Facile and Green One-Pot Synthesis of Fluorophore Chromeno[4,3-b]quinolin-6-one Derivatives Catalyzed by Halloysite Nanoclay under Solvent-free Conditions

Abstract

In this study, we demonstrated a straightforward method for the easy access of chromeno[4,3-b]quinolin-6-ones via a one-pot three-component reaction of 4-hydroxycoumarin, aldehydes and aryl amines in the presence of halloysite nanoclay as an eco-friendly, inexpensive and green heterogeneous catalyst under solvent-free conditions. Moreover, symmetric and unsymmetric bis-chromeno[4,3-b]quinolin-6-ones were obtained from dialdehyde or diamines in good yields by this method. To date, this is the first report on the synthesis of symmetric and unsymmetric bis-chromeno[4,3-b]quinolin-6-ones via such a one-pot, multicomponent reaction. Some prepared chromeno[4,3-b]quinolin-6-ones displayed as interesting fluorophore compounds, hereupon their fluorescence properties were considered. Good to excellent yields, short reaction times and avoidance of toxic solvents are the significant features of this green procedure. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim