The Synthesis And Technology Of Pentoxazone

Pentoxazone is a novel oxazolidinedione; it has a strong herbicidal effect on one-year-old barnyard grass and many broad weeds.According to concerned papers, we have designed a way to synthesize penxoxazone. It was prerared by cyclic reaction of N-(4-chloro-5-cyclopentyloxy-2- flourophenyl) carbamate with ethyl 2-hydroxy -3-methyl-3-butenoate under heating. This paper makes further research into its technology through single factor experiment and orthogonal experiments, thus obtain better synthesizing conditions. The optimum reaction conditions for the way are as follows: The ratio of N-(4- chloro-5-cyclopentyloxy-2-flourophenyl) carbamate and ethyl-2-yhdroxy-3-methyl -3-butenoate is 1: 3; reaction temperature is 200℃; reaction time is 3 hours, and the tributylamine was added after the ethyl 2-yhdroxy-3-methyl-3-butenoate introduced.In addition, we have discussed the synthesis of N-(4-chloro-5-cyclopentyloxy-2- flourophenyl) carbamate in the paper, it can be synthesized from 5-nitro-2-chloro-4- fluorophenol as a starting material by successive reactions such as catalytic hydrogenation and alkylation etc.. The influence of reaction temperature, reaction pressure and the catalyst on hydrogenation is studied by orthogonal experiments. The study shows that the optimum condition is as follows: reaction temperature is 100℃, reaction pressure is 2MPa, the catalyst is 1.8g and the solevent is 115mL.We also discussed the synthesis of ethyl 2-yhdroxy-3- methyl -3-butenoate; it is prepared by Darzens reaction of actone with ethyl chloroacetate in the presence of an catalyst. We make an optimum condition: reaction temperature 0～5℃, isomerization temperature was 125℃, and heat-preservation time 1h.All the structures of pentoxazone and its intermediates are characterized by IR, ~1H-NMR and MS.