesitaldehyde) under the optimum reaction conditions.The structure was confirmed by IR,1H NMR and elemental analysis.[Conclusions] Under the optimum reaction conditions,diethyl 2-(2,4,6-trimethylbenzylidene)malonat was gained higher yield by Knoevenagel condensation using mesitaldehyde and diethylmalonate in presence of piperidine.