Method for synthesizing N-benzyl-4-piperidinecarboxylate

[0032] Add 1500g of dichloromethane into a 3000ml reaction flask, add 129.16g of 4-piperidinecarboxylic acid and 121.43g of triethylamine under stirring, and add 139.24g of benzyl chloride under temperature control below 20°C. After dropping, the temperature was slowly raised to reflux for 24 hours, the reaction solution was lowered to room temperature, and 600 g of water was added to stir evenly, and the liquid was separated; the organic layer was washed by adding 300 g of saturated saline, and the organic layer was separated and dried; the obtained filtrate was filtered and concentrated to obtain the oil N-benzyl -4-piperidinecarboxylic acid 197.79g; molar yield 90.2%, liquid phase purity 96.53%.

[0034] Add 775g of 1,2-dichloroethane into a 2000ml reaction flask, add 129.16g of 4-piperidinecarboxylic acid and 155.1g of diisopropylethylamine under stirring, and add 139.24g of benzyl chloride under temperature control below 20°C. After dropping, slowly raise the temperature to 83.5°C for reflux reaction for 8.5h, then drop the reaction solution to room temperature, add 300g of water, stir evenly, and separate the liquids; add 150g of saturated saline to the organic layer, wash the organic layer, separate and dry the organic layer; - Benzyl-4-piperidinecarboxylic acid 201.52g; molar yield 91.9%, liquid phase purity 96.81%.

[0036] Add 775g of 1,2-dichloroethane into a 2000ml reaction flask, add 129.16g of 4-piperidinecarboxylic acid and 131.55g of triethylamine under stirring, and add 189.87g of benzyl chloride under temperature control below 20°C. After dropping, the temperature was slowly raised to 83.5°C for reflux reaction for 10 hours, the reaction liquid was lowered to room temperature, and 300 g of water was added to stir evenly, and the liquid was separated; the organic layer was washed by adding 150 g of saturated saline, and the organic layer was separated and dried; the obtained filtrate was filtered and concentrated to obtain an oily substance N- Benzyl-4-piperidinecarboxylic acid 201.96g; molar yield 92.1%, liquid phase purity 97.21%.