摘要:
A process for the preparation of N-substituted maleimides by conducting heat-dehydration and dehydrating imidization of N-substituted maleamic acids under azeotropic distillation of generated water in a solvent mixture containing a solvent capable of forming water azeotrope and an organic aprotic polar solvent, in the presence as catalyst of metallic tin, tin oxide, a tin salt of a maleamic acid or a tin compound which forms a tin salt of the N-substituted maleamic acid in the reaction system. E.G. N-phenylmaleamic acid (produced in situ from aniline and maleic anyhydride) in xylene and dimethylformamide is converted to N-phenylmaleimide using as a catalyst stannous oxide (0.025 mole per mole of maleic anhydride).