Pyridine → 10-Acetyl dithranol

Participants

Reaction Steps

To a solution of 56.5 g of purified anthralin (0.25 mole) in 1750 cm3 of anhydrous toluene, there are added, with stirring at ambient temperature, 27.3 cm3 of anhydrous pyridine (0.34 mole). There are then slowly added, using a dropping funnel, 21.4 cm3 of acetyl chloride (0.3 mole). There is produced during the course of this addition a slight exothermicity. After the end of the addition, the temperature of the reaction mixture is raised to 90° C. for about 1 hour. After cooling the reaction mixture there are added at 30°-35° C., 27.3 cm3 of pyridine and then slowly 21.4 cm3 of acetyl chloride. The mixture is stirred for 1 hour at 85°-90° C. After having verified that the anthralin has been transformed into the 10-acetyl derivative, the reaction mixture is brought to ambient temperature, then washed three times with water (250 cm3). The toluene phase is decanted, dried on sodium sulfate and then concentrated to about 300 cm3. This solution is then introduced into a silica gel column and eluted with toluene and a 1:1 toluene-methylene chloride mixture. The first fractions are collected and concentrated under a vacuum. The resulting solid is then recrystallized in toluene, yielding 21 g of bright yellow crystals of 1,8-dihydroxy-10-acetyl anthrone having a melting point of 146° C.

Provenance & Evidence