Process for the preparation of 2-substituted and 2,3-disubstituted maleimides

A process for the preparation of substituted maleimides of the formula ##STR11## wherein R.sup.1 is an optionally substituted bicyclic or tricyclic aromatic ring in which one or more carbon atoms have been replaced by one or more nitrogen atoms and R.sup.2 is hydrogen, alkyl of a maximum of 8 carbon atoms, an optionally substituted monocyclic or bicyclic aromatic ring, or an optionally substituted monocyclic, bicyclic, or tricyclic aromatic ring in which one or more carbon atoms have been replaced by one or more nitrogen and/or sulfur atoms which comprises reacting an activated glyoxylate of the formula ##STR12## wherein R.sup.1 is as described above and X is a halogen atom, alkoxycarbonyloxy of a maximum of 8 carbon atoms in the alkoxy group, or pentafluorophenoxy, with an imidate of the formula ##STR13## wherein R.sup.2 is as described above, R.sup.3 is alkyl of a maximum of 8 carbon atoms, an optionally substituted monocyclic, bicyclic or polycyclic aromatic ring, or trialkylsilyl wherein the alkyl group is of a maximum of 8 carbon atoms, and Y is oxygen or sulfur, in the presence of a base and, after treating a reaction product obtained in which R.sup.2 is hydrogen or alkyl of a maximum of 8 carbon atoms, with a strong base, treating the resulting hydroxy-pyrrolinone of the formula ##STR14## wherein R.sup.1, R.sup.2, R.sup.3 and Y are as described above, with a mineral acid or an organic acid or by treatment with acylating agent and a suitable base, and recovering the resulting of formula I.