An overview of radio or stable isotope-labeled cis-neonicotinoid analogs

To support the metabolism and toxicology study of cis-neonicotinoids, radio or stable isotope was introduced into different sites of the key intermediate 2-chloro-5-((2-(nitromethylene)imidazolidin-1-yl)methyl)pyridine (6-Cl-PMNI). [3H2]- and [14C]-label were successively prepared from initial materials NaB3H4 and [14C]-nitromethane, respectively. Similarly, [D2]-6-Cl-PMNI was prepared from NaBD4 in four steps, with 52.6% overall isotopic yield, and dual-labeled [D2, 13C]-target was obtained from NaBD4 and [13C]-nitromethane, affording overall isotopic yield of 42.5%. Moreover, [14C2] was introduced from [U-14C]-ethylenediamine dihydrochloride in three steps, with a 58.3% overall chemical yield. Finally, typical labeled cis-neonicotinoids paichongding and cycloxaprid were prepared and characterized. The methods were proved to have good generality in the synthesis of other cis-neonicotinoids, and all results would be useful in metabolism studies of new cis-neonicotinoids. Copyright (c) 2012 John Wiley & Sons, Ltd.