1 fluorine-containing herbicide varieties
1. 1 sulfoxide and fluoxetine.
Sulfoxide and ketoprofen belong to sulfadiazine herbicides containing difluoromethylsulfonamide groups (see figure 1).
Bensulfuron-methyl is a new herbicide for pre-emergence and post-emergence in rice fields discovered and developed by Japan Combinatorial Chemical Company. The dosage is 50 ~ 75 kg/ha. The compound has a broad-spectrum weeding effect on annual gramineous weeds, sedges, broadleaf weeds and sulfonylurea-resistant weeds, does not cause phytotoxicity to rice, and is safe to aquatic organisms such as fish and fleas and the environment. Takumi et al. summarized different synthetic routes of N- (pyrimidine -2- carbonylphenyl) sulfonamide and its derivatives, and studied the structure-activity relationship of substituents on sulfonyl groups. The results showed that sulfonamides containing CF2H substituents had strong herbicidal activity and broad spectrum. The synthetic method of sulfluramid is shown in Figure 2. 3- (methoxymethyl) -2- nitroacetonitrile was used as raw material to react with 4,6-dimethoxy -2- methylsulfonyl pyrimidine, and the obtained intermediate was finally obtained through oxidation, two-step reduction and substitution.
Fluorone sulfanilamide is a new herbicide discovered and developed by Bayer Company, and its dosage is 20 ~ 50 ga.i./hm2. The main target weeds are gramineous weeds, sedge and broadleaf weeds, and there is no potential accumulation in organisms. The mechanism of action of flufenuron and flufenapyr is similar, and both of them inhibit acetolactate synthase.
The synthetic method of fluorosulfonamide is shown in Figure 3. The corresponding 7-F- indole-2- one was synthesized from 2-fluoroaniline and methyl methylthioacetate by Gassman reaction. After reduction to eliminate methylthio group, it reacted with 2- chloro-4,6-dimethoxytriazine to obtain 3-(4,6-dimethoxy-1, 3,5-triazine) -7- fluoroindole -2- one. Because difluoromethylsulfonyl chloride is very unstable under alkaline conditions, difluoromethylsulfonation of indolone was realized with N- methylimidazole as base. Indole ketone was oxidized by FeSO _ 4/H _ 2O _ 2 to further generate corresponding ketone, and finally methylated to generate fluorosulfonamide.
Difluoromethanesulfonyl chloride is used for the synthesis of fomesafen and flufenapyr. Difluoromethanesulfonyl chloride is synthesized from Freon and benzyl mercaptan in two steps (see Figure 4), which is a commercial and easily available intermediate.
1.2 triazinyl fluoroamine and nonazinyl fluoroamine
Triazine fluroxypyr (see Figure 5) is a new triazine herbicide developed by Japanese company Idemitsu Kosan. It is mainly used to control gramineous weeds and broadleaf weeds before and after seedling in rice fields, and the dosage is 100~200ga.i./hm2. It was put on the market in 2006. Trioxaprop can inhibit the photosynthesis, microtubule formation and cellulose formation of weeds, and has a brand-new weeding mechanism, which is conducive to delaying the formation of weed resistance. The synthesis method is shown in Figure 6. 2- fluoroethyl isobutyrate, an important raw material of this synthetic route, is prepared by the reaction of 2- hydroxyethyl isobutyrate and hydrogen fluoride, but this situation is easily eliminated by this fluorination reaction, so the yield is low.
20 1 1, Bayer introduced a new active ingredient, namely indazine flufenamide, which is an efficient cellulose biosynthesis inhibitor (CBI). It is a pre-seedling and post-seedling herbicide, which can be used to control weeds in fixed crops such as citrus, grapes, fruit trees and nut trees. Such as industrial plantations, perennial sugar cane, lawns, golf courses, lawn farms, leisure lawns, ornamental areas, non-crop areas, Christmas tree farms and woodlands. The application amount and spectrum of indoxacarb in weed control have made a great breakthrough, but the compound contains three chiral centers, which makes the synthesis of indoxacarb a chemical problem.
The intermediate (1R, 2s)-2,6-dimethyl-2,3-dihydro-1H- indene-1- amine was synthesized with 2,6-dimethyl-2,3-dihydro-/kloc-.
The synthesis of chiral 2-F- propionic acid or its ester starts from natural lactate and is obtained by OH/F enantioselective substitution. 1 method reported in 1993 is to fluorinate methanesulfonate with KF in N, N- dimethylformamide. Because methyl acrylate is produced in the reaction process, which requires complicated purification, the yield is low (see Figure 8).
Later, Cost-efficient developed several cost-effective routes and obtained several tons of 2-F- propionate. One of the most effective methods is to activate OH groups with SO2F2 or SOCl2, and then react with HF, which has excellent atomic economy (see Figure 9).
In 2007, Bayer also applied for the patent of fluoroalkylamine reagent. TFEDMA is used for one-step deoxidation and fluorination of lactic acid enantiomers with a yield of 75%-80% and very high enantioselectivity, as shown in Figure 10.
The synthetic route of indazine fleroxacin is shown in figure 1 1. Aluminum isopropoxide was added to the reaction mixture as Lewis acid, which promoted the formation of biguanide under relatively mild reaction conditions, and finally indazine fluorozinone was obtained with high yield and good purity.
1.3 fluclopyridinic acid and fluclopyridinic acid
Fluchloropyridine ester and fluchloropyridine ester are aryl pyridine ester compounds developed by Dow Agron Company (see figure 12), belonging to phytohormone herbicides. By combining with receptor hormones in plants, it stimulates excessive cell division and blocks conductive tissues, leading to nutrient depletion and death of plants. Fluchloropyridine ester is mainly suitable for grain fields, including barley, wheat, barley rye and so on. It can control a variety of broad-leaved weeds and post-seedling malignant weeds with the dosage of 10~20ga.i./hm2, which is safe for mammals, low in acute and chronic toxicity and high in rice. Chloropyridine ester is mainly suitable for paddy fields, which can effectively control broad-leaved weeds such as Euphorbia spurge and barnyard grass. It is a pre-and post-emergence herbicide with the dosage of 33.3~66.7ga.i./hm2, which is environmentally friendly and safe for other organisms.
There are two main routes for the synthesis of fluclopyridine ester. The first route was obtained from 4- chloro -2- fluoro-bromobenzene by hydroxylation, methylation, boronization and Suzuki coupling (see figure 13).
Route 2 takes 2- pyridinecarboxylic acid or 2- fluoro -4- chloro -3- methoxybenzaldehyde as raw materials, prepares zinc reagent, closes the ring, and constructs pyridine ring to obtain fluclopyridine ester (see figure 14).
The synthesis of fluoropyridyl ester is similar to that of fluoropyridyl ester. The target product was obtained from 4- chloro -2- fluorobromobenzene by hydroxylation, methylation, borate, Suzuki coupling, hydrolysis and esterification (see figure 15).
1.4 trifluozine
20 14 BASF herbicide trifluoling was approved by ISO. Ma Song trifluoride is a herbicide with protoporphyrin oxidase (PPO) inhibitor. By interfering with chlorophyll biosynthesis, weeds died before and after emergence, and the dosage was 100ga.i./hm2. This product is mainly used in cereals, corn, soybeans, peanuts, oranges, pears and other crops, and also used to control gramineous weeds and broad-leaved weeds such as Chenopodium album, ragweed, wild radish, ryegrass, catnip, and some important resistant weeds such as amaranth and ragweed. The herbicide has low toxicity and high biological safety.
There are three main synthetic routes of trifluralin. The first route (see figure 16) is obtained by nucleophilic substitution, benzene ring nitration, nitro reduction, nitrogen atom acylation, nitrogen atom alkylation and ring closure of m-fluorophenol and bromodifluoroacetyldimethylamine.
Route 2 (see figure 17) takes 5- fluoro -2- nitrophenol as the starting material, and the target product is obtained through eight steps of reduction, amidation, etherification, nitration, substitution, reduction, preparation of cyanate ester and cyclization.
The third synthetic route (see figure 18) is to optimize the last step of the triazine ring synthesis reaction based on the first route, and prepare the target by one-step cyclization with 6- amino -2,2,7-trifluoro -4- propyl -2- alkynyl -4H- benzoxazine -3- one as the intermediate.