Synthesis
General procedure for the synthesis of 4-bromo-2-(trifluoromethoxy)phenol from 2-(trifluoromethoxy)phenol: A solution of bromine (1.55 mL, 30.3 mmol, 1.1 eq.) in dichloromethane (DCM, 50 mL) was added slowly and dropwise to a solution of 2-(trifluoromethoxy)phenol (5.0 g, 28.1 mmol, 1.0 eq.) in DCM at -78 °C ( 70 mL) solution. The reaction mixture was gradually warmed to room temperature and stirring was continued for 48 hours. Upon completion of the reaction, sodium thiosulfate (Na2S2O3-5H2O, 70 mL) solution was added and stirred until the orange color of the reaction mixture completely disappeared. Subsequently, the reaction mixture was diluted with DCM (100 mL), the organic phase was separated, washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was removed by evaporation under reduced pressure to give the crude product. Finally, the target product 4-bromo-2-(trifluoromethoxy)phenol was purified by silica gel column chromatography using 20% ethyl acetate-hexane as eluent in 74% yield.
References
[1] Journal of Medicinal Chemistry, 2002, vol. 45, # 14, p. 3112 - 3129
[2] Patent: WO2006/77364, 2006, A1. Location in patent: Page/Page column 88
[3] Patent: WO2006/77367, 2006, A1. Location in patent: Page/Page column 136
[4] Patent: WO2010/127208, 2010, A1. Location in patent: Page/Page column 59
[5] Patent: US2005/43300, 2005, A1. Location in patent: Page/Page column 44
