Synthesis of Well-Defined Copper N-Heterocyclic Carbene Complexes and Their Use as Catalysts for a “Click Reaction”: A Multistep Experiment That Emphasizes the Role of Catalysis in Green Chemistry

Abstract

A multistep experiment for an advanced synthesis lab course that incorporates topics in organic–inorganic synthesis and catalysis and highlights green chemistry principles was developed. Students synthesized two N-heterocyclic carbene ligands, used them to prepare two well-defined copper(I) complexes and subsequently utilized the complexes as catalysts in the Huisgen 1-3 dipolar cycloaddition of benzyl azide and phenylacetylene. The catalytic reaction exhibits high atom economy, is performed without a solvent at room temperature, and is high yielding. Thus, students were able to practice and apply concepts of green chemistry through catalysis. In the process of preparing ligands and complexes, several techniques were utilized that were aimed at performing reactions more efficiently (microwave experiments) or performing reactions in benign solvents (H2O). Another major component of this experiment is emphasis on technical writing through student preparation of formal communications and full paper using the formal ACS format.