Ethyl Acetate → N-(3,4-Dimethyl-5-isoxazolyl)benzo[b]thiophene-2-sulfonamide

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Reaction Steps

3,4-Dimethyl-5-amino-isoxazole (0.224 g, 2.0 mmol) and 50 mg of DMAP were stirred in 5 ml of pyridine at 25° C. The benzo[b]thiophene-2-sulfonyl chloride (0.16 g, 2.6 mmol) was added and the dark brown-yellow reaction mixture was stirred for 18 h at ambient temperature, poured into 100 ml of ethyl acetate and washed with 2% HCl (3×50 ml). The organic phase was dried with MgSO4, filtered and concentrated to collect 0.61 g of a brown oil/solid. The brown oil/solid was subjected to flash chromatography (30% ethyl acetate/hexanes) to provide 0.37 g of a light brown solid. This was stirred in 10 ml of methanol and 0.5 g of NaOH. The methanolic solution was heated for reflux for 1 h, then cooled to 25° C. and the methanol was removed in vacuo. The resulting residue was acidified to pH 1 with 2% HCl (100 ml) and extracted with ethyl acetate (2×50 ml) The organic phase was dried with MgSO4, filtered and concentrated to collect 0.225 g of a yellow-orange solid. This was recrystallized from CHCl3/hexanes to produce a light tan-yellow solid (0.194 g, 31% yield), m.p. 157-160° C.

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