Heteropoly acids as catalysts for preparation of N-(hydroxyphenyl)maleimide

INOR 673

Zhiping Le, lzping@ncu.edu.cn1, Yanqiu Huang, huangyanqiu@ncu.edu.cn1, Fei Yu2, Shaobo Deng2, Roger Ruan, ruanx001@umn.edu2, and Paul Chen2. (1) Department of Chemistry, Nanchang University, 999 Xuefu Road, Qianhu, Nanchang, 330031, China, (2) Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave, Saint Paul, MN 55108
N-Substituted maleimides are an important class of organic compounds with numerous applications in synthetic and polymer chemistry. Through the polyaddition reaction of maleimide, double bonds of N-Substituted maleimides are obtained in highly crosslinked networks with good thermal stability, fire resistance, low water absorption and biological properties. These are widely accepted as matrix resins for high-performance fiber-reinforced composite materials in the electronic, aviation and aerospace industries. N-(hydroxyphenyl)maleimides were synthesized via the condensation reaction between maleic anhydride and functional amines in this study. Heteropoly acids were used as catalysts for the cyclodehydration of the intermediate amic acid. The product was recrystallized from isopropanol and then characterized by its melting point, elemental analysis and Fourier Transform Infrared (FT-IR). The optimum reaction conditions were obtained by experimental designs. The results showed that the yield of N-(4-hydroxyphenyl) maleimide exceeded 94% under the experimental conditions of maleic anhyride to p-toluenesulfonate at 1.1:1(molar ratio), methylbenzene to N,N-dimethyl formamide at 10:1(volume ratio), phosphotungstic acid to 4-aminophenol at 0.0325:1(molar ratio), cyclodehydration reaction time for 2 hours. This work is supported by grants from the Jiangxi Provincial Department of Education of China (High Education & Technology) and the Jiangxi Provincial Natural Science Foundation of China (No. 0420032).