Carboxylic Acid Amide (CAA) Fungicides

Isosteric Ring Exchange as a Useful Scaffold Hopping Tool in Agrochemistry

“…Therefore, not by surprise, the replacement of the 4-trifluoromethylphenyl moiety of herbicidal lead compound 9 by a similar substituted pyridyl group did not lead to a considerable enhancement of the herbicidal activity but significantly improved the ability of the resulting fluazifop-butyl ( 10 ) to translocate into the plant tissue of the target grass weeds because of an optimum partition coefficient. , Metsulfuron-methyl ( 1 ) from the first generation of sulfonylurea herbicides is only active against broadleaf weeds, and the exchange of its phenyl ring by pyridine led to nicosulfuron ( 11 ), which is a corn-selective herbicide controlling a whole range of mono- and dicotyledonous weeds. , The replacement of one of the two phenyl rings of experimental insecticide 12 by pyridine, alongside three other small modifications to the molecule, resulted in a 40-fold potency increase against lepidopteran pests and delivered chlorantraniliprole ( 13 ), a ryanodine-receptor-activating insecticide. , Also, in cellulose-synthase-inhibiting fungicide dimethomorph ( 14 ), one of the two phenyl groups has been successfully exchanged with a pyridyl ring, leading to the new commercial product pyrimorph ( 15 ) (Scheme ). , …”

“…27,28 Also, in cellulose-synthase-inhibiting fungicide dimethomorph (14), one of the two phenyl groups has been successfully exchanged with a pyridyl ring, leading to the new commercial product pyrimorph (15) (Scheme 2). 29,30 Further successful phenyl → pyridyl exchanges have been reported in the field of triazolopyrimidine herbicides (metosulam → pyroxsulam), 31,32 imidazolinone herbicides (e.g., imazamethabenz-methyl → imazapic), 33,34 synthetic auxin herbicides (2,4-D → triclopyr), 35,36 strobilurin fungicides (kresoxim-methyl → picoxystrobin), 37,38 and powdery mildew fungicides (metrafenone → pyriofenone). 39,40 The increase of the number of ring nitrogen atoms in the cyclic phenyl replacement offers even more the enhancement of water solubility, a key criterion for the systemic behavior of an active ingredient.…”

“…This ring exchange from compound 20 to compound 21 was one of the key steps in the invention pathway of oxathiapiprolin (Scheme 3). 44,45 Further successful phenyl → heterocyclyl exchanges have been reported for phenyl → benzothiazole (iprovalicarb → benthiavalicarb), 29 phenyl → dihydrobenzofuran (methoxyfenozide → fufenozide), 46 phenyl → imidazopyridine (chlorsulfuron → imazosulfuron), 25 and phenyl → thiane (tralkoxydim → cycloxydim). 47…”

Sulfur‐based functional groups in agrochemistry

“…The sulfone function occurs quite often in crop protection agents, because it is the fully oxidized version of its corresponding sulfides and sulfoxides and therefore stable against further oxidation. Examples of sulfone-containing agrochemicals are the very-long-chain fatty acid biosynthesis-inhibiting herbicide pyroxasulfone (23), [28][29][30] the experimental cellulose synthaseinhibiting fungicide XR-539 (24) 31,32 and the novel broadspectrum insecticide oxazosulfyl (25) (Fig. 4).…”

Reversal of Functional Groups as a Useful Scaffold Hopping Tool in Agrochemistry

“…Further successful examples of amide reversal have been reported in the classes of scytalone dehydratase, cellulose synthase, , oxysterol binding protein , and histone deacetylase , inhibiting fungicides, as well as for Complex I inhibiting and GABA-gated chloride channel modulating insecticides …”