Hydrochloric Acid → Benzenesulfonamide, 2-bromo-N-(4,5-dimethyl-3-isoxazolyl)-

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Reaction Steps

To 4,5-dimethyl-3-isoxazolamine (1.62 g, 13.00 mmol, prepared as described in T. Konoike et al., Tetrahedron Letters, 37, 3339 (1996)) and 4-dimethylaminopyridine (159 mg, 1.3 mmol) in 6.5 ml pyridine at 0° C., 2-bromobenzenesulphonyl chloride (3.65 g, 14.3 mmol) was added in portions over 10 minutes. After stirring at room temperature overnight, the mixture was added dropwise to 40 ml 6N HCl at 0° C. The mixture was extracted with 3×50 ml EtOAc. The combined organic extracts were washed with 30 ml each of 1N HCl and brine and dried and concentrated. The residue was dissolved in 160 ml MeOH and 160 ml 3% aqueous NaHCO3 solution was added and the mixture was concentrated in vacuo to remove most of the MeOH. The solid was filtered off and the aqueous filtrate was acidified to pH 2 with solid NaHSO4, and extracted with 3×100 ml of EtOAc. The extracts were washed with brine, dried and concentrated to give the title compound of this step (3.0 g, 70%). Rf=0.57, silica gel, 1:1 hexane/EtOAc.

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