1,3-Dibromo-5,5-dimethylhydantoin → 7-(2-Bromo-1-fluoroethyl)-2-(3-fluoro-4-hydroxyphenyl)-1,3-benzoxazol-5-ol

Beteiligte Stoffe

Reaktionsschritte

Hydrogen fluoride pyridine (1.14 mL) was added dropwise into a cold (0° C.) solution of 2-[4-(acetyloxy)-3-fluorophenyl]-7-vinyl-1,3-benzoxazol-5-yl acetate (0.25 g, 0.7 mmol), in sulfolane (3 mL). The reaction mixture was stirred for 5 min and then 1,3-dibromo-5,5-dimethylimidazolidine-2,4-dione (120 mg) was added in one portion. The mixture was stirred at room temperature for 24 h, diluted with HCl (1N) and extracted with EtOAc. The organic layer was dried over MgSO4. Evaporation and purification by flash chromatography (CH2Cl2/isopropyl alcohol 0.3%) gave 7-(2-bromo-1-fluoroethyl)-2-(3-fluoro-4-hydroxyphenyl)-1,3-benzoxazol-5-ol as a white solid (0.25 g, m.p. 185–186° C.). The product was taken in acetonitrile (2 mL) and 1,8-diazabicyclo[5.4.0]undec-7-ene (150 mg) was added. The reaction mixture was stirred for 24 h, poured into cold (0° C.) HCl (1N, 10 mL) and extracted with EtOAc. The organic extracts were dried over MgSO4. Evaporation and purification by flash chromatography (20% EtOAc/hexanes) gave a white solid (160 mg, m.p. 213–214° C.); MS m/e 290 (M+H)+.

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