Trifluoroacetic acid → N2-(3-(Dimethylamino)propyl)-N4-(piperidin-4-yl)quinazoline-2,4-diamine

tert-Butyl 4-(2-(3-(dimethylamino)propylamino)quinazolin-4-ylamino)piperidine-1-carboxylate (3.3 g, 7.71 mmol) in CH2Cl2 (20 ml) at 0° C. was added CF3COOH (4 ml, 53.9 mmol) and the reaction was stirred at room temperature overnight. The reaction mixture was then neutralized with 7 N NH3-MeOH. The resulting white solid was filtered away. The filtrate was concentrated and purified by silica gel column chromatography using 10% NH3 ca. 7 N MeOH in CH2Cl2 and 90% CH2Cl2 solution as eluent to obtain the title compound as a pure white solid.