[NH2:1][C:2]([CH3:6])([CH3:5])[CH2:3][OH:4].[Cl:7][C:8]1[S:12][C:11]([S:13](Cl)(=[O:15])=[O:14])=[CH:10][C:9]=1[N+:17]([O-:19])=[O:18].C(N(CC)CC)C.O>O1CCOCC1>[OH:4][CH2:3][C:2]([NH:1][S:13]([C:11]1[S:12][C:8]([Cl:7])=[C:9]([N+:17]([O-:19])=[O:18])[CH:10]=1)(=[O:15])=[O:14])([CH3:6])[CH3:5]
To a stirred solution of 2-amino-2-methyl-1-propanol (0.75 g, 8.39 mmol) in dioxane (21 ml) was added at room temperature 5-chloro-4-nitrothiophene-2-sulfonyl chloride (2.0 g, 7.63 mmol) and triethylamine (1.17 ml, 8.39 mmol). The light yellow suspension was stirred at room temperature for 17 h, poured into water (100 ml) and extracted with dichloromethane (3×75 ml). The combined organic layers were washed with water (100 ml) and brine (70 ml), dried (MgSO4) and evaporated. The crude product was further purified by column chromatography on silica gel (heptane/ethyl acetate 1:1) and subsequent crystallization from ethyl acetate/hexane to yield 5-chloro-4-nitro-thiophene-2-sulfonic acid (2-hydroxy-1,1-dimethyl-ethyl)-amide (0.73 g, 30%) as a light brown solid. MS (ISP) 313.1 [(M−H)−], mp 136° C.
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