Synthesis of benzimidazoxanthenoisoquinolinones, new intermediates and dyes for synthetic-polymer fibres

The reaction of 4-chloronaphthalene-1, 8- dicarboxylic anhydride 3 with 2-n itrophenol in hot DMF and in the presence of copper powder as a catalyst gi ves 4 which is reduced to 5 with iron powder and glacial acetic acid. Compo und 5 is cyclized to 6. Condensation of benzo[k,l]xanthene-3, 4-dicarboxyli c anhydride 6 with o-phenylenediamine affords isemeric derivatives of new h eterocyclic benzimidszo[1,2-b]xantheno[2, 1,9-d e, f]isoquinolin-7-one 2a a nd benzimidazo[2, 1-a]xantheno[2, 1, 9-d, e, f]isoquinolin-8-one 2b. These are excellent new dyes for polyester filters, giving fluorescent orange to red dyeings of outstanding fastness to light and sublimation.