In 1985, chemists at the Dr R. Maag subsidiary of Hoffmann-La Roche filed patents to 3-aryl uracil derivatives which had herbicidal activity.[4] The work was continued by Ciba-Geigy and further patents claiming additional esters were published, including to butafenacil (CGA276854), which was marketed in 2001.[5][6]BASF scientists investigated the chemistry and patented an analog where the carboxylic ester of butafenacil was replaced by a sulfamoylcarboxamide.
It was developed under the code number BAS800H and first marketed in 2008 with the brand name Kixor.[7][1]
Synthesis
As described in the BASF patent, the key step in the preparation of saflufenacil involved the reaction between a substituted aniline and an oxazinone. 2-chloro-4-fluoro-5-aminobenzoic acid and 2-dimethylamino-4-(trifluoromethyl)-6H-1,3-oxazin-6-one were heated in acetic acid to form the ring systems of the herbicide in over 90% yield, with further standard chemical transformations to generate the final product.[7]
Mechanism of action
Saflufenacil works by inhibiting protoporphyrinogen IX oxidase (PPO), preventing chlorophyll formation, and resulting in accumulation of protoporphyrin IX which is a potent photosensitizer. This activates oxygen, causing lipid peroxidation with rapid loss of membrane integrity and function. The effects visible on whole plants are chlorosis and necrosis.[8] In corn and some varieties of soyabean the effects are insufficient to cause serious damage, leading to useful selectivity.[9][10]
The estimated annual use of saflufenacil in US agriculture is mapped by the US Geological Service and shows that in 2018, the latest date for which figures are available, approximately 600,000 pounds (270,000kg) were applied — mainly in corn and soybean.[12] The compound is also registered for use in Australia but not in the European Union.[1]
References
123Pesticide Properties Database. "Saflufenacil". University of Hertfordshire.
↑USpatent 4746352,Wenger J.&Winternitz P.,"3-(5-Carboxy-4-Substituted-Phenyl)-(thio) Uracil esters and salts",issued 1988-05-24, assigned to Hoffmann-La Roche Inc.
↑USpatent 5183492,Suchy M.; Winternitz P.& Zeller M.,"Herbicidal 3-aryluracils",issued 1993-02-02, assigned to Ciba-Geigy Ag
↑Pesticide Properties Database. "Butafenacil". University of Hertfordshire.
12USpatent 6534492,Carlsen M.; Guaciaro M. A.& Takasugi J. J.,"Uracil substituted phenyl sulfamoyl carboxamides",issued 2003-03-18, assigned to BASF SE
↑Theodoridis, George (2016). "Carboxylic-Acid-Containing Protoporphyrinogen-IX-Oxidase-Inhibiting Herbicides". Bioactive Carboxylic Compound Classes: Pharmaceuticals and Agrochemicals. pp.347–356. doi:10.1002/9783527693931.ch26. ISBN9783527339471.
↑Grossmann, Klaus; Niggeweg, Ricarda; Christiansen, Nicole; Looser, Ralf; Ehrhardt, Thomas (2010). "The Herbicide Saflufenacil (Kixor™) is a New Inhibitor of Protoporphyrinogen IX Oxidase Activity". Weed Science. 58 (1): 1–9. Bibcode:2010WeedS..58....1G. doi:10.1614/WS-D-09-00004.1. S2CID86227686.
