Thionyl chloride (1.0 mL) and DMF (1.0 mL) were combined and added dropwise to a mixture of 2-phenyl-1-(2-piperidin-4-ylethyl)-2,5-dihydro-4H-pyrazolo[3,4-c]quinolin-4-one (200 mg, 0.537 mmol) and dichloromethane (10 mL) at 0° C. The resulting suspension was stirred 5 minutes at 0° C. before warming to ambient temperature and stirring 55 minutes. The suspension was concentrated under reduced pressure to afford a light yellow oil that was stirred in acetonitrile and filtered to obtain a white solid. The solid was combined with additional acetonitrile and concentrated under reduced pressure to afford 100 mg of 4-chloro-2-phenyl-1-(2-piperidin-4-ylethyl)-2H-pyrazolo[3,4-c]quinoline.HCl as a white powder, mp 194° C. MS (APCI) m/z 391 (M+H)+; Anal. calcd for C23H23ClN4.1.0H2O.1.0HCl: C, 62.02; H, 5.88; N, 12.58. Found: C, 61.91; H, 5.67; N, 12.48.
