Hydrochloric Acid → 2-Bromoimidazo[5,1-b]thiazole

Participants

Reaction Conditions

Reaction Steps

2-Bromoimidazo[5,1-b]thiazole-7-carboxylic acid (0.52 g, 2.10 mmol) was suspended in a mixed solvent composed of water (4.0 ml) and acetic acid (6.0 ml). Concentrated hydrochloric acid (0.30 g, 3.04 mmol) was added to the suspension at room temperature, and the mixture was stirred at 105° C. for about 19 hr. After the completion of the reaction, sodium carbonate (0.44 g, 4.15 mmol) was added to the reaction solution, and the mixture was concentrated by removal of the solvent by distillation under the reduced pressure. Water (10 ml) was added to the concentrate. Further, the solvent was removed by distillation under the reduced pressure, and water (10 ml) and ethyl acetate (5 ml) were again added thereto. The mixture was adjusted to pH 6 by the addition of a 2 M aqueous solution of sodium hydroxide with stirring. After the separation, the aqueous layer was extracted twice with 5 ml of ethyl acetate. Thereafter, the organic layers were combined and were washed with 15 wt % brine (5 ml). While concentrating the washed organic layers, the solvent was replaced with methanol (3 ml), and 10 ml of water was added thereto to crystallize 2-bromoimidazo[5,1-b]thiazole. The crystallizing liquid was cooled to 5° C. or below and was stirred overnight. The crystals were then collected by filtration. The resultant precipitate was dried under the reduced pressure to give 2-bromoimidazo[5.1-b]thiazole (0.39 g, yield 91.4%) as a white solid.

Provenance & Evidence