Copper makes the difference: Developing Sustainable Photoredox Catalyzed Transformations

Synthetic organic chemistry undertakes significant efforts to develop new catalytic transformations that utilize greener reagents and avoid stoichiometric additives. In this regard, visible-light photoredox catalysis offers a unique activation mode of molecules, which serves as an alternative to many thermal transition-metals catalyzed reactions. The vast majority of photoredox-catalyzed processes capitalizes on heavy metals, namely, Ru(II) or Ir(III)-complexes which can serve as single electron oxidants or reductants in their photoexcited states. Copper-based photocatalysts are rapidly emerging, offering not only economic and ecologic advantages but, in addition, can interact with substrates beyond electron transfer via inner sphere mechanisms, which have been successfully utilized to achieve challenging transformations. Alternatively, polycyclic arenes or donor-acceptor complexes of substrates and reagents can promote photocatalytic transformations. Selected synthetic applications from our laboratory will be discussed, highlighting the complementary opportunities of copper and other inexpensive photocatalysts.