Preparation of (-)-Levoglucosenone from Cellulose Using Sulfuric Acid in Polyethylene Glycol

Abstract

<i>(-)-Levoglucosenone (LGO, <b>1</b>)</i>. Polyethylene glycol 4000 (PEG) (200 g) (Note 2) is ground to a course powder (Figure 1) in a mortar (φ: 200 mm) and pestle (203 mm) and placed in a 500 mL beaker. A diluted solution of sulfuric acid (2.50 g, 25.5 mmol) in methanol (15 mL) (Note 3) is added at ambient temperature (22 °C) and the powder is mixed using a large spatula (18 cm) to distribute the acid into the powdered PEG and allowing most of the methanol to evaporate. Cellulose powder (50 g, 308 mmol of monomer) (Note 4) is added and the powders combined by stirring with the spatula for three minutes giving an intimate mixture of PEG/acid and cellulose powders (Figure 2). The powder mixture is transferred using a large powder funnel into a 1 L three-necked, round-bottomed flask. The left neck is equipped with a distillation head with the water-cooled Liebig condenser and 100 mL receiver flask. The center neck is equipped with a 29/32 cap, and the right neck is equipped with a thermocouple inserted through a 15/25 rubber septum (Figure 3). Two traps are connected to distillation setup. The first one is 100 mL two-necked flask and the second trap is a cold-finger. Each trap is cooled to -78 °C using a dry ice/methanol bath.