Azide-Assisted Growth of Copper Nanostructures and Their Application as a Carbon Supported Catalyst in Two-Step Three-Component Azide–Alkyne Cycloadditions

Copper nanostructures were obtained from the reduction
of Cu(I)
under mild conditions in ethanol/water using sodium-l-ascorbate
and sodium azide while performing an amination reaction. When the
halobenzene substrate was reacted in the presence of a bulk carbon
black (CB) support, clustered copper sub-micrometer particles (SMPs)
and microparticles (MPs) form. The growth conditions of the MPs were
optimized, and the supported nanostructures were isolated and characterized
by scanning electron microscopy, energy dispersive X-ray spectroscopy,
thermogravimetry, and inductively-coupled plasma mass spectrometry.
The particles are mobile and supported within the CB matrix and proved
to be active catalysts in the azide–alkyne cycloaddition (CuAAC).
The catalytic competency of the particles was assessed in a two-step
three-component azide–alkyne cycloaddition of benzyl bromide,
sodium azide, and phenylacetylene as a model reaction. The reaction
conditions were optimized, and the optimized conditions were applied
for the synthesis of triazole compounds with varying levels of functionalization.
The recyclability of the catalysts was investigated, depletion modes
were discussed, and the conditions were fine-tuned to reach good recyclability.
This demonstrates the broader applicability of the SMPs/MPs as CuAAC-catalyst
and its limitations.