Imidacloprid 5-ring systems

From the lead structure 2-nitromethylene-tetrahydro-l,3-thiazine (6, nithiazine) [7, 8], resulting neonicotinoids [9] such as the open-chain compounds, e.g., nitenpyram (8), acetamiprid (9), dothianidin (12), dinotefuran (13) (Chapter 29.2.1), the five-membered ring systems, e.g., imidacloprid (7), thiacloprid (11) (Chapter 29.2.2), and the six-membered ring systems, e.g., thiamethoxam (10), AKD 1022 (14)... 

The N-cyano-acetamidine acetamiprid (2, 1995, Nippon Soda Co., Ltd.) [16, 17, 18] contains, in analogy to 1 and the five-membered ring systems imidacloprid (11) and thiacloprid (12), the CPM moiety (see Chapter 29.2.2). It was discovered by Nippon Soda as part of its nitromethylene research program during optimization studies of special 2-N-cyanoimino compounds with an imidazoline... 

Fig. 29.2.1.1. Stable conformations of open-chain neonicotinoids (1,2), the five-membered ring system imidacloprid (11) and predicted properties of their binding site (Okazawa et al., 2000) [72].

Two commercial neonicotinoids containing five-membered ring systems belong to this group, imidacloprid (1) and thiadoprid (9). 

For the synthesis of imidacloprid, three principal routes were developed. The active agent can be obtained either by modification of the basic carbon scaffold, or by building up the imidazolidine or by coupling of the two ring systems (Fig. 8.56). 

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