Ethanol → 5-Fluoro-3-(3-oxycyclopentyl)indole

Participants

Reaction Conditions

Reaction Steps

A mixture of 5-fluoroindole (6.0 g, 44.4 mmol) and 2-cyclopenten-1-one (4.5 mL, 53.3 mmol) in nitromethane (22 mL) was cooled to −20° C. in a carbon tetrachloride-dry ice bath. A mixture of boron trifluoride etherate (1.6 mL, 11.1 mmol) and ethanol (2.2 mL, 43 mmol) was added dropwise from an addition funnel. The reaction mixture was stirred at −20° C. for 2 hours, then was quenched with 5% aqueous sodium bicarbonate solution (100 mL), and extracted with ethyl acetate (3×200 mL). The combined organic layers were washed with water (100 mL) and brine (100 mL), then were dried over anhydrous sodium sulfate, filtered and concentrated to give 9.5 g of the title compound. Trituration with ethyl acetate afforded 5.6 g (58%) of the title compound as a yellow solid. An analytical sample was recrystallized from ethyl acetate/methanol: mp 119-120° C.; MS (ESI) m/z 218 [M+H]+.

Provenance & Evidence