New agrochemical, fine chemical, and pharmaceutical products
often
require the development and selection of economical and effective
chemical routes to enable commercial success. Atom economy and reaction
step minimization are key drivers for low-cost routes. In addition,
capital requirements, process operability and robustness, environmental
health and safety, supply chain, quality, and intellectual property
factors should be considered in the selection process. A holistic
evaluation of process route options by a multidiscipline team of chemists
and engineers early in the route-selection phase can result in the
selection of a better route with a more focused process development
research plan. Examples from three Dow AgroSciences projects illustrate
route selection criteria.
The development of a manufacturing process for the initial commercial production of pyroxsulam sulfonamide herbicide is described. The process encompasses seven reaction steps, and includes a new route to 4-(trifluoromethyl)pyridines, a scaleable method of lithiating a pyridine intermediate, and a sulfiliminecatalyzed formation of a sulfonamide.
An extended lipophilic system that incorporated some key elements of first-generation 2,6-dihaloaryl actives, such as 1, demonstrated desirable efficacy against chewing insects as well as sap-feeding insects. These four-ring systems, based on 2, were accessed primarily via Suzuki couplings of halothiophene derivatives with appropriately substituted boronic acids. In particular, phenylthiophene systems that incorporated haloxyether groups, such as those in 3, 4, and 5, had the broadest spectrum of activity across chewing and sap-feeding insect pests. Expansion of this structure-activity relationship to include compounds with differing substitution patterns on the thiophene-C-ring and aryl-D-rings was undertaken. The synthesis and insecticidal activity of 3-aryl-5-(thiophen-2-yl)-1-methyl-1H-[1,2,4]triazoles will be described.
This paper discusses the process advantages of using commercial grade formic acid as the solvent for chlorine gas oxidation of aryl sulfides to sulfonyl chlorides. Compared to chloroxidation in methylene chloride, the chloroxidation in formic acid gave a consistently higher yield and easy product isolation for a sulfonyl chloride intermediate which was used in the production of the sulfonamide herbicide, penoxsulam.
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