Formaldehyde → HCID 57950342, Verbindung

To a solution of 4-(benzyloxy)-1-(8-fluoro-5-methyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-7-yl)pyridin-2(1H)-one (100 mg, 0.26 mmol) in dichloromethane/acetic acid (1% acetic acid, 10 mL) were sequentially added formaldehyde (37% aqueous solution, 22 μL, 0.74 mmol) and NaBH(OAc)3 (316 mg, 1.49 mmol). The reaction mixture was stirred at room temperature for 2.5 h. The mixture was concentrated under reduced pressure, and the residue was dissolved in CH2Cl2. The organic layer was washed with H2O and 5% aqueous LiCl, dried over Na2SO4, filtered and concentrated. Purification by flash chromatography (silica gel, CH2Cl2/(10:1:0.1 CH2Cl2/MeOH/NH4OH), 0:1 to 1:1) gave 4-(benzyloxy)-1-(8-fluoro-2,5-dimethyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-7-yl)pyridin-2(1H)-one (78 mg, 38%) as a yellow solid. The free base was converted to the HCl salt using 1.25M HCl in methanol providing the title compound (75 mg, 95%) as a off-white solid: 1H NMR (300 MHz, CD3OD) δ 7.53-7.33 (m, 7H), 7.27 (d, J=10.5 Hz, 1H), 7.28 (dd, J=7.8, 2.4 Hz, 1H), 6.10 (d, J=2.7 Hz, 1H), 5.17 (s, 2H), 3.79 (br s, 2H), 3.67 (s, 3H), 3.03-3.00 (m, 4H), 2.64 (s, 3H); ESI MS m/z 418 [M+H]+; HPLC (Method A) 95.7% (AUC), tR=14.5 min.