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

Temperature

150 °C

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:

1. temperatureA 40 cm long B24 reflux condenser
2. customwas connected to a condenser
3. customreceiver adaptor and 100 mL collecting flask
4. temperatureheated
5. temperatureThe water flow to the is reflux condenser
6. customup to 78° C.
7. customwas collected over 4 h
8. temperatureafter which the block temperature was increased to 260° C. for 30 min and finally 170° C. for 30 min
9. customwas collected
10. filtrationThe red mixture was filtered through celite
11. customthe filtrate was evaporated to dryness
12. customThe residue was absorbed onto 60 mL of flash silica
13. washElution with this solvent mixture

ORD record

ord-0684071a6c3a462783fc12da19bda49d

Source dataset

uspto-grants-2012_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08198302B2