Example A.1: 2-Bromomalonaldehyde (1.5 g, 9.94 mmol, 1 eq.) and thioacetamide (0.83 g, 11.05 mmol, 1.11 eq.) were suspended in dichloromethane (DCM, 10 mL) and the mixture was cooled to 0°C. Subsequently, N,N-diisopropylethylamine (DIPEA, 1.75 mL, 10.05 mmol, 1.01 eq.) was added slowly and dropwise. The resulting brown solution was stirred at room temperature for 3 days. After completion of the reaction, the organic phase was separated by diluting the reaction mixture with deionized water (50 mL). The aqueous phase was extracted three times with DCM (10 mL). The organic phases were combined, dried with anhydrous sodium sulfate (Na2SO4), filtered and concentrated. The brown residue was dissolved in ether (Et2O, 20 mL) and washed twice sequentially with saturated sodium bicarbonate solution (20 mL) and saturated saline (20 mL). The organic phase was dried again with anhydrous sodium sulfate (Na2SO4), filtered and concentrated to give pure 5-formyl-2-methylthiazole as a brown oil (0.40 g, 31% yield).
