Synthesis
The general procedure for the synthesis of 3-bromocatechol from 2-bromo-6-methoxyphenol was as follows: to an anhydrous dichloromethane (40 mL) solution of 2-bromo-6-methoxyphenol (8.00 g, 39.4 mmol) was slowly added boron tribromide (1 M in dichloromethane, 43.1 mmol, 43.0 mL) at -78 °C. The reaction mixture was stirred for 1 hour at room temperature, then poured into ice water and continued to stir for 30 minutes. Subsequently, extraction was performed with dichloromethane (3 x 30 mL). The organic layers were combined, dried with anhydrous magnesium sulfate, and concentrated to give the target product 3-bromocatechol (6.90 g, 93% yield) as a brown oil. Thin layer chromatography (TLC) analysis showed an Rf value of 0.2 (unfolding agent: toluene/ethyl acetate = 9:1). The 1H NMR data of the product were as follows: δH 5.60 (1H, broad single peak, OH), 5.69 (1H, broad single peak, OH), 6.72 (1H, double peak, J=8.1 Hz), 6.87 (1H, double peak, J=1.5,8.1 Hz), 7.00 (1H, double peak, J=1.5,8.1 Hz); 13C NMR data: δC 109.5, 114.9, 121.9, 123.3, 140.3, 144.5.The 1H NMR spectra of the products were in agreement with the literature reports.
References
[1] Organic Letters, 2016, vol. 18, # 15, p. 3726 - 3729
[2] Tetrahedron, 2011, vol. 67, # 34, p. 6308 - 6315
[3] Tetrahedron Letters, 1995, vol. 36, # 36, p. 6413 - 6414
