General procedure for the synthesis of 2',3',4'-trihydroxyflavones using the compound (CAS: 7143-46-6) as starting material: flavone 13 (100 mg, 0.32 mmol, 1.0 equiv) was dissolved in 12 mL of dichloromethane. Boron tribromide (BBr3, 1.067 mL, 6.4 mmol, 20 eq.) was slowly added to the solution at room temperature and the reaction mixture was stirred for 48 hours. Upon completion of the reaction, the mixture was slowly poured into ice water and the precipitate formed was collected by filtration. The crude product was purified by fast column chromatography to afford 2',3',4'-trihydroxyflavone as a yellow amorphous solid (40 mg, 46% yield). The structure of the product was confirmed by the following characterization data: 1H NMR (400 MHz, DMSO-d6) δ: 10.02 (brs, 1H), 9.55 (brs, 1H), 8.89 (brs, 1H), 8.01 (dd, 1H, J = 1.5, 7.6 Hz), 7.78 (dt, 1H, J = 2.0, 7.6 Hz), 7.69 (d, 1H, J = 8.5 Hz), 7.45 (t, 1H, J = 7.5 Hz), 7.34 (d, 1H, J = 8.9 Hz), 7.11 (s, 1H), 6.54 (d, 1H, J = 9.0 Hz).13C NMR (125 MHz, DMSO-d6) δ: 117.5, 161.8, 156.1, 149.7 , 147.5, 134.2, 133.5, 123.4, 125.0, 123.6, 119.3, 118.6, 110.3, 109.5, 108.1. high-resolution mass spectrometry (HRMS) calculated value ([M + H]+) 271.0601, measured value 271.0597.
