General procedure for the synthesis of 2-bromo-5-formylthiazole from 2-bromothiazole-5-methanol: Manganese dioxide (3.8 g, 37.10 mmol) was added to a solution of 2-bromothiazole-5-methanol (1.44 g, 7.42 mmol) in trichloromethane (20 mL). The reaction mixture was stirred at room temperature for 3 days. Upon completion of the reaction, the mixture was filtered through diatomaceous earth and the filtrate was concentrated under reduced pressure to give 2-bromo-5-formylthiazole (870 mg, 61% yield) as a white solid. The structure of the product was confirmed by nuclear magnetic resonance hydrogen spectrum (1H-NMR, 400 MHz, CDCl3): δ 9.95 (s, 1H), 8.16 (s, 1H); nuclear magnetic resonance carbon spectrum (13C-NMR, 100 MHz, CDCl3): δ 180.93, 150.47, 145.48, 142.91; mass spectra (ESI): m/z 192.31 ([MH+]).
