Stereochemistry and active conformation of a novel insecticide, acetamiprid

✍ Scribed by Nakayama, Akira; Sukekawa, Masayuki; Eguchi, Yoshiyuki

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 477 KB
• Volume: 51
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199710)51:2<157::aid-ps620>3.0.co;2-c

✦ Synopsis

Acetamiprid, (NI-25 ; (E)-N1- [(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), is a novel neonicotinoid insecticide having an Ncyanoacetamidine structure as its characteristic feature. The [1H] and [13C]-NMR spectra indicated the existence of two di †erent structures in acetamiprid at room temperature in solution. The measurement of CH-NOE and CÈC coupling constants proved the E-conÐguration at the cyanoimino group in both existing structures. The [13C] chemical shifts of and the long range CÈH coupling N-CH 3 in the formamidine analogue of acetamiprid suggested that there exist two conformers generated by the rotation of CÈC single bond in the amidine moiety. Dynamic NMR spectra of acetamiprid and the computer simulation of the twosite exchange demonstrated that the two conformers change slowly to each other at room temperature. The conformational analysis by semi-empirical molecular orbital calculations using MNDO-PM3 method predicted four conformers as energy-minimum structures, among which two E-conformers were more stable than Z-conformers. One of the E-conformers in which two methyl groups are in cis conÐguration was superimposable onto the structure of imidacloprid, which is a known neonicotinoid insecticide having more rigid structure. This E-conformer was assumed as the active conformation of acetamiprid on the basis of the molecular similarity in terms of steric and electrostatic properties.