General procedure for the synthesis of 2-methyl-5-benzothiazolecarboxaldehyde from (2-methylbenzo[d]thiazol-5-yl)methanol: To a stirred solution of (2-methylbenzo[d]thiazol-5-yl)methanol (0.6 g, 3.35 mmol) in anhydrous dichloromethane (6 mL) was added sodium bicarbonate (1.12 g, 13.4 mmol), followed by Dess- Martin periodate (2.84 g, 6.70 mmol). The reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the reaction mixture was diluted with dichloromethane (50 mL), washed sequentially with water (15 mL), 10% sodium bicarbonate solution (15 mL), and brine (15 mL), and dried over anhydrous sodium sulfate. After evaporation of the solvent, the target product 2-methyl-5-benzothiazolecarboxaldehyde was obtained. Yield: 99% (0.65 g, brown liquid). Product characterization data: 1H NMR (400 MHz, DMSO-d6): δ 10.12 (s, 1H), 8.25 (s, 1H), 7.80-7.79 (m, 2H), 2.86 (s, 3H). lcms (Method A): m/z 178.0 (M + H), retention time 2.84 min, purity 81.57% (maximum).
