Synthesis of 6-(4-diethylamino)phenyl-2-oxo-2 H-pyran-3-carbonitorile derivatives and their fluorescence in solid state and in solutions

Abstract

One-pot synthesis of a new 2-pyrone dye ( 3a) by the reaction of 4-diethylamino-acetophenone ( 1) with methyl 2-cyano-3,3-bis(methylsulfanyl)acrylate ( 2) in the presence of sodium hydroxide as the base was carried out in DMSO. Compound 4a was synthesized by the replacement of methylsulfanyl group of 3a with dimethylamine at 4-position of pyrone ring. Similarly, compound 5a was prepared via the reaction of 3a with diethyl malonate. Compounds 3a–5a exhibited the following fluorescence in the solid state: red ( 3a), green ( 4a), and orange ( 5a). In addition, it was revealed that 2-pyrone dyes exhibit fluorescence in various solvents and show positive solvatochromism. Compounds 3a and 5a exhibited intense fluorescence in chloroform and dichloromethane (fluorescence quantum yield Φ: 0.94–0.95). In contrast, compound 4a exhibited intense fluorescence in polar solvents (methanol: Φ = 0.92). These 2-pyrone dyes have the potential for applications in various fields.