Fluorescent 5H‐Pyrano[3,2‐c]chromenes: Synthesis, Photophysical Properties and Sensing of Nucleophilic Anions

Abstract

We report the development of a convenient organocatalytic method for the synthesis of 5H‐pyrano[3,2‐c]chromenes from chromone‐containing acrylates and ethyl cyanoacetate. The synthesis is characterized by simple conditions (ethanol, basic catalysis) and good yields (up to 90 %). The synthesized pyrano[3,2‐c]chromenes are a promising new class of fluorescent compounds. They have intense fluorescence in the yellow‐green region of the spectrum (495–554 nm) with high quantum yields (up to 72 %) and exhibit large Stokes shifts (3514–5856 cm−1). We have demonstrated the possible application of the obtained pyrano[3,2‐c]chromenes as selective “turn‐off” sensors for nucleophilic anions, such as cyanide, sulfide and sulfite.