- Hybrid catalytic effects of K2CO3 on the synthesis of salicylic acid from carboxylation of phenol with CO2
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As a base-promoted Kolbe-Schmitt carboxylation reaction, the mechanism of synthesis of salicylic acid derivatives from phenols with CO2 in the industry is still unclear, even up to now. In this paper, synthesis of 3,6-dichloro salicylic acid (3,6-DCSA) from 2,5-dichloro phenoxide and CO2 was investigated in the presence of K2CO3. We show the reaction can proceed by itself, but it goes at a slower rate as well as a lower yield, compared to the case with the addition of K2CO3. However, the yield of 3,6-DCSA is only minorly affected by the size of K2CO3, which cannot be explained from the view of catalytic effect. Therefore, K2CO3 may on one hand act as a catalyst for the activation of CO2 so that the reaction can be accelerated, while on the other hand, it also acts as a co-reactant in deprotonating the phenol formed by the side reaction to phenoxide, which is further converted to salicylate.
- Gu, Miaofei,Yan, Xingxing,Cheng, Zhenmin
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- O-demethylations catalyzed by rieske nonheme iron monooxygenases involve the difficult oxidation of a saturated C-H bond
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Dicamba monooxygenase (DMO) catalyzes the O-demethylation of dicamba (3,6-dichloro-2-methoxybenzoate) to produce 3,6-dichlorosalicylate and formaldehyde. Recent crystallographic studies suggest that DMO catalyzes the challenging oxidation of a saturated C-H bond within the methyl group of dicamba to form a hemiacetal intermediate. Testing of this hypothesis was made possible by our development of two new independent techniques. As a novel method to allow use of 18O2 to follow reaction products, bisulfite was used to trap newly formed 18O-formaldehyde in the stable adduct, hydroxymethanesulfonate (HMS-), and thereby prevent the rapid exchange of 18O in formaldehyde with 16O in water. The second technique utilized unique properties of Pseudomonas putida formaldehyde dehydrogenase that allow rapid conversion of 18O-formaldehyde into stable and easily detectable 18O-formic acid. Experiments using these two new techniques provided compelling evidence for DMO-catalyzed oxidation of the methyl group of dicamba, thus validating a mechanism for DMO [and for vanillate monooxygenase, a related Rieske nonheme iron monooxygenase] that involves the difficult oxidation of a saturated C-H bond.
- Jiang, Wenzhi,Wilson, Mark A.,Weeks, Donald P.
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- Synthesis method of 3,6-dichlorosalicylic acid
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The invention provides a synthesis method of 3,6-dichlorosalicylic acid. The synthesis method comprises the following steps: S1, brominating o-cresol to obtain 2-methyl-4-bromophenol; S2, chlorinating2-methyl-4-bromophenol to obtain 2-methyl-3,6-dichloro-4-bromophenol; S3, oxidizing 2-methyl-3,6-dichloro-4-bromophenol to obtain 3,6-dichloro-4-bromosalicylic acid; S4, debrominating 3,6-dichloro-4-bromosalicylic acid to obtain 3,6-dichlorosalicylic acid. In the synthesis route, the raw materials are easily available and the comprehensive cost is low. The preparation process comprises directional bromination and directional chlorination, selectivity is high, product quality is stable, and total yield is high. Besides, the preparation process of 3,6-dichlorosalicylic acid is simple, and industrial implementation is facilitated.
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- A new process to prepare 3,6-dichloro-2-hydroxybenzoic acid, the penultimate intermediate in the synthesis of herbicide dicamba
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Glyphosate [N-(phosphonomethyl)glycine] is a broad spectrum, post-emergent herbicide that is among the most widely used agrochemicals globally. Over the past 30 years, there has been a development of glyphosate-resistant weeds, which pose a significant challenge to growers and crop scientists, resulting in lower crop yields and increased costs. 3,6-Dichloro-2-methoxybenzoic acid (dicamba) is the active ingredient in XtendiMax a standalone herbicide developed by Bayer Crop Science to control broadleaf weeds, including glyphosate-resistant species. 3,6-Dichloro-2-hydroxybenzoic acid (3,6-DCSA) is the penultimate intermediate in the synthesis of dicamba. Existing dicamba manufacturing routes utilize a high temperature, high pressure Kolbe-Schmitt carboxylation to prepare 3,6-DCSA. Described in this Letter is a new, non-Kolbe-Schmitt process to prepare 3,6-DCSA from salicylic acid in four chemical steps.
- Walker, Daniel P.,Harris, G. Davis,Carroll, Jeffery N.,Boehm, Terri L.,McReynolds, Matthew D.,Struble, Justin R.,van Herpt, Jochem,van Zwieten, Don,Koeller, Kevin J.,Bore, Mangesh
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p. 1032 - 1036
(2019/03/17)
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- Continuous production processes of dicamba methyl ester and dicamba methyl ester emulsifiable concentrate
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The invention provides a continuous production process of dicamba methyl ester. The process comprises the following steps: A) 5-bromo-3,6-dichlorosalicylic acid is subjected to a reaction under an alkaline condition and under the action of metal powder to remove bromine atoms in para-positions of hydroxyl, and 3,6-dichlorosalicylic acid is obtained; B) 3,6-dichlorosalycylic acid and halomethane are subjected to an etherification reaction in a mixed solvent of water and methanol, and methyl 3,6-dichloro-2-methoxybenzoate is obtained; C) methanol is removed by distillation; D) a system after distillation is left to stand for laying, an organic phase is distilled, and dicamba methyl ester is obtained. By means of the preparation process, continuous production can be realized, workers are notrequired to make direct contact with materials, the control degree is high, the production operation environment is greatly improved and safer, the process route and equipment are simple, the production cost is low, besides, the product yield and purity are greatly improved, and a superior route suitable for mass industrial production is provided.
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- Preparation method of dicamba
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The invention provides a preparation method of dicamba. The preparation method comprises the steps as follows: A) salicylic acid and bromine or hydrogen bromide are subjected to a reaction in concentrated sulfuric acid, 5-bromosalicylic acid is obtained; B) 5-bromosalicylic acid and chlorine are subjected to a chlorination reaction, 5-bromo-3,6-dichlorosalycylic acid is obtained; C) 5-bromo-3,6-dichlorosalycylic acid is subjected to a debromination reaction under the alkaline condition and under the action of metal powder, and 3,6-dichlorosalycylic acid is obtained; D) 3,6-dichlorosalycylic acid and halomethane are subjected to an etherification reaction in a mixed solvent of water and methanol, and methyl-3,6-dichloro-2-methoxybenzoate is obtained; E) methanol is removed by distillation;F) a system after distillation is left to stand for laying, an organic phase is distilled, and dicamba methyl ester is obtained; G) dicamba methyl ester is subjected to alkaline hydrolysis, acidification and drying, and dicamba is obtained. The route comprises few steps and has low difficulty, the equipment requirement and investment are lower, continuous production can be realized, no three wastes are produced, and the product yield and purity are higher.
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- Preparation method of micamba methyl ester
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The invention provides a preparation method of micamba methyl ester. The preparation method comprises the steps as follows: A) salicylic acid and bromine are subjected to a reaction in concentrated sulfuric acid, 5-bromosalicylic acid is obtained; B) 5-bromosalicylic acid and chlorine are subjected to a chlorination reaction, 5-bromo-3,6-dichlorosalycylic acid is obtained; C) 5-bromo-3,6-dichlorosalycylic acid is subjected to a debromination reaction under the alkaline condition and under the action of metal powder, and 3,6-dichlorosalycylate is obtained; D) 3,6-dichlorosalycylate and halomethane are subjected to a methylation reaction in methanol and a quaternary ammonium salt phase transfer catalyst, and 3,6-dichloro-2-methyl methoxybenzoate is obtained; E) methanol is removed by distillation; F) a system after distillation is left to stand for laying, an organic phase is distilled, and dicamba methyl ester is obtained. By means of the preparation method, the yield and purity are higher, the route is simple and the production cost is low.
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- Total recycling method of salicylic acid in preparation process of 3,6-dichlorosalicylic acid
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The invention provides a total recycling method of salicylic acid in a preparation process of 3,6-dichlorosalicylic acid. The method comprises steps as follows: A), salicylic acid is subjected to reaction with bromine or hydrogen bromide in concentrated sulfuric acid, 5-bromosalicylic acid is obtained; B), 5-bromosalicylic acid is subjected to chlorination with chlorine, and 5-bromo-3,6-dichlorosalicylic acid is obtained; C), 5-bromo-3,6-dichlorosalicylic acid is subjected to debromination reaction under the action of a catalyst, and crude 3,6-dichlorosalicylic acid is obtained; D), crude 3,6-dichlorosalicylic acid is recrystallized in xylene or toluene, and pure 3,6-dichlorosalicylic acid and an impurity-containing solvent are obtained, wherein impurities comprise 3-chlorosalicylic acid,3,5-dichlorosalicylic acid and 3-bromo-6-chlorosalicylic acid; E), the impurity-containing solvent is subjected to alkali washing, a water phase is obtained by liquid separation, a catalyst is added to the water phase for hydrogenation dehalogenation reaction, filtering is performed to remove the catalyst, the filtrate is acidified, and salicylic acid is obtained and recycled to step A). Total recycling of salicylic acid is realized, and the environmental benefit is high.
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- Preparation method of 3,6-dichlorosalicylic acid
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The invention provides a preparation method of 3,6-dichlorosalicylic acid. The method comprises the following steps: 5-bromo-3,6-dichlorosalicylic acid is subjected to debromination reaction in the alkaline condition and under action of metal powder, and 3,6-dichlorosalicylic acid is obtained. 5-bromo-3,6-dichlorosalicylic acid is subjected to selective debromination reaction in the alkaline condition and under action of metal powder, the reaction has high selectivity, the conversion rate is high, the reaction rate is high, and the prepared product has high purity. The process route is simple,equipment is conventional, the metal powder is easy to recycle, and the cost is low.
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- Selective removing method of benzene ring hydroxyl para-bromine and preparation method of dicamba
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The invention provides a selective removing method of benzene ring hydroxyl para-bromine. The method comprises following steps: a compound represented as formula (I) in the description is subjected toa reaction under the alkaline condition and the action of metal powder to remove hydroxyl para-bromine ions, and a compound represented as formula (II) in the description is obtained. The benzene ring hydroxyl para-bromine ions are selectively removed under the alkaline condition and the action of the metal powder, the reaction has higher selectivity, conversion rate and reaction rate are high, and a prepared product has higher purity.
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Page/Page column 5-8
(2019/06/05)
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- Synthesis method of 2-hydroxyl-3,6-dichlorobenzoic acid
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The invention discloses a synthesis method of 2-hydroxyl-3,6-dichlorobenzoic acid. The synthesis method of the 2-hydroxyl-3,6-dichlorobenzoic acid comprises the following step: under existence of protective gas, carrying out nucleophilic substitution reaction in methanol to obtain a compound 1. The method has the advantages that the raw materials are readily available, the amount of wastewater produced in a reaction process is relatively small, the process is simple, and the purity of a product is high.
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- Dicamba preparation process
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The invention belongs to the technical field of herbicide dicamba preparation and relates to a dicamba preparation process. The dicamba preparation process includes steps: taking benzene as a raw material to generate 1,2,4-trichlorobenzene through directional chlorination, catalysis, re-chlorination and rectification; hydrolyzing the 1,2,4-trichlorobenzene to generate a mixture of 2,5-dichlorophenol and 2,4-dichlorophenol, and separating and purifying to obtain 2,5-dichlorophenol; using the 2,5-dichlorophenol to prepare 3,6-dichlorosalicylic acid; subjecting the 3,6-dichlorosalicylic acid to methylation, saponification, acidification and the like to obtain dicamba. By optimization of technical steps and parameters, the whole dicamba preparation process has advantages of simplicity, low cost, high yield, high selectivity, remarkable reduction of wastewater and increase of equipment utilization rate.
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- An improved 3,6-di- chlorine salicylic acid method for the preparation of (by machine translation)
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The invention discloses an improved preparation method of 3,6-dichloro salicylic acid. The improved preparation method of 3,6-dichloro salicylic acid comprises the following steps: carrying out reaction on 2,5-dichlorophenol and an alkali liquor, then adding an organic solvent, and carrying out reduced pressure dehydration; adding potassium carbonate, a dehydrating agent and a stabilizer after dehydration is finished, and carrying out reaction at the temperature of 130-140 DEG C for 30-60 minutes; adding materials into a high pressure autoclave, heating to 130-140 DEG C, then introducing CO2, and carrying out high pressure carboxylation reaction; carrying out aftertreatment after the reaction is finished, so that 3,6-dichloro salicylic acid is obtained. The improved preparation method of 3,6-dichloro salicylic acid has the advantages that oxygen is isolated before dehydration and carboxylation, so that oxidation of oxygen to a product is avoided; the dehydrating agent and the stabilizer are added before carboxylation, so that water in a system and positive hydrogen ions generated during carboxylation are further removed, stability of the system is maintained, yield is guaranteed and appearance of the product is greatly improved, usage amount of potassium carbonate is reduced, and an aftertreatment process is simplified; besides, modification on equipment is less, the current production enterprises can implement improvement conveniently, and quick benefit can be obtained.
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Paragraph 0038-0040
(2017/05/06)
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- Method for preparing dicamba
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The invention relates to a method for preparing dicamba and belongs to the technical field of herbicide dicamba. The method comprises that benzene as a raw material is subjected to directional chlorination and catalysis, the product is purified to form 1, 4-dichlorobenzene, the 1, 4-dichlorobenzene is halogenated and hydrolyzed in the presence of a catalyst to form 2, 5-dichlorophenol, 3, 6-dichlorosalicylic acid is prepared from 2, 5-dichlorophenol and the 3, 6-dichlorosalicylic acid undergoes methylation, saponification and acidification reactions to produce dicamba. Through process and parameter optimization, the method has simple processes, realizes a low cost, a high yield and high selectivity, observably reduces a waste water amount and improves a device use rate.
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Paragraph 0095-0121
(2018/02/04)
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- 3,6-DICHLOROSALICYLIC ACID COMPOUNDS AND RELATED SYNTHETIC PROCESSES
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The present disclosure relates, in general, to 5-halo-3,6-dichlorosalicylic acid compounds, 5-halo-3,6-dichlorosalicyaldehyde compounds, processes for preparing 5-halo-3,6-dichlorosalicylic acid compounds, processes for preparing 5-halo-3,6- dichlorosalicyaldehyde compounds, processes for preparing 3,6-dichlorosalicylic acid compounds, and processes that employ such compounds as intermediates in the preparation of the herbicide dicamba.
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- Process for the preparation of 3,6-dichloro-salicyclic
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An improved process for the preparation of 3,6-dichlorosalicylic acid by carboxylation of potassium 2,5-dichlorophenolate with carbon dioxide in xylene at elevated pressure, where the improvement consists of adding finely powdered, anhydrous potassium carbonate to the reaction mixture, whereby the yield of 3,6-dichloro-salicylic acid is significantly increased.
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- Process for the production of 2-methoxy-3,6-dichlorobenzoic acid
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This invention discloses a process for the production of 2-methoxy-3,6-dichlorobenzoic acid which comprises reacting 2-amino-3,6-dichlorobenzoic acid with nitrous acid to form the corresponding diazonium salt, hydrolyzing the diazonium salt to form 2-hydroxy-3,6-dichlorobenzoic acid and methylating said hydroxy acid.
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