Synthesis of furanochromones: a new step in improvement of fluorescence properties

New 3-hydroxychromone derivatives with a fused furan heterocycle (2-aryl-3-hydroxyfurano[3,2-g]chromones) have been synthesized. This was achieved by an important improvement in the synthetic procedure. Like their parent analogs, these new compounds exhibit two intensive fluorescence emission bands belonging to normal (N*) and tautomer (T*) excited-state forms. While the spectral position of the N* band remains unchanged, the T* band is shifted to longer wavelengths, providing larger separation between the two bands. The new compounds exhibit increased molecular extinction and, more importantly, have about twice as high fluorescence quantum yields. These properties make them very promising for designing new two-band fluorescence sensors.