How does Carbofuran synthesize?

  Carbofuran is a carbamate insecticide and nematicide. Created in the United States in 1963 and promoted in 1967. The pure product is white crystal. The solubility in water is 75ppm at 25 ° C. It is stable under neutral and acidic conditions, unstable in alkaline medium, and the hydrolysis rate increases with the increase of pH value and temperature. So how does Carmelane synthesize?

resolve resolution:


1. Starting from o-nitrophenol:

Chlorination reaction: isopropene is chlorinated under a certain pressure to obtain methyl chloropropene. The chlorination reaction solution is subjected to post-treatment by pressure filtration, distillation, etc., and the purity of the product can reach 96%.

Etherification reaction: o-nitrophenol and methylchloropropene are obtained in the presence of sodium carbonate to obtain 2-methallyl-o-nitrophenol ether.

The Claisen reaction: 2-methallyl-o-nitrophenol ether is heated and transposed by the Claisen reaction to form 2-(2-methallyl)-6-nitrophenol.

Cyclic reaction: The Claisen rearrangement product is ring-formed to synthesize 2,3-dihydro-2,2-dimethyl-7-nitrobenzofuran (commonly known as 7-nitro) in the presence of anhydrous magnesium chloride.



Hydrogenation: 2,3-dihydro-2,2-dimethyl-7-aminobenzofuran (commonly known as 7-amino) is obtained by pressure reduction of 7-nitro group in the presence of a palladium/carbon catalyst.


Diazotization reaction: 7-amino acid is diazotized with sodium nitrite aqueous solution and concentrated sulfuric acid to obtain 2,3-dihydro-2,2-dimethyl-7-benzofuran diazosulfate (commonly known as 7-diazonium sulphate).


Hydrolysis: 7-diazonium sulfate is hydrolyzed to 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (commonly known as 7-hydroxy compound) under the catalysis of CuSO4.


Synthesis of carbofuran: Carbofuran was synthesized in the presence of a small amount of triethylamine by reacting a 7-hydroxy compound with methyl isocyanate in a solvent.


2. MCC can also be added dropwise to the 7-hydroxy compound at 55 ° C using a methylcarbamoyl chloride method in a yield of 97%.


Starting from catechol: This process is based on catechol in anhydrous acetone solvent, in the presence of K2CO3·KI, with methyl chloropropene to form 2-methylallyloxyphenol, and then heated Position, cyclization gives a 7-hydroxy compound. The carbofuran was then synthesized by isocyanate in the presence of triethylamine.


The operation process is as follows:


Preparation of 2-methallyl oxidized phenol Under nitrogen protection, 40 parts by mass of potassium carbonate and 481 parts by mass of potassium iodide were slowly added to 312 parts by mass of catechol and 300 parts which were stirred and mixed. (mass) in anhydrous acetone solution. The obtained material was heated to reflux temperature, and 262 parts by mass of methylchloropropene was slowly added. The mixture was refluxed for 30 h, cooled and allowed to stand for 18 h, filtered, and the filtrate was concentrated under reduced pressure. The residue was purified with chloroform, washed with water, dried, concentrated, and evaporated. - methallyl oxyphenol.


7-Hydroxy compound preparation: 131 parts by mass of 2-methallyl oxyphenol is transposed and cyclized, and an exothermic reaction occurs at 200 ° C, so that the temperature is rapidly reached and maintained at 275 ° C to obtain a thick syrup. Distillation under reduced pressure gave colorless 2,2-dimethyl-2,3-dihydro-7-hydroxybenzofuran (7-hydroxy compound).


Synthesis of carbofuran: 16.6 parts by mass of 7-hydroxy compound in 14 parts by mass of diethyl ether with 5.8 parts by mass of isocyanic acid and 0.1 part by mass of triethylamine, the mixture is at room temperature Stir and precipitate a white crystalline product. The solid crystals were separated to give 17.5 parts of carbofur.