Abstract 5. 6-Dihydro-p-dithiin-2. 3-dicarboxylic anhydride reacts with primary amines quite readily to form the substituted imides. The imide formation occurs much more easily than with maleic or phthalic anhydride. The imide and all N-substituted imides have a fairly strong, bright yellow colour. Their absorption spectra differ considerably from those of the anhydride, ester and dinitrile. Electron-attracting substituents on the imide nitrogen ...