Reaction Steps
Phenyl 1′-methyl-2′-oxo-1′,2,2′,3-tetrahydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indole]-4′-carboxylate (0.30 g, 0.70 mmol), cyclobutylamine hydrochloride (0.23 g, 2.1 mmol), potassium carbonate (0.39 g, 2.8 mmol) and N,N-dimethylformamide (3.0 mL) were added to a microwave reaction vessel. The reaction was heated at 110° C. for 1 h in a microwave reactor, allowed to cool to ambient temperature, poured into water (25 mL) and extracted with ethyl acetate (3×50 mL). The combined organic extracts were washed with 1 M hydrochloric acid (50 mL) and brine (50 mL), dried over magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by column chromatography and eluted with a 20% to 100% gradient of ethyl acetate in hexanes followed by recrystallization from dichloromethane/diethyl ether to afford N-cyclobutyl-1′-methyl-2′-oxo-1′,2,2′,3-tetrahydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indole]-4′-carboxamide (0.045 g, 17%) as a colorless solid: mp 128-129° C. (dichloromethane/diethyl ether); 1H NMR (300 MHz, CDCl3) δ 7.41-7.33 (m, 1H), 7.26-7.21 (m, 1H), 6.97-6.93 (m, 1H), 6.51 (s, 1H), 6.20 (s, 1H), 5.46 (d, J=6.65 Hz, 1H), 4.96-4.81 (m, 2H), 4.35-4.01 (m, 5H), 3.25 (s, 3H), 2.27-2.09 (m, 2H), 1.70-1.40 (m, 4H); MS (ES+) m/z 407.0 (M+1). N,N,1′-trimethyl-2′-oxo-1′,2,2′,3-tetrahydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indole]-4′-carboxamide (0.12 g, 37%) was isolated as a byproduct from the synthesis of N-cyclobutyl-1′-methyl-2′-oxo-1′,2,2′,3-tetrahydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indole]-4′-carboxamide, obtained as colorless solid: mp 218-221° C. (dichloromethane/diethyl ether); 1H NMR (300 MHz, CDCl3) δ 7.32 (dd, J=7.8, 7.8 Hz, 1H), 6.91-6.84 (m, 2H), 6.44 (s, 1H), 6.22 (s, 1H), 5.05 (d, J=8.8 Hz, 1H), 4.79 (d, J=8.8 Hz, 1H), 4.20-4.04 (m, 4H), 3.28 (s, 3H), 2.79 (s, 3H), 2.19 (s, 3H); MS (ES+) m/z 381.0 (M+1).
