5-Norbornene-2-carboxylic acid

6203-08-3

934-30-5

1. 0.510 mol (68.0 g) of anhydrous aluminum chloride was suspended in 660 mL of toluene. To the suspension was added 0.600 mol (51.7 g) methyl acrylate and stirred until the aluminum chloride was completely dissolved. 2. 0.600 mol (39.7 g) of newly cracked cyclopentadiene (dissolved in 340 mL of toluene) was added to the solution over 45 minutes. The reaction mixture was stirred at room temperature for 90 minutes and subsequently poured into water. 3. The toluene layer was washed with water, dried over anhydrous sodium sulfate, filtered and concentrated to dryness under vacuum. Purification by vacuum distillation over a Vigreux column afforded methyl 5-norbornene-2-carboxylate in 66.3 g (74%) yield and 99% purity (GC). 4. 5-Norbornene-2-carboxylic acid was prepared by mixing 164 mmol (25.0 g) of methyl ester with 85 g of 10% NaOH solution at 60 °C until the ester layer disappeared. Cool the solution, wash with ether, and 235 mL of 1 M hydrochloric acid at 60-70 °C with stirring. 5. The acid layer was separated, dissolved in ethyl acetate, washed with water, dried over anhydrous sodium sulfate, filtered and concentrated to dryness in vacuum to yield 18.2 g (80%). 1H and 13C NMR confirmed the product as 5-norbornene-2-carboxylic acid. 6. 132 mmol (18.2 g) of the acid was dissolved in 480 mL of dichloromethane and 2.66 mmol (0.205 mL) of N,N-dimethylformamide and 665 mmol (57.0 mL) of oxalyl chloride were added dropwise over 1 h. The reaction was purified by stirring for 1.5 h at room temperature. It was stirred at room temperature for 1.5 h. The solvent and excess oxalyl chloride were removed by evaporation under reduced pressure to give a brown oily residue in a yield of 18.1 g (88%). 7. 115 mmol (18.0 g) of chloroyl chloride was added to a mixture of diethylene glycol (57.5 mmol, 6.10 g) and pyridine (115 mmol, 9.09 g) and stirred at room temperature for 4 hours. 150 mL of dichloromethane and 100 mL of water were added and the organic layer was washed with water, sodium bicarbonate solution and hydrochloric acid solution and dried over anhydrous sodium sulfate. Filtered and concentrated to dryness to give a yellow oily residue in a yield of 18.9 g (95%). 1H and 13C NMR showed it to be predominantly a diester. 8. 54.5 mmol (18.9 g) of the diester was dissolved in 260 mL of dichloromethane. 15.3 mmol (2.08 g) of sodium acetate trihydrate was dissolved in a 39% peracetic acid solution of acetic acid (153 mmol, 29.8 g) and added dropwise to the diester solution over 30 minutes. The reaction mixture was stirred at room temperature for 4 h. The reaction mixture was washed with water and sodium bicarbonate solution. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated to dryness to give light yellow oily diethylene glycol di(5,6-epoxy-2-norbornanecarboxylate) in 19.8 g (96%) yield and 94% purity (GC).1H and 13C NMR confirmed the structure of the product.