Acetic Acid → N-ethyl benzazepine

To a solution of the benzazepine (0.98 g, 3.9 mmol) from step E above in dichloromethane (50 mL) were added acetaldehyde (0.44 mL, 7.7 mmol), sodium triacetoxyborohydride (1.8 g, 8.3 mmol), acetic acid (0.2 mL), and 3 Å molecular sieves (1.0 g). The reaction solution was stirred at room temperature for 24 hours and then it was diluted with dichloromethane, washed with aqueous 1N sodium carbonate, dried over sodium sulfate and concentrated in vacuo. The crude product obtained was purified by flash column chromatography (dichloromethane to 95:4.5:0.5 dichloromethane/methanol/concentrated ammonium hydroxide) to give the desired N-ethyl benzazepine (0.53 g, 48%) as a yellow oil: 1H NMR (CDCl3, 500 MHz) δ 7.34 (t, J=7.5 Hz, 2H), 7.25 (t, J=7.5 Hz, 1H), 7.17 (d, J=7.5 Hz, 2H), 6.75 (d, J=2.5 Hz, 1H), 6.68-6.40 (br, 2H), 4.27 (d, J=8.5 Hz, 1H), 3.94 (d, J=13.5 Hz, 1H), 3.81 (d, J=14.5 Hz, 1H), 3.77 (s, 3H), 3.27-3.16 (br, 1H), 3.06-3.01 (m, 1H), 2.55-2.45 (m, 2H), 2.32-2.24 (m, 1H), 2.13-2.04 (br, 1H), 1.11 (t, J=7.0 Hz, 3H); ESI MS m/z 282 [M+H]+.