Synthesis of the 15N-labelled insecticide imidacloprid

A five-step synthesis of the neonicotinoid insecticide imidacloprid (1) labelled with N-15 is reported in an overall yield of 10%. The stable isotope N-15 was introduced in the pyridine part by reaction of (NH3)-N-15 with coumalic acid methyl ester (2) to N-15-hydroxy nicotinic acid (3) followed by further reactions to N-15-2-chloro-5-(chloromethyl) pyridine (6) which was coupled with N-nitroimidazolidin-2-imine to yield 1. Copyright (c) 2006 John Wiley & Sons, Ltd.