Triethylamine → 5H,7H-Imidazo[1,2-C]thiazole-2-carboxaldehyde

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反応手順

The solution of 2-bromo-3-isopropoxypropenal (6.9 g) in dry acetonitrile (326 mL) was added to the solution of crude thiazolidin-4-ylideneamine (3.3 g) in dry acetonitrile (326 mL) at room temperature. The reaction mixture was stirred at room temperature for 19.5 h, added triethylamine (4.9 mL) and then refluxed for 2 h. The reaction mixture was cooled to room temperature and then evaporated under reduce pressure. The residue was dissolved in dichloromethane (300 mL) and washed with 50% potassium carbonate aqueous solution (20 g). After filtration and separation, the aqueous layer was extracted with dichloromethane (50 mL×4). The organic layers were combined, dried (MgSO4) and filtered. The filtrate was evaporated under reduced pressure. The residue was applied to silica gel column chromatography and eluted with CHCl3-MeOH (100:3) to obtain crude 7H-Imidazo[1,2-c]thiazole-2-carbaldehyde as a brown solid. The crude product was re-crystallized twice from CHCl3-n-hexane (1St: 30:5, 2nd: 30:60) at 0° C. to give the required aldehyde as pale brown crystals (Yield: 1.84 g, 15%).

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