Convenient 'on-water' one-pot, synthesis of flavonols catalyzed by LiOH.H2O- and H2O2-mediated oxidation

摘要

Water is an eco-friendly and economical solvent in organic synthesis. The ultrasound-assisted chemical reactions have proven to produce a better yield than the existing traditional approaches. Flavonol scaffold is widely distributed in nature. Therefore, it becomes very important to explore and develop a newer method for their synthesis. In the present work, we have described the one-pot efficient synthesis of flavonol and its derivatives using the LiOH.H2O and H2O2 system. Herein we utilized an eco-friendly chemistry approach using ultrasound and water as a medium to afford flavonols in good yields. LiOH.H2O was found to be a mild base to generate the chalcone intermediate whereas H2O2 acted as an oxidizing agent to produce a flavonol as revealed by a mechanistic study using mass spectrometry and NMR spectroscopy. This one-pot synthesis of flavonols is an effective alternative to the existing methods with the advantages of utilizing mild base and oxidant, ease in isolation, economical, eco-friendly, and good yields.