Cu(II)-Schiff base complexes for sustainable catalytic applications

The global demand for energy and industrial production of the last twenty years has driven the need for more sustainable processes. In chemistry this has given birth to green chemistry, a series of practices aimed at reducing the environmental impact of a reaction while improving its efficiency and safety, and overall reducing costs and energy requirements. Among the twelve principles of green chemistry, catalysis plays a crucial role. While traditional catalytic reactions rely on expensive rare metals like Pd, Pt orqe Rh, their use is cause of concern because of their toxicity especially in large scale and pharmaceutical applications. Earth-abundant metals have thus emerged as valid alternatives, thanks to their lower cost and increased safety. In this work we report the use of Cu(II)-Schiff base complexes as catalysts for a variety of reactions. Copper is well known for its redox properties and in conjunction with Schiff bases, it can help to further stabilize transition states during a catalytic process. A series of newly designed complexes bearing imidazolium moieties has been found to effectively promote C-H activation of allylic and benzylic substrates using water as the reaction medium. This catalytic system, in addition of high activity and selectivity, allows for easy separation of products from the reaction mixture. Additionally, the metal complex can be recovered and recycled in successive reactions. The copper catalyzed C-H activation was explored using MD-DFT, to obtain an updated reaction mechanism that includes the effect of solvents and ligands. Copper can also substitute palladium in cross-coupling reactions; we report the use of our catalytic system in the Chan-Lam- Evans reaction to afford N-arylated products, important intermediates in the synthesis of pharmaceutical compounds.