Hydrochloric Acid → 1-(10-Methyl-5,6,7,8,9,10-hexahydropyrido[3',2':4,5]pyrrolo[2,3-d]azepin-2-yl)-4-(5-(trifluoromethyl)pyridin-2-yl)pyridin-2(1H)-one hydrochloride

1.25 M HCl in MeOH (3.0 mL) was added to tert-butyl 10-methyl-2-(2-oxo-4-(5-(trifluoromethyl)pyridin-2-yl)pyridin-1(2H)-yl)-5,8,9,10-tetrahydropyrido[3′,2′:4,5]pyrrolo[2,3-d]azepine-7(6H)-carboxylate (32 mg, 0.060 mmol), and the resulting solution was stirred under N2 at ambient temperature for 18 h. The solution was concentrated under reduced pressure, the resulting residue was diluted with MeOH (1 mL) and Et2O (10 mL), and the solids were collected by filtration to provide the title compound (31 mg, quant.) as a yellow powder: mp 310-314° C. dec; 1H NMR (500 MHz, DMSO-d6) δ 9.19 (s, 2H), 9.15 (dd, J=1.0, 1.0 Hz, 1H), 8.41-8.35 (m, 2H), 8.09 (d, J=8.5 Hz, 1H), 8.05 (d, J=7.0 Hz, 1H), 7.43 (d, J=8.5 Hz, 1H), 7.30 (d, J=2.0 Hz, 1H), 7.12 (dd, J=7.0, 2.0 Hz, 1H), 3.76 (s, 3H), 3.42-3.40 (m, 2H), 3.36-3.32 (m, 2H), 3.30-3.28 (m, 2H, overlaps with H2O), 3.17 (t, J=6.5 Hz, 2H); ESI MS m/z 440 [M+H]+; HPLC (Method A) 98.83% (AUC), tR=13.9 min.