Synthesis and Structure-Activity/Selectivity Studies of Novel Heteroaryloxy, Aryloxy, and Aryl Pyridazines as Bleaching Herbicides

Insertion of Small Flexible Linkers as a Useful Scaffold Hopping Tool in Agrochemistry

“…Inserting an ethylene spacer in between the ether and carboxylic acid functions of the synthetic auxin 2,4-D (28, part of agent orange) delivers the herbicide 2,4-DB (29). 26−28 Also, the picolinic acid derivative picloram (30), another auxin-mimicking herbicide, can be elongated by a twoatom spacer to deliver fluoroxypyr (31). 27−29 Incorporation of an oxygen linker into the scaffold of the phytoene desaturase inhibiting bleaching herbicide 32 produces the pyridazinyloxypyridine derivative 33, which possesses increased herbicidal activity and corn selectivity (Scheme 6).…”

“…27−29 Incorporation of an oxygen linker into the scaffold of the phytoene desaturase inhibiting bleaching herbicide 32 produces the pyridazinyloxypyridine derivative 33, which possesses increased herbicidal activity and corn selectivity (Scheme 6). 30 In addition to the discussed complex III (section 3) and complex II (section 4) inhibitors and melanin biosynthesis inhibitors (section 5), other successful examples of chain elongation within the fungicide space exist. Prothioconazole (35), a recently introduced C 14 demethylase inhibitor, is very similar to the older cyproconazole (34) but extended by one methylene group between the phenyl ring and quarternary carbon atom.…”