Synthesis of Lambda Cyhalotric Acid

Lambda Cyhalotric Acid is a white to off-white solid powder under ambient conditions, characterized by its distinct acidity and excellent chemical stability. As a key shared intermediate for several pyrethroid varieties, Lambda Cyhalotric Acid is extensively utilized in the synthesis of a range of insecticides including tetramethrin, methothrin, permethrin, valerate, fenvalerate, cypermethrin, and tefluthrin. Furthermore, this compound serves as a versatile intermediate in the pharmaceutical and agrochemical industries, and is also employed in scientific research and laboratory settings.

Figure1 Picture of Lambda Cyhalotric Acid

Synthesis

Method 1

A study has reported a synthetic method for Lambda Cyhalotric Acid, which comprises the following steps: under an oxygen-free environment, adding cis-3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate into a mixed solvent system composed of an alcohol, dimethylformamide, and an alkane, then cooling the mixture to 15–5°C and introducing a tert-butanol suspension containing tert-butoxide to form the reaction system. When the content of Lambda Cyhalotric Acid in the reaction system falls below 0.5%, desolvation is performed to obtain a mixed liquid, which subsequently undergoes saponification, acidification, and purification to yield the high-cis cyhalotric acid. This synthetic approach not only reduces synthesis time and cost but also simplifies operational procedures, resulting in higher post-reaction yields and superior product quality, thereby enhancing the utilization efficiency of raw and auxiliary materials in industrial production while reducing waste treatment and discharge costs, making it well-suited for large-scale industrial manufacturing. [1]

Method 2

A study has reported a method for synthesizing Lambda Cyhalotric Acid using a loop reactor, characterized by the following steps: (1) methyl 3,3-dimethyl-4-pentenoate and 1,1,1-trifluorotrichloroethane are used as raw materials to react in a tert-butanol solution with copper(I) chloride and monoethanolamine as catalysts to form an adduct; (2) in the loop reactor, the adduct undergoes cyclization and dehydrochlorination with the catalyst in a mixed solvent of tert-butanol and DMF to generate a cyclized product; (3) the cyclized product undergoes saponification and elimination with liquid caustic soda, followed by continuous acidification to prepare cyhalothric acid, which is finally subjected to double recrystallization to obtain highly pure Lambda Cyhalotric Acid. [2]

Cyhalotric acid wastewater treatment

The washing and acidification steps involved in the saponification and acidification reactions of Lambda Cyhalotric Acid require substantial amounts of water or dilute acid to wash the reaction products, consequently generating large volumes of organic wastewater containing salts. This wastewater exhibits complex composition, high concentration, and elevated chromaticity, making it difficult to treat. The organic substances present are predominantly unsaturated compounds containing fluorine or chlorine, which are resistant to biodegradation and may even possess biological toxicity. These characteristics preclude the use of conventional treatment methods such as coagulation sedimentation or biological processes, thereby presenting significant treatment challenges. The present invention discloses a treatment method for Lambda Cyhalotric Acid wastewater, characterized by the following steps: adding an alcohol solvent to the wastewater for thorough extraction, allowing phase separation, adjusting the aqueous layer to neutrality followed by dehydration and desalination using MVR, and recovering the organic layer through reduced-pressure distillation. This invention offers a simple treatment process suitable for industrial-scale implementation, substantially reducing wastewater generation and lowering the COD content of high-concentration wastewater, thereby reducing production costs. [3]

Conversion to Acid Chloride

The present invention discloses a method for preparing cyhalothryl chloride, which comprises adding Lambda Cyhalotric Acid, phosphorus pentachloride, and phosphorus oxychloride into a reaction apparatus, heating the mixture to 50–85 °C, and maintaining this temperature for a reaction period of 1 to 20 hours. Upon completion of the reaction, cyhalothryl chloride is obtained by reduced-pressure distillation. In this process, Lambda Cyhalotric Acid and phosphorus pentachloride are used in a molar ratio ranging from 1:1 to 1:3, while the weight ratio of Lambda Cyhalotric Acid to phosphorus oxychloride is between 1:1 and 1:50. The distillation is carried out at a temperature of 45–85 °C under a pressure of 0.85–0.95 MPa, and hydrogen chloride gas generated during the reaction is absorbed using a falling film absorber. Since the only gaseous by-product formed in this method is hydrogen chloride, it can be directly absorbed with water, resulting in no environmental pollution; moreover, the hydrochloric acid produced can be sold, thereby increasing the overall utilization value and reducing production costs. The post-treatment of the invented method is straightforward, requiring only reduced-pressure distillation to obtain the target product with high purity, making it well-suited for industrial-scale production. [4]

Reference

[1] KANG S. D. et al. A synthetic method of high-cis cyhalotric acid, Chinese patent, Patent Number:CN202211181247.9[P].

[2] MAO J. S. Method for synthesizing cyhalotric acid using loop reactor, Chinese patent, Patent Number:CN201610353837.3[P].

[3] MA M. C., JIN G. L., BAO R. S., et al. Method for treating cyhalotric acid wastewater, Chinese patent, Patent Number:CN202110540187.4[P].

[4] KONG F. L. Method for preparing cyhalothryl chloride, Chinese patent, Patent Number:CN201310383506[P].

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