New Dyes and Intermediates for Synthetic-polymer Fibres. 7,7-Dioxo-Benzo(k,l)thioxanthene-3,4-dicarboxylic Acid Imides

The synthesis of benzo[k,l]thioxanthene-3,4-dicarboxylic acid-7,7-dioxide is described. Condensation of this heterocycle with amines, or oxidation of the corresponding imides of benzo[k,l]tlhioxanthene-3,4-dicarboxylic acid, affords a new range of dyes which colour synthetic-polymer fibres, especially polyester, in yellow shades of excellent fastness to light and sublimation