[CH3:1][O:2][C:3]([C:5]1[CH:9]=[CH:8][O:7][C:6]=1[CH3:10])=[O:4].C1C(=O)N([Br:18])C(=O)C1>C(Cl)(Cl)Cl.C(O)(=O)C>[CH3:1][O:2][C:3]([C:5]1[CH:9]=[C:8]([Br:18])[O:7][C:6]=1[CH3:10])=[O:4](The following reaction is done under exclusion of light.) Dissolve 2-Methyl-furan-3-carboxylic acid methyl ester (22) (2.00 mL, 15.9 mmol) in chloroform (11 mL) and glacial acetic acid (11 mL) and add NBS (3.85 g, 21.6 mmol) portionwise in between a period of 75 min. Stir the reaction suspension for additional 16 h at rt. Add water to the reaction mixture and extract the aqu. layer with DCM (2 times), wash the combined organic layer with 2M aqu. NaOH, water and brine and dry it with Na2SO4 to obtain 5-Bromo-2-methyl-furan-3-carboxylic acid methyl ester (23) (2.80 g, 80%) as a red brown oil. No further purification. 1H NMR (400 MHz, CDCl3): 2.54 (s, 3H); 3.80 (s, 3H); 6.53 (s, 1H).
Wird geladen…
