Potassium Hydroxide → 5-Nitro-3-(1,4-dioxaspiro[4.5]dec-7-en-8-yl)-1H-indole

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Reaction Steps

A solution of 5-nitroindole (38) (0.2 g, 1.233 mmol) in dry methanol (5 mL) was treated with KOH (0.56 g) at room temperature. After stirring for 10 min., 1,4-cyclohexanedione monoethylene ketal (0.48 g, 3.083 mmol) was added and the resulting solution was refluxed for 36 h. The reaction was brought to room temperature and solvent was evaporated. The crude product was diluted with water (25 mL) and product was extracted into ethyl acetate (2×25 mL). The combined ethyl acetate layer was washed with brine (20 mL) and dried (Na2SO4). The solvent was evaporated and crude material was purified by flash-column chromatography (ethyla acetate) to obtain compound 78 (0.25 g, 68%) as a solid. mp 175-177° C.; 1H NMR (CDCl3) δ 1.91 (t, 2H, J=6.6 Hz), 2.49 (brs, 2H), 2.49-2.66 (m, 2H), 3.96-4.00 (m, 4H), 6.12 (t, 1H, J=3.9 Hz), 7.22 (d, 1H, J=2.4 Hz), 7.32 (d, 1H, J=8.7 Hz), 8.05 (dd, 1H, J=2.1, 9.0 Hz), 8.36 (brs, 1H), 8.78 (d, 1H, J=2.1 Hz); ESI-MS m/z (%): 301 (M+, 100).

Provenance & Evidence