C[O:2][C:3]1[C:10]([O:11]C)=[C:9]([O:13][CH3:14])[CH:8]=[CH:7][C:4]=1[CH:5]=[O:6].B(Cl)(Cl)Cl.C(=O)(O)[O-].[Na+].Cl>ClCCl>[OH:2][C:3]1[C:10]([OH:11])=[C:9]([O:13][CH3:14])[CH:8]=[CH:7][C:4]=1[CH:5]=[O:6]An anhydrous dichloromethane (50 ml) solution of 2,3,4-trimethoxybenzaldehyde (1.96 g, 10 mmol) under argon at room temperature was stirred for 10 min and boron trichloride (10 ml, 10 mmol, 1 eq; 1.0 M solution in dichloromethane) was added. After 2 h, the second equivalent of boron trichloride (10 ml, 10 mmol, 1 eq; 1.0 M solution of dichloromethane) was added. The dark reaction mixture was stirred overnight and then slowly poured into 10% sodium bicarbonate (aq) (4 g/36 ml). The resulting solution was acidified with concentrated hydrochloride acid to pH 1. The dichloromethane layer was separated, and the aqueous layer extracted with ethyl acetate (4×20 ml) and dried. Evaporation of solvent in vacuum gave brown oil, which was further separated by column chromatography (1:1 hexane-ethyl acetate) to afford a yellow solid. Recrystallization from ethyl acetate-hexane gave a pale yellow needle of 48 (1.1 g, 65.5%); Rf0.40 (hexane:ethyl acetate: 1:1).
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