Boron trifluoride etherate → Ethyl 5-bromo-1,3,4,9-tetrahydro-8-methyl-1-propylpyrano[3,4-b]indole-1-acetate

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Reaction Steps

To a solution of 4-bromo-7-methyl tryptophol (1.12 g, 4.41 mmol) and ethyl butyrylacetate (0.71 mL, 4.41 mmol) in CH2Cl2 (20 mL) was added BF3.OEt2 (0.56 mL, 4.41 mmol) dropwise at room temperature. The solution was stirred for 2 hours and then washed with saturated aqueous NaHCO3 (15 mL) and brine (15 mL). The organic phase was dried (Na2SO4) and filtered through a pad of silica gel. The filter cake was washed with additional CH2Cl2 and the combined organic layer was evaporated to provide 1.62 g (93%) of title compound as a white solid. 1H NMR (CDCl3): 300 MHz δ 9.33 (bs, 1H), 7.11 (d, J=7.65 Hz, 1H), 6.76 (d, J=7.65 Hz, 1H), 4.19 (m, 2H), 4.03 (m, 1H), 3.90 (m, 1H), 3.15 (m, 2H), 3.03 (d, J=16.6 Hz, 1H), 2.89 (d, J=16.6 Hz, 1H), 2.43 (s, 3H), 2.08 (m, 1H), 1.96 (m, 1H), 1.38 (m, 1H), 1.27 (t, J=7.14 Hz, 3H), 1.18 (m, 1H), 0.87 (t, J=7.29 Hz, 3H).

Provenance & Evidence