Preparation
To a flask containing 17.5 gm (0.1 mole) of p-chlorobenzoyl chloride is added 50 ml (0.6 mole) of pyridine and the mixture heated for 5 min on the steam bath. The mixture is poured upon 100 gm of cracked ice and 50 ml of concentrated hydrochloric acid, allowed to warm to room temperature, filtered, the solid washed successively with 15 ml of methanol and 15 ml of dry benzene, and dried to afford 14.2-14.6 gm (96-98%), m.p. 192- 193°C (recrystallized from 250 ml of dry benzene).
Synthesis
GENERAL METHOD: Iodine (0.1573 g, 0.62 mmol) was dissolved in dichloromethane (2 mL) at 0 °C, followed by a one-time addition of triphenylphosphine (0.1626 g, 0.62 mmol). Next, p-chlorobenzoic acid (0.41 mmol) was added to the mixture, and triethylamine (0.17 mL, 1.23 mmol) was added at 0 °C. The reaction mixture was gradually warmed to room temperature and stirred continuously until the reaction was complete (usually about 10 minutes). Upon completion of the reaction, the crude product was concentrated under reduced pressure and subsequently purified by column chromatography (CC) using a hexane solution of 5-10% ethyl acetate as eluent to give the final 4-chlorobenzoic anhydride.
References
[1] Tetrahedron Letters, 2016, vol. 57, # 3, p. 325 - 328
[2] Synthesis, 1981, # 8, p. 616 - 620
[3] Tetrahedron Letters, 1986, vol. 27, # 41, p. 4937 - 4940
[4] Synthesis, 1981, # 3, p. 218 - 220
[5] Synthetic Communications, 1983, vol. 13, # 6, p. 471 - 488
