1,2-Phenylenediamine

A dry, three-necked, round-bottomed flask is equipped with a condenser, thermometer, magnetic stirrer and is placed under a nitrogen atmosphere. Into the flask is placed 100 mL of dry 1,4-dioxane along with 5.4 g (0.05 mol) of 1,2-phenylenediamine and 9.9 g (0.061 mol) of Gold’s reagent. The mixture is refluxed overnight, cooled to room temperature and 4.1 g (0.05 mol) of anhydrous sodium acetate and 2 mL of glacial acetic acid are added. The resulting mixture is refluxed for 3 hours, cooled to room temperature and the solvent is removed in vacuo. The residue is taken up in chloroform (100 mL), extracted with a saturated, aqueous solution of sodium bicarbonate (3 x 50 mL) and dried over anhydrous magnesium sulfate. After removing the drying agent by filtration, the chloroform extract is concentrated in vacuo to leave a solid which is collected by vacuum filtration with the aid of a small amount (15 mL) of water. The resulting benzimidazole amounts to 3.7 g (63% yield).