Synthesis of the laser dyes, AC2F, and related compounds

The synthesis of the laser dye, AC2F, which is 2-oxo-6,9-dimethyl-4-trifluoromethyl-6,7,8,9-tetrahydro-2H-pyrano(2,3- b)(1,8)naphthyridine, in nine steps from readily available starting materials is described. AC3F, which is the homologous 6,8,9-trimethyl compound, is made in six steps. Several related azacoumarins and azaquinolones, which fluoresce in the range 393-482 nm in ethanol, have also been prepared. In addition, 2-oxo-6,9-demethyl-8-phenyl-4-trifluoromethyl-6,7,8,9-tetrahydro-2H- pyrano(2,3-b)(1,8)naphthyridine has been made from 7-hydroxy-1,4-dimethyl-2-phenyl-1,2,3,4-tetrahydro-1,8-naphthyridine and sulfonated to furnish a water-soluble fluorescer (473 nm).