Reaction Steps
To a mixture of acetone (0.19 mL, 2.5 mmol) and 1,2-dichloroethane (5.0 mL), were added 1′-(piperidin-4-ylmethyl)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one hydrochloride (0.36 g, 0.84 mmol), triethylamine (0.35 mL, 2.5 mmol) and sodium triacetoxyborohydride (0.534 g, 2.52 mmol). The mixture was stirred at ambient temperature for 16 h and concentrated in vacuo. The residue was purified by column chromatography and eluted with ethyl acetate/methanol/ammonium hydroxide (20/1/0.2) to afford 1′-{[1-(1-methylethyl)piperidin-4-yl]methyl}-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one. To a solution of this compound in methanol (5 mL) was added a 4 M solution of hydrogen chloride in 1,4-dioxane (1.0 mL, 4.0 mmol) and the mixture was stirred at ambient temperature for 30 min and concentrated in vacuo. Sequential trituration of the residue in hexanes and diethyl ether afforded {[1-(1-methylethyl)piperidin-4-yl]methyl}-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one hydrochloride (0.21 g, 53%) as an off-white solid: mp 213-216° C.; 1H NMR (300 MHz, DMSO-d6) δ10.02-9.80 (br s, 1H), 7.40-7.02 (m, 4H), 6.51 (s, 1H), 6.18 (s, 1H), 4.74 (d, J=9.3 Hz, 1H), 4.62 (d, J=9.3 Hz, 1H), 4.23-4.06 (m, 4H), 3.73-3.21 (m, 4H), 3.00-2.78 (m, 2H), 2.20-1.52 (m, 5H), 1.32-1.12 (m, 7H); 13C NMR (75 MHz, DMSO-d6) δ176.8, 154.7, 144.0, 142.5, 137.7, 131.6, 128.7, 123.5, 122.8, 121.0, 111.1, 109.2, 98.6, 79.7, 64.1, 63.5, 57.1, 56.7, 47.1, 44.2, 32.1, 26.6, 26.4, 16.1; MS (ES+) m/z 435.1 (M+1).
