Boron tribromide → 3-Chloro-2-hydroxy-5-trifluoromethylbenzaldehyde

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Reaction Conditions

Reaction Steps

3-Chloro-2-fluoro-5-trifluoromethylbenzaldehyde (5.0 g, 22 mmol) was dissolved in dry CH3OH (50 mL), treated with 25% sodium methoxide solution (30 mL) and heated to reflux for 2 h. After cooling, the volatiles were removed by evaporation and the residue was taken up in H2O (20 mL) plus Et2O (80 mL). The aqueous phase was extracted with Et2O (50 mL), and the combined organic phases were washed with satd NaCl solution (15 mL), dried (Na2SO4) and evaporated. The residue was dissolved in dry CH2Cl2 (50 mL), cooled to −78° C. and treated with BBr3 (1 M solution in CH2Cl2; 25 mL, 25 mmol). After warming to 25° C., the mixture was stirred for 21 h, cooled to −40° C. and quenched by addition of H2O (30 mL). After warming, the aqueous phase was extracted with CH2Cl2 (30 mL), and the combined organic phases were washed with satd NaCl solution (30 mL), dried (Na2SO4) and evaporated. The residue was purified by silica gel chromatography with a 0-20% EtOAc gradient in hexane to give the purified aldehyde (2.7 g): 1H NMR (400 MHz, CDCl3) δ 11.81 (s, 1H), 9.96 (s, 1H), 7.87 (d, J=2.1 Hz, 1H), 7.84-7.77 (m, 1H); EIMS m/z 224.

Provenance & Evidence