Trifluoroacetic acid → 3-Chloro-5-[(3-methoxyphenyl)sulfonyl]-6-methyl-5,6-dihydrophenanthridine

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A stirred solution of 3-chloro-6-methylphenanthridine (0.40 g, 1.76 mmol) in tetrahydrofuran (7 mL) was treated with freshly crushed sodium borohydride (0.33 g, 8.8 mmol). Trifluoroacetic acid (0.54 mL, 7.0 mmol) was added dropwise at a rate to keep the exothermic reaction and gas evolution under control. After the addition was complete the heterogeneous reaction mixture was stirred until the temperature returned to 23° C. The mixture was then heated at reflux for 14 hours. The reaction was cooled to room temperature and neutralized with a saturated, aqueous sodium bicarbonate solution (150 mL). The mixture was filtered through a plug of glass wool into a separatory funnel and extracted with diethyl ether (4×50 mL). The combined organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo to a light brown paste. The crude 3-chloro-6-methyl-5,6-dihydrophenanthridine was dissolved in pyridine (12 mL), treated with 3-methoxybenzenesulfonyl chloride (0.55 g, 2.64 mmol) and 4-(dimethylamino)pyridine (0.01 g, 0.08 mmol), and stirred at 80° C. for 14 hours. The reaction mixture cooled to room temperature, treated with a 0.1 N aqueous sodium hydroxide solution (100 mL, 10 mmol), and extracted with dichloromethane (6×50 mL). The combined organic phase was washed with a 2 N hydrochloric acid solution (2×40 mL), dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo to a brown solid. The brown solid was purified by flash column chromatography, eluting with a mixture of ethyl acetate:hexane (1:4), followed by crystallization from ethyl acetate-hexane, to afford the title compound as a homogeneous, white, crystalline solid (0.38 g, 54%), m.p. 117-118° C.;

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