Chitosan‐Supported Copper(II) Schiff Base Complexes: Applications in Synthesis of 5‐Substituted 1H‐Tetrazoles and Oxidative Homo‐Coupling of Terminal Alkynes

Abstract

Two new Chitosan‐supported Schiff base complexes (CS@L1‐Cu) and (CS@L2‐Cu) have been synthesized. They are characterized by various spectroscopic and instrumental techniques such as Fourier transform infrared spectroscopy (FT‐IR), Ultravoilet‐visible spectroscopy (UV‐Vis), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Energy dispersiveX‐ray microscopy (EDX), Thermo gravimetric analysis/Differential thermal analysis (TGA/DTA), and atomic absorption spectroscopy (AAS) analysis.Thecomplex CS@L2‐Cu have been found to be efficient heterogeneous catalyst for the synthesis of 5‐substituted 1H‐tetrazoles from a series of oximes and sodium azide and also for oxidative homo‐coupling of terminal alkynes. The catalyst could be easily recovered from reaction mixture by simple filtration and recycled up to five times with no significant loss in its catalytic activity. The mercury poisoning test indicated that the catalysts are heterogeneous in nature. All products were isolated as white to off‐white and light yellow solids and characterized by1H and 13C NMR spectroscopy.

Graphene Oxide Immobilized Copper(II) Schiff Base Complex [GO@AF‐SB‐Cu]: A Versatile Catalyst for Chan‐Lam Coupling Reaction

“…The full range XPS spectrum of GO@AF‐SB−Cu is shown in the Figure a. The peaks at binding energy of 529.7 eV, 398.5 eV, 283.5 eV and 102.2 eV correspond to O, N, C and Si respectively ,. Moreover, the Figure b shows the binding energy peaks at 952.4 eV and 932.3 eV corresponding to the spin‐orbit splitting components of Cu2p 3/2 and Cu2p 1/2 along with a satellite peak at 941.7 that indicates the +2 oxidation state of copper metal in the GO@AF‐SB−Cu complex ,, …”

Green carbon–carbon homocoupling of terminal alkynes by a silica supported Cu(ii)-hydrazone coordination compound

“…19 Therefore, preparing and introducing new heterogeneous catalytic systems for the green synthesis of diacetylenes have a high impact on the synthesis of these important chemicals. 20 Supporting copper coordination compounds on the surface of insoluble materials (like silica gel or alumina) can be considered one of the most successful methods for the production of new heterogeneous catalysts. 21 Nevertheless, suitable materials and professional synthetic strategies should be employed for this matter, which makes it a difficult process.…”

Melamine‐Functionalized Chitosan: A New Bio‐Based Reusable Bifunctional Organocatalyst for the Synthesis of Cyanocinnamonitrile Intermediates and Densely Functionalized Nicotinonitrile Derivatives

“…[24][25][26][27][28] Along these lines, several efforts have been reported to prepare functionalized derivatives of chitosan by chemical modification. [22,[29][30][31] The high content of nitrogen, oxygen or sulfur of the modifier compounds [29,[32][33] which form new bonds with the amino or hydroxyls groups has enabled their use not only as macro-chelating ligands for active metal catalysts [34][35][36] but also as direct organocatalysts. [37] Melamine (Me) is also an inexpensive chemical intermediate basically used to manufacture amino resins and plastics.…”

“…Along these lines, several efforts have been reported to prepare functionalized derivatives of chitosan by chemical modification ,. The high content of nitrogen, oxygen or sulfur of the modifier compounds, which form new bonds with the amino or hydroxyls groups has enabled their use not only as macro‐chelating ligands for active metal catalysts but also as direct organocatalysts …”