Sodium Chloride → 2,7-dichloro-4-methyl-1,3-benzothiazole

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Reaction Steps

To a slurry of 2-amino-4-methyl-7-chlorobenzothiazole (77.2) (6.37 g) in H3PO4 (85%, 213 ml) in a 500 ml 3-necked flask with mechanical stirring and an internal temperature of <−10° C., was added dropwise a solution of NaNO2 (6.87 g) in water (11 ml). The mixture was warmed to 0° for 30 minutes and then recooled. The slurry was then slowly added to a cold (˜−5° C.) solution of CuSO4.5H2O (32 g) and NaCl (40 g) in water (128 ml) with vigorous mechanical stirring. After the foaming subsides and warming to RT, the solids were collected by filtration and rinsed with water. The solids were dissolved in ether leaving some insoluble residue. The ether solution was washed with water, and sodium bicarbonate solution. After the organic layer was concentrated, the residue was purified by flash chromatography with 10% methylene chloride in hexane to afford 2-chloro-4-methyl-7-chlorobenzothiazole (77.3) (4.48 g).

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