826-62-0

3813-52-3

The general procedure for the synthesis of 5-norbornene-2,3-dicarboxylic acid from nadic anhydride was as follows: in a 125 mL three-necked flask, 8 g of maleic anhydride and 26 mL of ethyl acetate were added, and the mixture was heated through a hot water bath until all solids were completely dissolved. Subsequently, 26 mL of petroleum ether (boiling range 60-90 °C) was added and the mixture was cooled to room temperature. Next, the mixture was further cooled using an ice water bath and 6 mL of freshly distilled cyclopentadiene was slowly added. The reaction mixture was placed in an ice-water bath with continuous stirring until a white solid precipitate precipitated, forming white needle-like crystals. The product was collected by diafiltration and washed with 15 mL of a mixture of ethyl acetate and petroleum ether. 12 g of Bicyclo[2.2.1]-2-heptene-5,6-dicarboxylic anhydride was finally obtained in about 84% yield with a melting point of 163.5-165.5 °C. 12 g of the above product was dissolved in 35 mL of 20% sodium hydroxide solution and heated to reflux for 1.5 h. The color of the solution changed from colorless to yellow. After continuing to reflux for 2 hours, the heating was stopped and cooled to room temperature. The reaction solution was transferred to a 100 mL beaker and filtered while hot. After the filtrate was cooled, it was acidified with concentrated hydrochloric acid to pH 2-3, and white needle-like crystals were precipitated. The crystals were collected by filtration and dried to give 10 g of 5-norbornene-2,3-dicarboxylic acid in 84% yield with a melting point of 167-168 °C.