Pyrogallol → 2-Ethoxy-benzo[1,3]dioxol-4-ol

Participants

Reaction Conditions

Reaction Steps

A 500 mL round bottom flask was charged with pyrogallol (25 g, 0.198 mol), triethyl orthoformate (40 mL, 35.6 g, 0.240 mol), toluene (250 mL) and Amberlyst-15 (2.40 g). A 40 cm long B24 reflux condenser was attached and on top of this a distillation head was connected to a condenser, receiver adaptor and 100 mL collecting flask. The reaction mixture was stirred and heated under reflux at a metal block temperature of 150° C. for 1 h. The water flow to the is reflux condenser was stopped and the water to the distillation condenser was turned on. Distillate boiling point up to 78° C. was collected over 4 h, after which the block temperature was increased to 260° C. for 30 min and finally 170° C. for 30 min. The toluene/ethanol azeotrope (43 mL) was collected and contained 68% ethanol. The red mixture was filtered through celite and the filtrate was evaporated to dryness. The residue was absorbed onto 60 mL of flash silica then applied to a column of 300 mL flash silica made up in heptane/EtOAc (9:1). Elution with this solvent mixture afforded 37 (26.2 g, 73%) as a very pale yellow oil:

Provenance & Evidence