The 14C, 13C and 15N syntheses of MON 37500, a sulfonylurea wheat herbicide

[14C] and [13C]MON 37500 labeled in the imidazopyridine (Im) ring system were synthesized in seven steps in an overall yield of 39 and 28%, respectively, from [2-14C] and [2-13C]chloroacetic acid. [14C]MON 37500 labeled in the pyrimidine (Pd) ring system was synthesized from [2-14C]diethyl malonate in four steps in 48% yield. Lastly, [15N]MON 37500 was prepared in three steps in an overall yield of 28% from [15N]ammonium chloride. Copyright © 2005 John Wiley & Sons, Ltd.