Hydrochloric Acid → 2,3-Dihydroxy-4-methoxybenzaldehyde

Beteiligte Stoffe

Reaktionsschritte

An anhydrous dichloromethane (500 mL) solution of 2,3,4-trimethoxy-benzaldehyde (6a, 19.6 g, 100 mmol) under argon at ambient temperature was stirred for 10 min and boron trichloride (100 mL, 100 mmol, 1 eq, 1.0 M soln in dichloromethane) was added. After 2 hours, the second equivalent of boron trichloride (100 mL, 100 mmol; 1 eq; 1.0 M solution in dichloromethane) was added. The dark reaction mixture was stirred for 24 hours, and then slowly poured into 10% sodium bicarbonate (aq) (40 g/360 mL). The resulting solution was acidified with concentrated hydrochloric acid to pH 1. The dichloromethane layer was separated, and the aqueous layer was extracted with ethyl acetate (4×100 mL) and dried. Evaporation of solvent in vacuo gave a brown oil, which was absorbed onto silica gel and subjected to flash column chromatography (50:50:1 hexane-ethyl acetate-acetic acid) to afford a yellow solid. Recrystallization from ethyl acetate-hexane gave yellow needles (12.4 g; 74%): m.p. 115-116° C. [lit. 116-117° C. (Pettit et al, 1987)]; Rf0.40 (1:1, hexane-ethyl acetate); EIMS m/z 168 (100%, M+), 125 (25%), 122 (40%), 79 (20%), 52 (20%). Anal. Calcd. for C8H8O4: C, 57.14; H, 4.80. Found: C, 57.23; H. 4.79.

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