General procedure for the synthesis of methyl 6-amino-3,5-dibromopyridine-2-carboxylate, methyl 6-amino-3-bromopyridine-2-carboxylate, and methyl 5-bromo-6-aminopyridine-2-carboxylate from methyl 6-aminopyridine-2-carboxylate: over a period of 30 min, a solution of chloroform (40 mL) with bromine (2.57 mL) was added slowly and dropwise to methyl 6-aminopyridine-2-carboxylate ( 6.92 g) in a solution of chloroform (300 mL). The reaction mixture was stirred overnight at room temperature. Upon completion of the reaction, the mixture was upsampled onto a silica gel column and purified by column chromatography (SiO2, heptane/ethyl acetate) to isolate three products: methyl 6-amino-5-bromo-pyridine-2-carboxylate (2 g, 19% yield), methyl 6-amino-3-bromo-pyridine-2-carboxylate (3 g, 29% yield) and methyl 6-amino-3,5-dibromopyridine-2-carboxylate (2.6 g, 18% yield).The 1H NMR (400 MHz, chloroform-d) data for methyl 6-amino-5-bromopyridine-2-carboxylate were as follows: δ 3.97 (s, 3H), 5.22 (br.s, 2H), 7.38 (d, J = 7.8 Hz, 1H), 7.79 (d, J = 7.8 Hz, 1H).
