The general procedure for the synthesis of dimethyl 2,5-dibromoadipate from methanol and adipic acid was as follows: Thionyl chloride (323 g, 2.71 mol) was slowly added dropwise in 70 ml portions to adipic acid (197 g, 1.35 mol) in a three-necked, round-bottomed flask fitted with a reflux condenser and a constant-pressure dropping funnel at 80 °C for 2 hours. The reaction mixture was stirred until the escape of gas ceased, at which point some of the solid adipic acid remained incompletely dissolved. Subsequently, the addition of another 100 ml of thionyl chloride was continued dropwise over a period of 7 hours and heating was continued until the gas escape stopped completely. The reaction mixture was cooled to ice bath temperature and bromine (473 g, 2.96 mol) was slowly added dropwise, during which the formation of a white precipitate was observed. The white precipitate was collected by filtration and purified by recrystallization with methanol to give 253 g of white powdery product in 53% yield. The product was characterized by 1H NMR (400 MHz, CDCl3, δppm): 2.00~2.05 (m, 2H), 2.28~2.35 (m, 2H), 3.80 (s, 6H), 4.24~4.26 (t, 2H).
