Description
Cloransulam-methyl is a post-emergence herbicide. It has a moderate aqueous solubility, is non-volatile and, based on its chemical properties, is mobile and may leach to groundwater in some situations. It is generally non- persistent in soil systems but usually degrades quickly in aquatic systems via photolysis. It is not susceptible to hydrolysis. It has a low mammalian toxicity and has a high potential for bioaccumulation. It is a skin and eye irritant. It has a low level of toxicity to birds and aquatic invertebrates but is more toxic to fish, aquatic plants, algae, earthworms and honeybees.
Uses
Cloransulam-methyl is a triazolopyrimidine sulfonanilide herbicide. Cloransulam-methyl can be used to control broadleaf weeds in soybean by acetolactate synthase (ALS) inhibition[1].
Definition
ChEBI: The methyl ester of cloransulam. An inhibitor of acetohydroxyacid synthase (AHAS), it prevents the synthesis of amino acids in plants and is used as a herbicide for the control of post-emergence control of broad-leaved weeds in soybeans. It is not approved
for use within the European Area.
Production Methods
Cloransulam-methyl is commercially produced through a multi-step organic synthesis designed for large-scale manufacturing, typically involving 5–7 reactions with high yields and minimal waste. The process begins with the construction of the 5-ethoxy-7-fluoro-[1,2,4]triazolo[1,5-c]pyrimidine core from basic heterocyclic precursors like 3-amino-1,2,4-triazole and a suitably substituted pyrimidine derivative via cyclocondensation in the presence of base and solvent (e.g., ethanol or DMF) at elevated temperatures. The 2-sulfonyl chloride intermediate is then formed by chlorosulfonation using chlorosulfonic acid or thionyl chloride. This is followed by nucleophilic coupling with methyl 2-amino-3-chlorobenzoate in a basic medium (e.g., pyridine or triethylamine in dichloromethane) to yield the final sulfonamide product.
Mechanism of action
Inhibits plant amino acid synthesis - acetohydroxyacid synthase AHAS.
Metabolic pathway
When 14C-cloransulam methyl is incubated with soils,
the degradation proceeds via the hydrolysis of the
ester group and O-de-ethylation on the
triazolopyrimidine ring to yield the three identified
metabolites, cloransulam, 5-hydroxycloransulam
methyl, and 5-hydroxycloransulam. These metabolites
are significantly less phytotoxic than the parent
herbicide.
References
[1] Jeffrey D. Wolt, et al. Products and Kinetics of Cloransulam-methyl Aerobic Soil Metabolism. J. Agric. Food Chem. 1996, 44, 1, 324-332.
