Permethrin is a synthetic insecticide belonging to pyrethroid compounds, which is a mixture of various high-efficiency acacia insecticides. It is composed of two pyrethroid molecules linked together. It is a broad-spectrum and high-efficiency insecticide, which is widely used in the protection of agricultural crops, household products, livestock and other fields. It can be prepared in a variety of ways, and five main synthetic methods will be introduced in this article.
Synthetic method one:
(1) Firstly, it is necessary to dechlorinate chloroform to generate cyclopropylmethane;
(2) Condensation reaction of cyclopropylmethane and ethyl 2,2-difluoroacetate to produce ethyl γ-bromopropionate;
(3) Ethyl γ-bromopropionate is added to cyanotetrahydrofuran for epoxidation reaction to generate oxidized cyclopropylpropionitrile;
(4) Add cyclopropylpropionitrile oxide and 3-phenylbenzaldehyde to sodium hydroxide and formaldehyde for condensation reaction to generate smooth chain permethrin;
(5) Add the smooth chain permethrin to hydrogen oxide for oxidation to generate permethrin with α-carbonyl.
This synthetic method is relatively simple, but the obtained product is impure.
Synthetic method two:
(1) Condensation reaction of ethyl 3-bromopropyl-2,2-difluoroacetate and cyclopropylene oxide to generate 2-(3-bromopropionyloxy)cyclopropyl-2,2-difluoroacetic acid ethyl ester;
(2) Ethyl 2-(3-bromopropionyloxy)cyclopropyl-2,2-difluoroacetate is added to cyanotetrahydrofuran for epoxidation reaction to generate oxidized cyclopropylpropionitrile;
(3) Add cyclopropylpropionitrile oxide and 3-phenylbenzaldehyde to sodium hydroxide and formaldehyde for condensation reaction to generate permethrin with δ-azido group;
(4) Hydrogenate permethrin with δ-azido to generate intermediates;
(5) Use cellulose proton exchange resin (CEX) for selective hydrolysis to eliminate the δ-azido group to obtain permethrin.
This synthesis method can get pure permethrin.
Synthetic method three:
(1) Condensing 2-chloro-3,3,3-trichloropropionic acid with 2,2-difluoroethanol to generate 2-chloro-3,3,3-trichloro-1-propanol;
(2) Addition reaction of 2-chloro-3,3,3-trichloro-1-propanol with hydrogen cyanide to generate 2-(cyanohydroxymethyl)-3,3,3-trichloro-1 - propanol;
(3) Add 2-(cyanohydroxymethyl)-3,3,3-trichloro-1-propanol into tetrahydrofuran to react with acetophenone to generate permetrin with cyclopropenone structure.
The advantage of this synthesis method is that the process is simple and the usage of chemical reagents is reduced.
Synthetic method four:
(1) Pass chlorine gas into nitrobenzene to generate chlorinated nitrobenzene;
(2) Condensation reaction of nitrobenzene chloride and epichlorohydrin in the presence of tri-tert-butyl alumina to generate double-substituted products;
(3) Add the double-substituted product and nicotinamide to the sulfuric acid drop for reaction to generate a dimethylol substrate;
(4) Perform a competitive chemical reaction between the dimethylol substrate and ethyl cyanide in the presence of ethanol to generate cypronitrile;
(5) Add cyclopropanenitrile and 3-phenylbenzaldehyde to sodium hydroxide and formaldehyde for condensation reaction to generate permethrin.
The advantage of this synthetic method is that the yield is high and there is no nitroso intermediate, but the reaction conditions are relatively harsh.
Synthesis method five:
(1) Mix ethyl 2,2-difluoroacetate, epichlorohydrin and chloroform, and add it to a perchloroalkane catalyst containing ammonia or tetrahydrofuran to generate tetrasubstituted acrylate;
(2) Add tetra-substituted acrylate to boric acid undecyl ester catalyst for ring closure reaction to generate permethrin;
(3) Perform random migration of permethrin and add hydrogen oxide and formic acid to generate permethrin with α-carbonyl.
The advantages of this synthetic method are good atom economy, high yield, low operating temperature and excellent regioselectivity.
In summary, there are many methods for the preparation of permethrin, among which the second and fifth methods are the best, with high product purity and simple reaction conditions, which are suitable for large-scale synthesis. In addition, for each method, its advantages, disadvantages and important characteristics also need to be considered to select the method suitable for the specific application.
Permethrin is a synthetic organic ingredient that belongs to the class of bacterial toxins (pyrethroid). It is a fat-soluble organic compound and is a UV-stabilized ingredient. The compound comes in the form of chloroboron fluoride or oxygen protectant and has strong action and good effect. Permethrin is widely used to treat mites, scorpions, ants, spiders, leeches, mosquitoes and other pests, and is also used to protect crops.
The discovery of permethrin is of great significance to the protection of crops and public health. In the early 1960s, the large-scale poisoning caused by organophosphorus pesticides such as cypermethrin provided a major warning for people to pay attention to environmental protection and seek safer control methods. At that time, the research on synthetic insecticides was progressing very rapidly, and Permethrin was discovered along with the deepening of insecticide research. It is a member of insecticides and has strong insect resistance. It can effectively kill pests in many different stages such as static, dynamic and larvae, and it is friendly to humans, non-target animals, and the environment, and has a short residual time after use.
With the deepening of people's research on Permethrin, its application field is gradually expanding. In addition to insecticides, Permethrin is also an effective mosquito repellent liquid ingredient, which can be used to make mosquito killers and mosquito repellents to prevent mosquito bites from spreading diseases. Moreover, the biodegradation speed of Permethrin in the natural environment is very fast, and it is harmless to the environment when the dosage is not much.
In addition, the pharmacological properties of Permethrin have also been widely used in the detection of diseases such as Coccus pneumoniae and Enterobacteriaceae, which also has important application prospects in medicine. For example, in many developing countries, drinking water is not clean, so some cellular parasitic infections often occur. Permethrin has great potential in the treatment of such diseases.
In short, the discovery of Permethrin is of great significance to environmental protection, crop protection and human health. Although it is widely used in fields such as agriculture and medical treatment, a lot of research is still needed to explore its more application fields and its impact on the environment, animals, and humans to ensure its safety and efficacy.