Trifluoroacetic acid → 6-fluoro-5-morpholin-4-yl-3-(1H-pyrrol-2-yl)-1H-benzo[cd]indol-2-one

Participants

Reaction Steps

To a flask charged with 2-tert-butoxycarbonyloxy-4-[3-(1-tert-butoxycarbonyl-1H-pyrrol-2-yl)-3-oxo-prop-1-ynyl]-5-fluoro-indole-1-carboxylic acid tert-butyl ester (from Example 4 above) (220 mg, 0.39 mmol) was added morpholine (Aldrich, 2 mL, 23 mmol) and the red solution was stirred under argon at room temperature for 10 minutes. The reaction was then quenched by pouring the reaction mixture into an ice-cold saturated aqueous ammonium chloride solution (50 mL) and extracted with ethyl acetate (3×50 mL). The combined organic extracts were successively washed with water (50 mL) and brine (50 mL), dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue obtained was re-dissolved in CH2Cl2 (2 mL) and treated with trifluoroacetic acid at 0° C. for 1 hour. The reaction was then quenched with a saturated aqueous sodium bicarbonate solution (5 mL) and extracted with ethyl acetate (3×10 mL). The combined organic extracts were successively washed with water (5 mL) and brine (5 mL), dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The dark-brown material was then suspended in 0.5 N NaOH (8 mL) and heated to 90° C. for 6 hours. The reaction was quenched by pouring the reaction mixture into an ice-cold saturated aqueous ammonium chloride solution (10 mL) and extracted with ethyl acetate (3×20 mL). The combined organic extracts were successively washed with water (10 mL) and brine (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The crude product was purified by preparative TLC (silica gel, 50% ethyl acetate in hexanes) to afford 6-fluoro-5-morpholin-4-yl-3-(1H-pyrrol-2-yl)-1H-benzo[cd]indol-2-one as a yellow solid. (Yield 15.1 mg, 11.6%).

Provenance & Evidence