Abstract: A process for forming perylene-3, 4-dicarboxylic anhydrides by reacting a corresponding perylene-3,4:9, 10-tetracarboxylic dianhydride with a sterically hindered amine, as a base, at an elevated temperature.

Abstract: Naphthalenelactamimides of the formula I ##STR1## in which, for example, R.sub.1 and R.sub.2 are 2,5-di-tert-butylphenyl and m and n are 0, are novel dyes which have the distinctive features of pronounced fluorescence as a solid and in solvents and a good light-fastness. They are therefore suitable, for example, for mass dyeing of high molecular weight organic material, as laser dyes and for the preparation of printing toners, colour filters, organic photoreceptors, electroluminescent and photoluminescent elements, optical information storage media or solar collectors. The compounds of the the formula I can be prepared by reaction of the corresponding naphthalenetetracarboxylic acid bisimides with a base.