Arylhydrazones, including Ferimzone

Hydrazones prepared by the reaction of aryldiazonium salts with malononitrile (trivially named carbonyl cyanide phenylhydrazones, or CCPs) have been known as uncouplers for many years [114]. Studies on the relationship between physicochemical properties and uncoupling potency have been reported [90, 91], and these show that this relationship is very similar to those for other classes of weakly acidic protonophoric uncouplers. Thus, two of the most potent uncouplers of 

Further exploration of this area of chemistry by Ishihara resulted in the discovery that arylaminopyridines are also potent uncouplers [98]. These compounds possess moderate acaricidal activity, but are better fungicides than the diarylamines. Optimization of this class of chemistry resulted in the discovery of fluazinam (4) [151]. Not only is fluazinam one of the most potent uncouplers known [99, 126], it also shows a high level of reactivity with thiols, the chlorine atom on the highly electron-deficient phenyl ring being readily displaced [126, 

It is likely that the potent, broad-spectrum antifungal activity of fluazinam is a result of the combination of these two modes of action [153, 154]. 

Fluazinam s unique combination of properties has resulted in its worldwide commercialization by Ishihara and Syngenta under various trade names, including Shirlan and Frowncide, and it is by far the most commercially important of the fungicidal uncouplers discovered to date. 

Although fluazinam has a broad spectrum of fungicidal activity it is less potent on rusts and powdery mildews [72, 156] (in contrast to the dinitrophenols, which are generally most effective against powdery mildews) and has not been commercialized for use on cereal crops. It has, however, found wide application in other crops since its first launch in New Zealand in 1988. 

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