反应详情

温度

-78 °C

The solution of boron tribromide in dichloromethane (1.0 M, 12.4 mL) in a 100-mL round bottom flask was cooled to −78° C., followed by the addition of 1.03 g of 3-(4-methoxyphenyl)-5-methylisothiazole-4-carboxylic acid as a solid slowly. The reaction mixture was stirred at −78° C. for 2 hrs. and at room temperature overnight. Water (20 mL) was added slowly, followed by the addition of 20 mL of 1.0 N NaOH and 100 mL of dichloromethane. The two layers were separated with a separatory funnel. The aqueous layer was acidified by the addition of concentrated hydrochloric acid. The product was extracted with ethyl acetate (3×100 mL). Solvent was evaporated in vacuo to give 0.935 g of 3-(4-hydroxyphenyl)-5-methylisothiazole-4-carboxylic acid (96%, theoretical yield 0.972 g). LCMS (method B) RT 2.28 min., MH+236. 1H NMR (500 MHz, CD3OD) δ 7.42 (d, J=8.5Hz, 2H), 6.80 (d, J=8.5Hz, 2H), 2.70 (s, 3H).

1. customat room temperature
2. customovernight
3. customThe two layers were separated with a separatory funnel
4. additionThe aqueous layer was acidified by the addition of concentrated hydrochloric acid
5. extractionThe product was extracted with ethyl acetate (3×100 mL)
6. customSolvent was evaporated in vacuo