Homogeneous and noncovalent immobilization of NHC-Cu catalyzed azide-alkyne cycloaddition reaction

Abstract

Abstract A series of new pyrene tagged nitrogen heterocyclic carbene copper (NHC-Cu) molecular complexes were synthesized and characterized by 1H- and 13C-NMR, high resolution ESI-mass spectrometry (HR-MS). The corresponding NHC-Cu complex was immobilized onto the surface of multi-walled carbon nanotubes (MWNTs) by using π-π stacking interaction, the noncovalent immobilization catalytic material MWNTs@NHC-Cu were characterized by FT-IR, XRD, XPS, thermogravimetry (TGA) and TEM. The new NHC-Cu complexes were tested both in the homogeneous phase and once immobilized onto multi-walled carbon nanotubes support for the azide-alkyne cycloaddition reaction. Both were active in the two-component click cycloaddition reaction of terminal alkynes and organic azides and three-component cycloaddition reaction that employs various terminal alkynes, NaN3 and organic halides with the advantage of excellent yields, low catalyst dosage, short reaction time. The MWNTs@NHC-Cu catalyst could be separated from the reaction system at the end of the reaction and reused in another catalytic cycle, but with loss of product yield.