Triethylamine → hexane ethyl acetate 6-chloro-2-(4-bromobutyl)-2H-thieno[3,2-e]-1,2-thiazine 1,1-dioxide

The product from Step 1 (10.6 g, 28.3 mmol) was dissolved in tetrahydrofuran (anhydrous, 400 mL) and treated with triethyl amine (9.88 mL, 70.9 mmol) and methane sulfonic anhydride (9.86 g, 56.6 mmol) at room temperature and stirred for one hour. The suspension was concentrated and taken up in dimethylformamide (anhydrous, 120 mL). This mixture was heated at 160° for 45 min. The reaction mixture was poured into ice water (300 ml) and extracted with dichloromethane (300 mL). The organic layer was washed with water (2×200 mL), dried over magnesium sulfate and evaporated to a brown oil. After silica flash chromatography with hexane/ethyl acetate 6-chloro-2-(4-bromobutyl)-2H-thieno[3,2-e]-1,2-thiazine 1,1-dioxide was obtained as a yellow oil (4.97 g, 49%); the 1H NMR. was consistent with the structure.