Application of cross-coupling and metalation chemistry of 3(2H)-pyridazinones to fungicide and herbicide discovery

Reaction of chloropyridazin-3(2H)-ones with iodide. Part II.

“…At a moderately high temperature (120 o C) and for a short reaction time (2h) the substitution of chlorine-by iodine atom in position 4 was predominant, the main product was 5-chloro-4-iodo-2-methyl-6-phenylpyridazin-3(2H)-one 9. It is noted that 5-chloro-4-iodopyridazinones were prepared earlier by Stevenson et al 18 and Haider et al 19 starting from 3-chloro-2-iodomalealdehydic acid. 20 At a somewhat higher temperature (140 o C) a dramatic change occurred and the 4-deiodinated 5-chloro-2-methyl-6-phenylpyridazin-3(2H)-one 1 was the main product.…”

Pyridazine Chemistry in Crop Protection

“…The tetrahydrocinnolinone derivative 36 has been designed as ring‐enlarged analog of the commercialized protoporphyrinogen‐IX‐oxidase (PPO, Protox) inhibiting herbicide azafenidin ( 35 ) . A similar type of ring enlargement has been performed during the derivatization of the p ‐hydroxyphenylpyruvate‐dioxygenase (HPPD) inhibiting pyrazole derivative DTB ( 37 ), the active principle of the market products pyrazolinate and pyrazoxyfen, to the closely related dihydropyridazinone 38 and pyridazinone 39 , which both are also herbicidally active. The [1,2,4]triazolo[1,5‐ b ]pyridazine derivative 41 has been prepared as analog of the phytoene desaturase inhibiting bleaching herbicide 40 bearing a [1,2,4]triazolo[1,5‐ a ]pyrimidine scaffold (Scheme ) .…”

“…The strobilurin 49 , in which azoxystrobin's pyrimidine center core has been replaced by a pyridazine ring, has its strength against Venturia inaequalis (apple scab) . The pyridazinone 51 mimics the triazolone pharmacophore of the former developmental compound 50 and showed broad‐spectrum activity against several important plant pathogens (Scheme ) .…”

A Regioselective One-Pot, Three Component Synthesis of 6-Aryl-4-cyano-3(2H)-pyridazinones in Water

“…[6][7][8][9][10][11][12] They have been used as herbicides, such as Norflurazon 1 and as insecticides, like Pyridaben 2 for crop protection. [13] In drug discovery, pyridazinones were identified as selective COX-2 inhibitors (ABT-963 3 [14] and CK −126 [15] ) and α 4 integrin receptor antagonists. [16] Pyridazinone derivatives are also cyclooxygenase-2 inhibitors 4, thereby acting as anti-inflammatory drugs, [17,18] and show strong affinity for α 1 -adrenergic receptors.…”