To a solution of 6-chloro-2-methyl-4-(5-(piperidin-4-yl)pyridin-2-ylamino)pyridazin-3(2H)-one (200 mg, 625 μmol, Eq: 1.00) and acetone (799 mg, 1.01 ml, 13.8 mmol, Eq: 22) in MeOH (5 ml) was added sodium cyanoborohydride (39.3 mg, 625 μmol, Eq: 1.00) and acetic acid (656 mg, 625 μl, 10.9 mmol, Eq: 17.5). The reaction mixture stirred under N2 for 18 h. Additional acetone (1 ml) was added, followed by THF (3 ml). The reaction mixture continued stirring under N2 for 2 h. Additional sodium cyanoborohydride (19.7 mg, 313 μmol, Eq: 0.50) was added. The mixture stirred for 4 h. Concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 12 g, 50% to 100% (60:10:1 DCM:MeOH:NH4OH)/DCM gradient) to give 6-chloro-4-(5-(1-isopropylpiperidin-4-yl)pyridin-2-ylamino)-2-methylpyridazin-3(2H)-one (220 mg, 97%). LC/MS-ESI observed [M+H]+ 362.
