Reaction Steps
A heavy-walled Pyrex tube was charged with a solution of indole-7-carboxaldehyde (0.50 g, 3.44 mmol) in 1,2-dichloroethane (5 mL). This solution was treated with tert-butyl 4-(5,6,7,8-tetrahydroquinolin-8-ylamino)butylcarbamate, 3, (1.21 g, 3.78 mmol), sodium triacetoxyborohydride (1.46 g, 6.88 mmol) and a catalytic amount of acetic acid (2 drops). The reaction mixture was exposed to microwave irradiation for 10 min at a temperature of 100° C. After the irradiation, the reaction tube was cooled with high-pressure air until the temperature had fallen below 40° C. The crude reaction mixture was poured onto a saturated aqueous solution of sodium bicarbonate. The product was extracted with dichloromethane. The combined organic layers were washed with brine, dried over potassium carbonate, filtered and concentrated in vacuo. The crude product was purified by silica gel chromatography (0-5% methanol/CH2Cl2) to afford 0.54 g (35% yield) of the desired product 6: 1H NMR (400 MHz, CDCl3) δ 12.87 (bs, 1H), 8.56 (d, J=3.6 Hz, 1H), 7.53 (d, J=7.6 Hz, 1H), 7.41-7.37 (m, 2H), 7.10 (dd, J=5.2, 7.6 Hz, 1H), 6.97-6.88 (m, 2H), 6.51-6.49 (m, 1H), 4.26-4.20 (m, 2H), 3.96 (d, J=13.2 Hz, 1H), 3.60 (d, J=13.2 Hz, 1H), 2.92-2.72 (m, 3H), 2.65-2.55 (m, 2H), 2.50-2.40 (m, 1H), 2.29-2.20 (m, 1H), 2.14-2.04 (m, 1H), 1.95-1.68 (m, 2H), 1.47-1.15 (m, 2H), 1.39 (s, 9H); ESI+ MS: m/z (rel intensity) 449.2 (100, [M+H]+) Step b: Preparation of N1-((1H-indol-7-yl)methyl)-N1-(5,6,7,8-tetrahydroquinolin-8-yl)butane-1,4-diamine (B). A solution of tert-butyl 4-(((1H-indol-7-yl)methyl)(5,6,7,8-tetrahydroquinolin-8-yl)amino)butylcarbamate, 6, (0.27 g, 0.60 mmol) in methanol (5 mL) was treated with thionyl chloride (1 mL) at room temperature. The resulting mixture was stirred for 30 min. The reaction mixture was then concentrated and dried under reduced pressure to afford 0.26 g (87% yield) of the desired product, B: 1H NMR (400 MHz, d6-DMSO) δ 11.97 (bs, 1H), 8.44 (d, J=4.8 Hz, 1H), 7.59 (d, J=7.2 Hz, 1H), 7.53 (d, J=7.2 Hz, 1H), 7.48-7.40 (m, 1H), 7.35-7.20 (m, 2H), 6.98 (t, J=6.8 Hz, 1H), 6.44 (bs, 1H), 4.90-4.78 (m, 2H), 3.60-3.53 (m, 2H), 3.10-3.00 (m, 2H), 2.80-2.60 (m, 4H), 2.50-2.39 (m, 1H), 2.30-1.40 (m, 7H); ESI+ MS: m/z (rel intensity) 349.2 (100, [M+H]+).
