HATU (139 mg, 0.37 mmol) was added portionwise at ambient temperature to a stirred mixture of 3-[1-[3-(trifluoromethyl)[1,2,4]triazolo[4,3-b]pyridazin-6-yl]piperidin-4-yl]-1H-indole-5-carboxylic acid (150 mg, 0.35 mmol), 2-(methylamino)ethanol (0.034 mL, 0.42 mmol) and DIPEA (0.073 mL, 0.42 mmol) in DMF (2.0 mL). The resulting solution was stirred for 2 hours then purified by preparative HPLC (Waters XBridge Prep C18 OBD column, 5μ silica, 19 mm diameter, 100 mm length), using decreasingly polar mixtures of water (containing 1% ammonia) and MeCN as eluents. Fractions containing the desired compound were evaporated to dryness to afford N-(2-hydroxyethyl)-N-methyl-3-[1-[3-(trifluoromethyl)[1,2,4]triazolo[4,3-b]pyridazin-6-yl]piperidin-4-yl]-1H-indole-5-carboxamide (155 mg, 91%) as a colourless solid.
