Synthesis, Characterization, and Application of Natural Occurring Hydroxy Functionalized Benzoate based Ionic Liquids as Catalyst for 2-amino-7-hydroxy-4H-chromene Derivatives under Ultrasound Irradiation

Abstract

The Hydroxy functionalized benzoate based Ionic Liquids (ILs) were synthesized and characterized by Nuclear Magnetic Resonance (NMR), High-Resolution Electrospray ionization mass spectrometry (HR-ESI-MS), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Ultraviolet radiation (UV). All these techniques, especially NMR and HR-ESI-MS results, suggested the successful synthesis of the ILs. The electrical conductivity, viscosity, surface tension, density, and refractive index analyses of hydroxy-functionalized ILs were performed. The hydroxy-functionalized ILs were effectively employed in a one-pot synthesis of 2-amino-7-hydroxy-4H-chromene derivatives under ultrasound irradiation. These ILs demonstrated efficient catalytic performance, yielding 2-amino-7-hydroxy-4H-chromene derivatives in the 80 – 96 % range at 60°C. Upon completion of the reaction, the catalyst was easily recovered through simple filtration and reused for four additional cycles without significantly affecting product yields. Moreover, the impact of the supramolecular polymeric aggregation behavior of hydroxy-functionalized ILs on the catalytic activity was analyzed. The attained catalytic performance suggested that the synthesized catalyst is environmentally friendly, highly active, and suitable for synthesizing 2-amino-7-hydroxy-4H-chromene derivatives.