Acetylenic Grass Ester Synthesis And Process Research

Clodinafop-propargyl (Propynyl (R)-2-[4-[(5-chloro-3-fluoro-2-pyridinyl)oxy] phenoxy]propanoate) is a new kind of chiral, fluorinated and aryloxyphenoxypro-pionates herbicide. It is highly effective with a few quantities and will be well metabolized. It was firstly used in Switzerland, the South Africa and Chile and has been put into use in more than 50 countries, but there is not any report about its broad production and use in our country except for a few similar synthesis technologies. According to a commission of certain corporation, we will confirm the better synthesis methods and technical routes of clodinafop-propargyl and hope that the experiments could be magnified for industrialized production.This article is mainly about the preparation of clodinafop-propargyl, R-(+)-2-(4-hydrophenoxy) propionic acid, 2,3,5-trichloropyridine and 5-chloro-2,3-difluoropyridine. Though the comparison of each synthesis route, the optimum one is adopted, which might be put into industrial use.Clodinafop-propargyl is prepared from R-(+)-2-(4-hydrophenoxy) propionic acid, 2,3,5-trichloropyridine and propargly chloride. During the preparation, the molar ratio of reaction materials, the catalyst and the reaction temperature are all discussed. The best route is: DMF as the solvent, K₂CO₃ keeping the reaction mixture pH 8-10, n (5-chloro-2,3- difluoropyridine) : n (R-(+)-2-(4-hydrophenoxy) propionic acid) : n (propargyl chloride) =1 : 1.1 :2, the reaction temperature 70-75℃and the reaction time 10 h. The final product is gained by filtration, washing and recrystallization.During the preparation of R-(+)-2-(4-hydrophenoxy) propionic acid, the reaction environments, the alkali agent, the solvents and the conditions of purification are firstly discussed to confirm the basic reaction conditions; and then, an orthogonal experiment is designed for the best synthesis method: in the closed environment full of nitrogen, water as the solvents, NaOH as the alkali agent, n(hydroquinone) : n(S-(-)-2-chloropropionic acid)=1.2 : 1,n(hydroquinone) : n(NaOH)=1.5 : 1,the reaction temperature 50℃, the reaction time 6 h. The pure product is obtained through extraction by MiBK, washing with water solution of KOH and NaHSO₃ and acidification with strong hydrochloric acid.The preparation of 2,3,5-trichloropyridine includes two procedures: the addition reaction of trichloroacetaldehyde with acrylonitrile and the cyclisation of 2,4,4-trichloro-4-formyl butyronitrile. Three different methods are compared from the solvent, the molar ratio of reaction materials, the catalyst, the reaction temperature and time, and finally the best route is confirmed.During the preparation of 5-chloro-2,3- difiuoropyridine, two different methods are adopted to compare their advantages and disadvantages. And last ,the optimum one is confirmed.