Benzothiazole, 2,5-dimethyl- → 4-Bromo-2,5-dimethyl-1,3-benzothiazole

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Reaction Steps

A mixture of 2,5-dimethyl-1,3-benzothiazole (10.00 g, 61.26 mmol, Aldrich) and bromine (6.94 mL, 134.8 mmol) in chloroform (200 mL) was heated at reflux overnight. After cooling to room temperature, the mixture was washed with 1 N NaOH, followed by saturated sodium thiosulfate and brine, then dried over sodium sulfate and evaporated to dryness. The residue was purified on silica gel, eluting with 0 to 50% EtOAc in hexane. The first peak had a retention time of 2.51 minutes, LCMS calculated for C9H9BrNS(M+H)+: m/z=242.0; found: 241.9. 1H NMR shown to be the desired product B (980 mg, 6.61%). 1H NMR (CDCl3, 400 MHz) 7.63 (1H, d, J=8.4 Hz), 7.22 (1H, d, J=8.4 Hz), 2.87 (3H, s), 2.55 (3H, s) ppm. The second peak had a retention time of 2.758 minutes, LCMS (M+H)+m/z=241.9; found: 242. 1H NMR showed no coupling for the two phenyl hydrogens confirming the 6-bromo isomer.

Provenance & Evidence