Non-Magnetic and Magnetic Supported Copper(I) Chelating Adsorbents as Efficient Heterogeneous Catalysts and Copper Scavengers for Click Chemistry

Novel supported chelating adsorbents bearing diverse multidentate nitrogenated ligands with strong copper(I) affinities are easily prepared in non-magnetic and magnetic variants using silica and silica-coated magnetite nanoparticles as suitable supports and the aza-Michael-type addition of vinyl sulfones as the ligation tool. These adsorbents are versatile materials with applications in the copper-catalyzed alkyne-azide cycloaddition (CuAAC) click chemistry where their complexation abilities enable them to act either as heterogeneous click catalysts when used in their complexed form or as copper(I) scavengers when used in their uncomplexed form. In the first instance, they proved to be robust and efficient heterogeneous catalysts to promote click reactions using extremely low doses and showing negligible copper leaching, particularly in the case of the silica-based non-magnetic adsorbents, allowing a simple operational protocol for their rapid and easy removal by filtration or magnetic decantation and showing good recyclability properties. In their uncomplexed form, the non-magnetic chelating adsorbents are very efficient copper scavengers that are able to remove any traces of metal contamination and that can be applied in tandem with any heterogeneous supported copper(I) catalysts or as stand-alone copper removing system in any click protocol allowing the isolation of metal-free clicked compounds.