Tryptophol → 1,3,4,9-Tetrahydro-1-ethyl-pyrano[3,4-b]indole-1-acetic Acid Ethyl Ester

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Reaction Steps

A mixture of tryptophol (1.612 g, 10 mmol), ethyl propionylacetate (1.730 g, 12 mmol), and p-toluenesulfonic acid monohydrate (0.20 g) in benzene (70 mL) was heated to reflux for 5 hours. It was quenched with ethyl acetate and washed with saturated sodium bicarbonate. The organic layer was dried over magnesium sulfate, evaporated to dryness. Flash chromatography on silica gel provided 1.943 g (68%) of the title compound as a solid. mp<80° C. 1H NMR (300 MHz, CDCl3) δ 9.06 (br, 1H), 7.50 (d, 1H), 7.36 (d, 1H), 7.14 (t, 1H), 7.12 (t, 1H), 4.18 (q, 2H), 4.03 (m, 1H), 3.94 (m, 1H), 2.99 (d, 1H), 2.88 (d, 1H), 2.78 (m, 2H), 2.14 (m, 1H), 2.01 (m, 1H), 1.25 (t, 3H), 0.82 (t, 3H); ESI (+) MS m/e=288 (MH+), ESI (−) MS m/e=286 (MH−).

Provenance & Evidence