Reaction Steps
In a 25 mL round bottom flask was placed 6′-bromospiro[cyclohexane-1,2′-indene]-1′,4(3′H)-dione (501 mg, 1.716 mmol) and it was dissolved in dichloroethane (5.7 mL). To this solution was added the trifluoro ethylamine (162 μL, 2.059 mmol), AcOH (124 μL, 2.059 mmol), and NaBH(OAc)3 (582 mg, 2.746 mmol) at last. The reaction was stirred at room temperature. When the reaction was completed it was quenched with saturated NaHCO3 (aq) (20 mL) and diluted with ethyl acetate (20 mL). The phases were separated and the aqueous phase was back-extracted with ethyl acetate twice (5 mL/each). The combined organic phases were dried over Na2SO4, filtered and concentrated under reduce pressure. The crude material was purified by flash chromatography (ISCO, 40 g SiO2 cartridge, ethyl acetate/hexanes as the eluents). At the end, two isomers were obtained and their corresponding fractions were combined separately and concentrated under reduce pressure yielding 6′-bromo-4-(2,2,2-trifluoroethylamino)spiro[cyclohexane-1,2′-inden]-1′(3′H)-one (axial, 97b) (420 mg, 1.120 mmol) and 6′-bromo-4-(2,2,2-trifluoroethylamino)spiro[cyclohexane-1,2′-inden]-1′(3′H)-one (equatorial, 98b) (108 mg, 0.288 mmol) (82% yield). Compound 97b: M+H=375.9, 1H NMR=(CDCl3, 400 MHz) δ 7.85 (d, J=1.6 Hz, 1H), 7.67 (dd, J=8.0, 1.6 Hz, 1H), 7.29 (d, J=8.0 Hz, 1H), 3.21 (q, J=9.2 Hz, 2H), 2.93 (s, 2H), 2.90 (m, 1H), 2.01-1.94 (m, 2H), 1.87-1.81 (m, 2H), 1.75-1.68 (m, 2H), 1.38-1.29 (m, 2H). Compound 98b: M+H=375.8, 1H NMR=(CDCl3, 400 MHz) δ 7.86 (d, J=1.6 Hz, 1H), 7.68 (dd, J=8.0, 1.6 Hz, 1H), 7.32 (d, J=8.0 Hz, 1H), 3.24 (q, J=9.6 Hz, 2H), 2.95 (s, 2H), 2.68 (m, 1H), 2.03-1.97 (m, 2H), 1.81-1.74 (ddd, J=14.0, 14.0, 3.6 Hz, 2H), 1.46 (m, 2H), 1.31-1.21 (m, 2H).
