Synthesis of a new copper(ii)-immobilized cross-linked chitosan biocomposite: its application as a heterogeneous catalyst in the synthesis of N-aryl propargylamines and their post-modification

Abstract

The development of heterogeneous catalysts for organic transformations is a fascinating area of contemporary research. In this work, a new 2,2′-(propane-1,3-diylbis(oxy))dibenzaldehyde (PDB) cross-linked chitosan-supported copper(II) nitrate biocomposite, CS-PDB@Cu(NO₃)₂, was synthesized and thoroughly analyzed by various spectroscopic techniques, such as FTIR, PXRD, XPS, FESEM, EDX, TGA, BET, and ICP-OES. The application of CS-PDB@Cu(NO₃)₂ was explored in the synthesis of N-aryl propargylamines from formaldehyde, anilines, and acetylenes (A3-couplings). The catalyst was retrieved from the reaction mixture by simple filtration and could be recycled for up to four catalytic cycles. Forty products were obtained in good to high yields (50–94%). (50–94%). Post-synthetic cyclization of N-aryl propargylamines, 3a, 3b, 3e, 3g, 3o, 3aa, 3ab, and 3ae, afforded C4-aryl quinolines 1–8 in excellent yields (82–98%). The reaction of N-aryl propargylamines 3a and 3m, with benzyl bromide and sodium azide, afforded N-benzyl-N-(3-phenylprop-2-yn-1-yl)aniline (9), and 3-phenyl-[1,2,3]triazolo[1,5-a]quinoxaline (10), respectively, in good yields. All isolated products were thoroughly analyzed by ¹H and ¹³C{¹H} NMR. The twenty-three new products, previously unreported, were also additionally characterized by HRMS. Additionally, the structure of propargylamine 3o, was determined by single-crystal X-ray crystallography.