Sulfonated polynaphthalene as an effective and reusable catalyst for the one-pot preparation of amidoalkyl naphthols: DFT and spectroscopic studies

Sulfonated polynaphthalene (S-PNP) as a carbon-based solid acid efficiently catalyzed the one-pot three component synthesis of amidoallcyl naphthols. The three-component process of substituted aryl aldehydes, 2-naphthol, and amide (benzamide and acetamide) or urea in the presence of S-PNP under thermal solvent-free conditions is described. Short reaction times, high yields and easy work-up are the advantages of this protocol. Furthermore, the catalyst can be readily recycled and reused without obvious significant loss of activity. Also, density functional theory (DFT) with the aid of M06-2X and B3LYP methods was used for studying of the optimized structure, molecular orbitals, electrostatic potential (ESP) map and spectroscopic analysis of some selected amidoalkyl naphthols. The thermochemical parameters of reactions including enthalpy, internal energy, entropy and Gibbs free energy were also investigated. The theoretically calculated infrared (IR) and H-1 nuclear magnetic resonance (NMR) spectra of title compounds were compared to the experimental data. Based on the results, the synthesis of amidoalkyl naphthols is exothermic. A good consistency between the calculated and observed spectral data was found. (C) 2017 Elsevier B.V. All rights reserved.