[CH2:1]([C:3]1[C:12]([CH3:13])=[C:11]([O:14]C)[CH:10]=[CH:9][C:4]=1[C:5]([O:7][CH3:8])=[O:6])[CH3:2].B(Br)(Br)Br>C(Cl)Cl>[CH2:1]([C:3]1[C:12]([CH3:13])=[C:11]([OH:14])[CH:10]=[CH:9][C:4]=1[C:5]([O:7][CH3:8])=[O:6])[CH3:2]2.0 g of methyl 2-ethyl-4-methoxy-3-methylbenzoate are dissolved in 50 ml of DCM in a 100 ml round-bottomed flask, and BBr3 is carefully added dropwise at 0° C. The mixture is left to stir at RT for 4 hours. The solvent is distilled off in vacuo, methanol is carefully added to the residue at 0° C., and the mixture is evaporated again in a rotary evaporator. This operation is repeated a further twice, giving 1.88 g of methyl 2-ethyl-4-hydroxy-3-methylbenzoate as oil, which is employed for the next step without further purification; MS-FAB (M+H+)=195,2; Rf (polar method): 1.96 min.
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