(299f) Photon Mediated Coupling Reactions Using Copper Nanocatalysts - Molecular Mechanisms on Homo Coupling and Hetero Coupling Activity

Metal catalyzed coupling reactions are widely used reactions in the pharmaceutical industry. These reactions are traditionally executed using expensive, rare-earth palladium (Pd) based homogeneous catalysts. Copper nanocatalyst catalyzed cross-coupling reactions will have several advantages as they can be used as a platform to develop energy efficient and environmentally friendly flow processes. Recently, promising results have been reported in the literature on the use of metal nanocatalysts for coupling reactions. However, identifying the catalytic pathway (i.e., heterogeneous versus homogeneous pathway) remains a herculean task.

In this contribution copper nanocatalysts are used to perform cross-coupling and homo-coupling reactions. We demonstrate whether the catalyst utilizes the homogenous or heterogeneous pathway under different conditions. Molecular reaction mechanisms are proposed for both hetero and homo coupling activity and molecular structures for the intermediates are proposed. We will show how the reaction conditions determine whether the reaction is catalyzed by leached homogeneous complex or heterogeneous surface. Furthermore, by using a tunable light source with copper catalysts, we show an enhanced rate of reaction compared to the conventional thermally driven catalysis. We will discuss different possible mechanisms responsible for the photocatalytic activity.