4-Methoxybenzenesulfonyl chloride → 5-[(4-Methoxyphenyl)sulfonyl]-6-methyl-5,6-dihydrophenanthridine

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Reaction Steps

A stirred solution of phenanthridine (3.58 g, 20 mmol) in anhydrous diethyl ether (20 mL) was cooled to −30° C. and treated drop-wise under nitrogen via syringe with a solution of 1.4 M methyllithium in diethyl ether (14.5 mL, 20.3 mmol). The yellow solution was warmed to room temperature and stirred for 15 minutes. The mixture was cooled to −78° C. and treated with 4-methoxybenzenesulfonyl chloride (4.12 g, 20 mmol), as a solid, in a single aliquot. The reaction mixture was warmed slowly to room temperature over one hour, poured into 1 N aqueous sodium hydroxide, and extracted with ethyl acetate. The organic phase was washed sequentially with water, a 1 N hydrochloric acid solution, and a saturated, aqueous sodium chloride solution. After drying over anhydrous sodium sulfate, the organic phase was filtered through a short column of silica gel, and the filtrate evaporated in vacuo to yield a crude yellow oil (5.3 g, 73%). The crude oil was purified by preparative chromatography on a Biotage® 40 Mi column of pre-packed silica gel (90 g), eluting with a mixture of methyl tert-butyl ether-hexane (15:85) at a flow rate of 40 mL/min to afford, after evaporation of the solvent, a colorless oil. Crystallization of the colorless oil from a mixture of diethyl ether-hexane yielded the title compound (2.02 g, 5.6 mmol, 28%) as a homogeneous, colorless, crystalline solid, m.p. 167-169° C.;

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