To a stirred solution of 3-(chloromethyl)-N-isopropyl-6-methoxyquinolin-2-amine hydrochloride SLA 28190 (305 mg, 1.01 mmol) in toluene (10 mL) in a 20 mL microwave vial equipped with a magnetic stirrer was added 6,7-dimethoxy-1-propylisoquinolin-3-ol RBO 35134 (250 mg, 1.01 mmol) followed by a 2 N aq. LiOH solution (1.01 mL, 2.02 mmol) and the mixture was stirred at 150° C. for 1.5 h under microwave irradiation. After cooling to RT, the mixture was diluted with CH2Cl2:MeOH=9:1 (150 mL), washed with brine (20 mL), dried over Na2SO4, filtered and concentrated at 40° C. under vacuum. Purification by column chromatography (SiO2, eluent EtOAc:MeOH=100:0 to 94:6) followed by a second purification by column chromatography (SiO2, eluent CH2Cl2:MeOH=100:0 to 95:5) provided 61 mg of 4-((2-(isopropylamino)-6-methoxyquinolin-3-yl)methyl)-6,7-dimethoxy-1-propylisoquinolin-3-ol as a brown solid. This free base was dissolved in CH2Cl2 (2 mL) in a 10 mL round-bottomed flask equipped with a magnetic stirrer before addition of a 0.49 M HCl solution in MeOH (1.05 mL). The reaction mixture was stirred for 5 min at RT then concentrated at 40° C. under vacuum to afford 4-((2-(isopropylamino)-6-methoxyquinolin-3-yl)methyl)-6,7-dimethoxy-1-propylisoquinolin-3-ol dihydrochloride 53 as a yellow solid (68 mg, 12% yield).
