cis-DL-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid

(±) cis-permethrin acid can be adjusted to a certain value by adding (±) cis-trans-permethrin acid to sodium hydroxide solution, and then carbon dioxide is passed through the solution, (±) cis-permethrin acid precipitates , Filtered and dried to obtain (±) cis-permethrin acid, which contains (±) trans-permethrin in its mother liquor to prepare trans-cypermethrin. In addition, 3, 3-dimethyl-4, 6, 6, 6-tetrachlorohexanoic acid ethyl ester can be produced by the telomerization reaction of methyl bentinate and carbon tetrachloride, and then cyclized with potassium tert-butoxide (±)methyl permethrin is produced with a cis-inverse ratio of 9:1, and then further saponified and recrystallized to obtain (±)cis-permethrin. The process is as follows: add ethyl 3, 3-dimethyl-4-pentenoate, carbon tetrachloride and benzoyl peroxide in a round bottom flask, reflux for 24h under nitrogen protection, and then distill the tetrachloride Carbon, the reaction residue is washed with dilute NaHCO3 solution to weakly alkaline, then washed with saturated brine to neutral, dried, concentrated and distilled under reduced pressure to obtain 3, 3-dimethyl-4, 6, 6, 6-tetrachlorohexane Ethyl acid, the yield can reach 90%, the boiling point is 115～116℃/27Pa. In addition, put anhydrous tert-butanol into a round bottom flask, put potassium metal under the protection of nitrogen, heat to reflux until all potassium metal is dissolved, cool to room temperature, add cyclohexane and dimethylacetamide mixed solvent, stir well, and cool To -20°C, add 3, 3-dimethyl-4, 6, 6, 6-tetrachlorohexanoate ethyl ester and tert-butanol mixture dropwise to the solution. After the addition, it will be at -20～- React at 15°C for 5 hours, then warm to room temperature for 1 hour, add saturated ammonium chloride solution, separate the organic phase, wash with saturated brine until neutral, dry and concentrate, and distill under reduced pressure to obtain rich cis-permethrin. , The inverse ratio is 9:1, and the boiling range is 91～93℃/20Pa. Then, the above-mentioned rich cis-permethrin acid was added to the ethanol aqueous solution with potassium hydroxide, heated to reflux for 5 hours, saponified, and evaporated most of the ethanol and water under reduced pressure. Under ice-bath cooling, it was acidified with 30% HCl to precipitate light. The yellow solid was filtered, dried, and recrystallized with n-hexane to obtain (±) cis-chrysanthemic acid as a white solid.

(±) Cis-permethrin is an intermediate for the preparation of cypermethrin, cis-cypermethrin, and deltamethrin.