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50 g of 1,2-cyclopentanedioic acid and 15 g of formamide were mixed, and after nitrogen substitution, the temperature was raised to 170 ° C. to react with At the same time steamed low boilers, the reaction measured by HPLC method when the control material is less than 0.2percent, the reaction was terminated; Cooling to 80 ° C, adding 50g of purified water and 0.5g of activated carbon, stirring at 50 ° C for half an hour, filtering by hot filtration, cooling the filtrate to 20 ° C, extracting with dichloromethane, concentrating the organic phase to dry 90 ° C without fraction, adding 100g toluene, The mixture was cooled to 5 ° C and dried under reduced pressure at 40 ° C to obtain about 60.6 g of white crystals in a yield of 93.5percent and a purity of 99percent or more and a content of 98percent or more.
Reference:
[1] Patent: CN106866495, 2017, A, . Location in patent: Paragraph 0016; 0017; 0018; 0019; 0020
50 g of 1,2-cyclopentanedioic acid and 15 g of formamide were mixed, and after nitrogen substitution, the temperature was raised to 170 C. to react with At the same time steamed low boilers, the reaction measured by HPLC method when the control material is less than 0.2%, the reaction was terminated; Cooling to 80 C, adding 50g of purified water and 0.5g of activated carbon, stirring at 50 C for half an hour, filtering by hot filtration, cooling the filtrate to 20 C, extracting with dichloromethane, concentrating the organic phase to dry 90 C without fraction, adding 100g toluene, The mixture was cooled to 5 C and dried under reduced pressure at 40 C to obtain about 60.6 g of white crystals in a yield of 93.5% and a purity of 99% or more and a content of 98% or more.