- 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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supporting information
p. 1032 - 1036
(2019/03/17)
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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 preparing esters of 3,5,6-trichlorosalicyclic acid
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An improved process for the synthesis of esters of 3,5,6-trichlorosalicylic acid in quantitative yield comprises reacting the acid with an alcohol under distillation conditions in the presence of a titanium ester or chelate catalyst, whereby byproduct ether formation from the alcohol is suppressed. The process is especially applicable to a process by which salicylic acid is chlorinated first in concentrated sulfuric acid and then with iodine catalyst to make the trichlorosalicylic acid which is extracted and then reacted with an alcohol and a titanium catalyst to make the ester.
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- Synthesis and Evaluation of Diaryl Oxalate Esters for Low-Intensity Chemiluminescent Illumination
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Various diaryl oxalate esters have been prepared from oxalyl chloride and substituted salicylates.A number of intermediates and byproducts were obtained from chlorinations of salicylic acid and their mechanistic significance has been discussed.The chemiluminescent emission from the oxalates in the presence of hydrogen peroxide has been examined in the search for low-intensity illumination of at least 10 h duration.Bis(2-alkoxycarbonyl-4,6-dinitrophenyl) oxalates were too unstable while the chemiluminescence of the bis(6-alkoxycarbonyl-2,4,5-trichlorophenyl) oxalates c ould not be adjusted suitably.Some bis(6-alkoxycarbonyl-2,4-dichlorophenyl) oxalates were prepared and, by treatment with various combinations of potassium salicylate and oxalic acid, satisfactory low-intensity light emission could be achieved.
- Dowd, Christopher D.,Paul, D. Brenton
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- Processes for preparing 3,5,6-trichlorosalicylic acid and esters thereof
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An improved single-pot process for synthesis of 3,5,6-trichlorosalicylic acid and esters thereof is described. Salicylic acid is chlorinated first in concentrated sulfuric acid and then with iodine catalyst to make the trichlorosalicylic acid which is extracted and then reacted with an alcohol to make the ester.
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