Facile synthesis of functionalized quinolinones in a green reaction medium and their photophysical properties†

A facile and green chemical approach was successfully developed to construct functionalized quinolinones utilizing substituted alcohols, alkyl acetoacetate, and α-bromo ketones. Various quinolinones bearing either electron-rich or electron-deficient groups at different positions were synthesized in moderate to good yields under mild reaction conditions. The plausible mechanistic pathway for this transformation is supported by experimental evidence and control experiments. This simple approach for synthesizing quinolinones could open new avenues for discovering novel biological and pharmaceutical compounds. The use of affordable nickel catalysts, mild reaction conditions, operational simplicity, and high atom economy are attractive features of this method. Furthermore, the synthetic efficiency has been demonstrated through gram-scale experiments. Our research also provides valuable insights into the photophysical properties of the synthesized derivatives. Notably, compound 6n exhibited the highest Stokes shift (216 nm) in DCM solvent. Furthermore, compounds 5d and 6j showed positive solvatochromism, displaying a stronger emission as the solvent polarity increased. Additionally, compound 6j displayed aggregation-induced emission (AIE) properties in a DMSO : water mixture, making it suitable for use as a security ink, highlighting its potential applications in various fields.