Diisopropylethylamine → 5-[4-(3,5-di-tert-butyl-4-hydroxy-phenylsulfanyl)-piperidine-1-sulfonyl]-1-methyl-1H-pyrrole-2-carboxylic acid methyl ester

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To a solution of 2,6-di-tert-butyl-4-(piperidin-4-ylsulfanyl)-phenol hydrochloride (Ex. 3c, 5.4 g) in 44 mL of THF at room temperature was added N,N-diisopropylethylamine (8.8 mL), followed by 5-chlorosulfonyl-1-methyl-1H-pyrrole-2-carboxylic acid methyl ester (4 g). The mixture was stirred at room temperature for 18 h and then diluted with ethyl acetate and washed twice with 1 N HCl (aq), and once with brine. After concentration of the organic extracts, the crude solid was triturated with 15% ethyl acetate in hexanes to give 4.5 g of 5-[4-(3,5-di-tert-butyl-4-hydroxy-phenylsulfanyl)-piperidine-1-sulfonyl]-1-methyl-1H-pyrrole-2-carboxylic acid methyl ester as an off-white solid, mp 181-183° C. 1H-NMR (300 MHz, CDCl3): δ 7.23 (s, 2H), 7.17 (d, 1H, J=1.5 Hz), 7.09 (d, 1H, J=1.2 Hz), 5.30 (s, 1H), 3.96 (s, 3H), 3.83 (s, 3H), 3.60-3.54 (m, 2H), 2.80-2.74 (m, 1H), 2.54-2.45 (m, 2H), 2.03-1.97 (m, 2H), 1.73-1.67 (m, 2H), 1.41 (s, 18H).

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