A mixture of 6-chloropyridazin-3-amine (3.24 g, 25 mmol), methyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (9.8 g, 37.4 mmol), Pd2(dba)3 (0.72 g, 1.25 mmol), X-phos (1.19 g, 2.5 mmol) and Na2CO3 (7.95 g, 75 mmol) in dioxane (150 mL) and water (15 mL) was heated to 100° C. with stirring for 4 h under N2. The solvent was removed in vacuo and the resulting mixture was purified by chromatography (silica gel, 200-300 mesh, CH2Cl2:MeOH=20:1) to give methyl 4-(6-aminopyridazin-3-yl)benzoate (2.8 g, 48%) as a white solid. LC-MS: [M+H]+, 230.1, tR=1.213 min.
