| Molecular Formula | C14H18N6O7S |
| Physical and Chemical Properties | Chemical properties White crystals. M. p.181 ~ 182 ℃, relative density 1.44 (20 ℃), vapor pressure 0.0147 × 10-3Pa (20 ℃). The solubility in organic solvent at 20 ℃ is: acetone 31.7g/L, chloroform 234g/L, methanol 0.7g/L, hexane 0.2g/L, benzene 1.7%, ethyl acetate 3.5%; The solubility in water is 14.5mg/L. Stable to light, can be stored for half a year at 50 ℃. |
| Use | Uses of ultra-high efficiency and low toxicity of paddy field herbicides, for the control of grass weeds |
use
Sulfonylurea herbicides are characterized by ultra-high efficiency, extremely low dosage, wide herbicidal spectrum, moderate duration in soil, and safe for rice. Through root absorption, the biosynthesis of amino acids in plants is inhibited, resulting in inhibition of bud growth and stagnation of root development, and then the plant dies. Mainly used in rice fields, effective for most weeds, dosage 14~30g/hm2. The effect of pre-seedling and post-seedling treatment is very high. Apply pesticide 3~20 days after transplanting, 60kg of 0.07% granules per hectare, and spread it completely. Or 10% 210~420g of wettable powder and add 100~250kg of water to spray. Water direct seeding was applied at the 1~3 leaf stage of rice, and the dosage was the same as that in the transplanting field. Dry direct seeding was applied at the 1~3 leaf stage of rice, 250~500g of 10% wettable. In order to ensure the control effect, a certain water layer should be maintained for at least 3 days after application, while dry direct seeding rice fields should be flooded twice 1~2 days after application.
production method
Preparation of methyl -5-sulfonamido-pyrazol-4-carboxylate (pyrazolamide) is synthesized by diazonium salt: the amount of hydrochloric acid used as the chlorine atom in the chlorosulfonyl group must be controlled at about 1.05mol as much as possible, and replaced with 50% sulfuric acid can inhibit the formation of side reaction (3), thereby improving the yield. Too low sulfuric acid concentration will increase the 5-position unsubstituted pyrazole compound (4). In the decomposition reaction, acetic acid is the most suitable decomposition solvent for sulfur dioxide. In this way, the yield of (2) can be increased by 80%. (2) It can be easily converted into sulfonamide or used for the synthesis of pyrazuron. Synthesis from diazonium salt: the above method controls the appropriate conditions to obtain the main product 5-chloropyridine derivative (3), and then prepare
Synthesis from 5-tert-butyl thiopyrazole chloride: In the following reactions, R = methyl, tert-butyl, benzyl, the yield of the introduction of tert-butyl reaction is lower than that of methyl, but the yield of the latter step is much higher than that of methyl.
Thermal translocation synthesis from 5-O-pyrazolyl dimethyl thiocarbamate: 5-O-pyrazolyl dimethyl thiocarbamate was synthesized from 5-hydroxypyrazole (8) (9), and then heated at 190~200 ℃ for 30min, it can be quantitatively converted to (10). This compound can be directly derived into 5-sulfonyl chloride (2) by near chlorination, and (6) by amination.
5-hydroxypyrazole (8) can be produced by the combination of ethyl 3-ethoxy-2-ethoxycarbonylacrylate and methylhydrazine in ethanol.
The preparation of 2-amino -4, 6-dimethoxypyrimidine is detailed in the synthesis method of bensulfuron-methyl.
Synthesis of Pyrazosulfuron
The traditional method is 1-methyl -5-left amino pyridine-4-carboxylic acid ethyl ester is converted into the corresponding isocyanate, and then reacts with 2-amino -4, 6-dimethylpyrimidine.
For the preparation method of using bis (trichloromethyl) carbonate instead of phosgene to react with pyrazolamide, and then synthesize pyrazosulfuron, see the literature [5].
New method 1-methyl-5-sulfonylaminopyridine-4-carboxylic acid ethyl ester is synthesized by the corresponding sulfonyl carbamate of the intermediate, and CH3OH is removed in time through the reaction system to make the reaction proceed smoothly. This method does not use phosgene, and the yield is also high.