Hydrochloric Acid → 9-Methyl(aminosulfonyl)fluorene-9-carboxylic acid ethyl ester

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A mixture of fluorene-9-carboxylic acid ethyl ester (1) (11 g, 46.2 mmoL), potassium carbonate (6.4 g, 46.2 mmoL, 1 eq) and a mixture of bromomethanesulfonamide and iodomethanesulfonamide [prepared from bromomethanesulfonyl chloride see, Trice et al., J. Org. Chem., 32, 990(1967) by reaction with ammonia gas in cold ether followed by reaction with excess sodium iodide in refluxing acetonitrile] (9.1 g, 1 eq) in dry dimethylformamide (100 mL, from sieves) was stirred under nitrogen for 18 h. Water (200 mL) was then added and the solution was acidified with 1N aqueous hydrochloric acid (100 mL) and extracted with ethyl acetate (3×100 mL). The combined organic phases were then washed with brine (3×200 mL), dried (MgSO4), and concentrated. The residue was purified by column chromatography on silica gel using 40% ethyl acetate in hexane to provide 4.8g (31%) of product (2): mp 150°-156° C.; IR (KBr) 3360, 1710, 740, 725 cm-1 ; 1H NMR (CDCl3, 200 MHz) 7.78-7.69 (m, 4 H), 7.50-7.32 (m, 4 H), 4.38 (bs, 2 H, exchangeable), 4.12 (q. 2 H), 4.11 (s, 2 H), 1.12 (t, 3 H), MS m/z 331 (M+), 178 (base peak).

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