1631-25-0

Synthetic Communications, 20, p. 1607, 1990 DOI: 10.1080/00397919008053079

Notclassified

1. In a 100 L reactor equipped with a thermometer, water separator, cooler and stirrer, 40 kg of xylene was added as solvent. Subsequently, 2 kg of silica gel as carrier, 2 kg (17.3 mol) o-phosphoric acid, 30 g (0.19 mol) of zinc acetate and 30 g (0.14 mol) of 2,4-dimethyl-6-tert-butylphenol were added sequentially. 200 g (1.96 mol) of triethylamine was added to neutralize the reaction system, followed by the slow addition of 4 kg (43.0 mol) of cyclohexylamine over 5 min to form the amine salt. 2. 4.4kg of maleic anhydride was added to the reactor over 5 minutes. The reaction temperature was maintained at 140°C and the resulting water was removed by azeotropic distillation along with xylene through a water separator. The reaction was maintained at this temperature for 3 hours. 3. After 3 hours of reaction, an additional 200g of maleic anhydride was added and the reaction was continued for another 3 hours. Upon completion of the reaction, the reaction mixture was cooled to 30°C and the catalyst layer was removed by layer separation. 4. The xylene solution layer was transferred to a neutralization tank, 500 g of 5% aqueous sodium carbonate solution was added, stirred for 20 minutes and then allowed to stand for 20 minutes to stratify the solution. Separate and discard the aqueous layer. 5. Add 500g of water to the organic layer, stir for 20 minutes and leave for 20 minutes, separate again and discard the aqueous layer. 6. The purified organic layer was transferred to a concentration tank and gradually heated under reduced pressure to 50°C, 100°C and finally distilled at 20°C to remove xylene. After complete evaporation of the solvent, 7.1 kg of light white solid product was obtained. 7. The purity of the product N-cyclohexylmaleimide was 98% by liquid chromatography analysis, based on a 97% yield of cyclohexylamine.

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