In a 100 mL round-bottomed flask, 6-chloro-2-methyl-4-(5-(piperidin-4-yl)pyridin-2-ylamino)pyridazin-3(2H)-one (179 mg, 560 μmol, Eq: 1.00) and acetaldehyde (247 mg, 316 μl, 5.6 mmol, Eq: 10.0) were combined with THF (5.0 ml) to give a light yellow solution. Acetic acid (33.6 mg, 32.0 μl, 560 μmol, Eq: 1.00) was added. The reaction mixture was cooled to 0° C. Sodium triacetoxyborohydride (178 mg, 840 μmol, Eq: 1.5) was added. The reaction mixture stirred at room temperature for 2 h. The reaction was poured into water, and then saturated NaHCO3 was added to the solution until it was basic. The solution was extracted twice with EtOAc, and then the organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo to give a solid. The solid was triturated with ether to give 6-chloro-4-(5-(1-ethylpiperidin-4-yl)pyridin-2-ylamino)-2-methylpyridazin-3(2H)-one (121 mg, 62%). LC/MS-ESI observed [M+H]+ 348.
