Trifluoroacetic acid → N4-(1-(3-fluorobenzyl)-1H-indazol-5-yl)pyrido[3,4-d]pyrimidine-4,6-diamine

To a stirred heterogeneous mixture of compound 211 (2.27 g, 4.48 mmol) and DCM (45 ml) was added trifluoroacetic acid (3.45 ml, 44.8 mmol), followed by anisole (0.99 ml, 8.96 mmol), and the mixture was stirred further at room temperature for 5 days. It was poured into petroleum ether (500 ml) and stirred at room temperature for ca. 20 min. Petroleum ether layer was decanted and discarded. The process was repeated with more petroleum ether (300 ml). To the solid left behind was added 5M NH3 (80 ml) at 0° C. and stirred at room temperature for 15 min. The solid was collected and washed successively with water (6×10 ml), petroleum ether-ethyl acetate=3:1 (3×20 ml), and dried to give N4-(1-(3-fluorobenzyl)-1H-indazol-5-yl)pyrido[3,4-d]pyrimidine-4,6-diamine (220) (1.68 g, 97%), mp 241-244° C.; 1H NMR δ [(CD3)2SO] 9.72 (s, 1H), 8.67 (s, 1H), 8.30 (s, 8.27 (br s, 1H), 8.15 (s, 1H), 7.75-7.68 (m, 2H), 7.41-7.33 (m, 14, 7.18 (s, 1H), 7.14-7.01 (m, 3H), 6.20 (s, 2H), 5.69 (s, 2H). Anal. Calcd for C21H16FN7.1.5H2O: C, 61.16; H, 4.64; N, 23.77. Found C, 61.23; H, 4.71; N, 23.87.