Pyridine azomethines

Pyridine azomethine insecticides contain a pyridine and an azomethine group. Pymetro-zine is the only member of this class. It is a highly selective antifeeding insecticide for control of aphids and whiteflies on vegetables, potatoes, citrus, fruits, hops, and ornamentals. 

In homopterans, pymetrozine prevents insects from inserting their stylus into plant tissue. The feeding disruption appears to be related to the nervous regulation of feeding behavior that consequently results in death due to starvation (Harrewijn and Kayser, 1997). Its oral LD50 in rats is 5000 mg/kg. 

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Pymetrozine (1 developmental code CGA 215 944) is an insecticide, highly active and specific against sucking pests. It is the only commercial representative of the chemical class of the pyridine azomethines. Pymetrozine is marketed by Syngenta under the trademarks of Chess , Plenum, Fulfill , Relay , and Sterling [1-4]. 

Pymetrozine (1), a pyridine azomethine, was synthesized for the first time at the end of 1986 [3, 5]. The concept behind this discovery was primarily chemically directed with, however, a strong rational element [2j. In a first step ring transformations of 1,3,4 oxadiazolon-3-yl ketones 2 with N-nucleophiles were investigated, leading to numerous new five- and six-membered N-amino heterocydes,... 

A first patent application [5] to protect compounds of the novel chemical class of the pyridine azomethines, such as 5, was filed by Ciba-Geigy (later Novartis, now Syngenta) in 1989 and within a short time some further inventions (pyridine-3-carboxaldehyde N-oxides 6 [6], imidazoles 7 [7], 3-[(N-heterocyclyl) iminomethyl]pyridines 8 [8]) were made and patented (Table 30.1.1). In 1996 Nihon Nohyaku discovered the insecticidal activity of the corresponding amino-quinazolinones 9 and 10 [9-13] and has evaluated two compounds (NNI 0101 and NNI 9768) in official field tests in Japan. In 2006 Nihon Nohyaku has enquired a common name for NNI 0101 (proposed common name pyrifluquinzon IU PAG name 1-acetyI-1,2,3,4-tetrahydro-3-[( 3-pyridyImethyIamino] -6-[ 1,2,2,2-... 

Selective Feeding Blockers (Pymetrozine, Flonicamid) 1091 Table 30.1.1 Key inventions related to the chemical class of the pyridine azomethines. 

Table 30.1.2 Pyridine azomethines - structure-activity relationship.

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