Synthesis of 7-(Diethylamino)-Chromene-fused Quinolines and 7-(Diethylamino)-4-Amino-3-Formyl-Coumarin Derivatives, Structural Elucidation, and Photophysical Properties

Abstract

A series of 7-(diethylamino)-coumarin-based heterocycles have been designed and synthesized through the reaction of 7-diethylamino-4-chloro-3-formylcoumarins with arlyamines by a onepot acid-catalysed synthesis. By tuning the reaction time and temperature, this reaction provides a pathway to either fused coumarin-quinoline scaffolds (3, 4meta, 4para, 6, and 7) or unfused 7-diethylamino-4-amino-3-formyl-coumarins (8-12), all in moderate to good yields (58-87%). The fused derivatives (3-7) display unusual photophysical behavior in a wide range of solvents, whereas the unfused systems (8-12) are essentially non-emmissive. The photophysical studies of the 3-7 exhibit dual absorption bands centered around 350 nm and 420 nm, while the emission shows pronounced solvent dependence, with high florescence effeciency (Φ = 0.62-0.82) and large Stokes shifts (>2,000 cm-1). All compounds are fully characterized, and X-ray quality crystals of compounds 4para and 9ortho are also reported.