* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
Stage #1: 4-Bromo-2-methylaniline With thionyl chloride; methanesulfonamide In toluene at 120℃; for 18h; Inert atmosphere;
Stage #2: With pyridine In toluene at 120℃; for 18h; Inert atmosphere;
26.1 Step 1: 5-bromo-2,1-benzothiazole
A mixture of methanesulfonamide (7.2 g, 75.3 mmol), thionyl chloride (8.0 mL, 110 mmol) and toluene (10 mL) was stirred at 120° C. for 18 hours under N2. After cooling to rt, toluene was removed under reduced pressure and the residue was used directly in the next step. To a solution of 4-bromo-2-methyl-aniline (2.0 g, 10.8 mmol) in toluene (40 mL) was added Thionyl chloride (1.4 g, 11.8 mmol) drop wise at 0° C. After the addition was complete, the reaction mixture was heated at 120° C. for 18 hours. Pyridine (1.0 mL, 12.3 mmol) and the crude residue from the above reaction were added to the mixture. The resulted solution was then stirred at 120° C. for 18 h. The reaction mixture was concentrated under reduced pressure, dissolved in EtOAc (100 mL), and washed with water (2*100 mL). The organic layer was washed with brine (100 mL), dried with Na2SO4 and concentrated in vacuum to give the crude product which was purified by column chromatography on silica gel (EA: PE=1:10) to give 5-bromo-2,1-benzothiazole (800 mg, 3.74 mmol, 35% yield) as a yellow solid. LCMS calcd. for C7H5BrNS (M+H)+ m/z=214.0/216.0; found: 214.1/216.2.