General procedure for the synthesis of 4-aminopyridine-2-carboxylic acid from 4-amino-3,5,6-trichloropyridine-2-carboxylic acid: a thick suspension formed by Picloram (8 g, 33 mmol) and 10% Pd/C (1.2 g) in a 10% aqueous LiOH solution (44 mL) was purged twice with hydrogen, and then under a hydrogen atmosphere (45 PSI) at 40°C for 4 hours with stirring. Subsequently, the mixture was heated to 70°C and maintained for 12 hours. Upon completion of the reaction, the cooled suspension was filtered through diatomaceous earth. The filtrate was acidified to pH=3 in concentrated HCl (~3.5 mL), at which point a precipitate was generated. The solid product was collected by filtration and dried overnight under high vacuum to give the final 4-aminopyridine-2-carboxylic acid as a beige solid (4.6 g, 99% yield).LCMS analysis showed m/z 139.1 (M + H)+ with a retention time of 0.21 minutes.
