N,N'-Bis(phenyl)benzamidine

Preparation

To a three-necked, round-bottomed flask equipped with a mechanical stirrer, dropping funnel, and condenser is added 90.0 gm (0.46 mole) of pure dry benzanilide (see Note a) and 95 gm (0.46 mole) of phosphorus pentachloride (see Note b). The mixture is stirred to reduce the lumps and then heated for ½ hr at 110°C and 1½hr at 160°C, or until the evolution of hydrogen chloride ceases. Then 36.4 gm (0.46 mole) of KOH-dried pyridine (see Note c) is added with stirring, followed by 42.4 gm (0.46 mole) of freshly distilled aniline. The reaction mixture is heated at 160°C for about 20 min to discharge the red color, cooled to about 90°C, and 250 ml of water is added dropwise to precipitate the product in granular form. The product is filtered and added to 500 ml of 28% aqueous ammonia. The mixture is stirred while gently warming for 1 hr, filtered, dried, and recrystallized from 80% ethanol (8-10 ml/gm product) to afford 73-80% product, m.p. 144-145°C.