Weigh 1.75g of vitamin B1 dissolved in 5mL of distilled water, another 10mL of 2-thiophenecarboxaldehyde and 10mL of 95% ethanol, and put them together in a three-necked flask with a refluxing condenser tube, and cooled in an ice-water bath. Add 5mL of triethylamine dropwise, the solution turned black. After addition, the ice-water bath was removed and replaced with an oil bath heated slowly and refluxed for 2 h. The solution was cooled to room temperature and neutralized with 10%
Hydrochloric acid to neutralize until the solution turns red, make up 15 mL of distilled water, and place in a refrigerator overnight. The liquid was decanted, the solid was washed with cold ethanol and recrystallized from ethanol to give 1.2g of slightly yellow crystals in 15% yield.
