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Within the field of lignin biorefining, significant research effort has been dedicated to the advancement of catalytic methods for lignocellulose depolymerization. However, another key challenge in lignin valorization is the conversion of the obtained monomers into higher value‐added products. To address this challenge, new catalytic methods that can fully embrace the inherent complexity of their target substrates are needed. Here, we describe copper‐catalyzed reactions for benzylic functionalization of lignin‐derived phenolics via intermediate formation of hexafluoroisopropoxy‐masked para‐quinone methides (p‐QMs). By controlling the rates of copper catalyst turnover and p‐QM release, we have developed copper‐catalyzed allylation and alkynylation reactions of lignin‐derived monomers to install various unsaturated fragments amenable to further synthetic applications. [ABSTRACT FROM AUTHOR]

Inexpensive cobalt-catalyzed oxidative C-H functionalization has emerged as a powerful tool for the construction of C-C and C-Het bonds, which offers unique potential for transformative applications to modern organic synthesis. In the early stage, these transformations typically required stoichiometric and toxic transition metals as sacrificial oxidants; thus, the formation of metal-containing waste was inevitable. In contrast, naturally abundant molecular O 2 has more recently been successfully employed as a green oxidant in cobalt catalysis, thus considerably improving the sustainability of such transformations. Recently, a significant momentum was gained by the use of electricity as a sustainable and environmentally benign redox reagent in cobalt-catalyzed C-H functionalization, thereby preventing the consumption of cost-intensive chemicals while at the same time addressing the considerable safety hazards related to the use of molecular oxygen in combination with flammable organic solvents. Considering the unparalleled potential of the aforementioned approaches for sustainable green synthesis, this Review summarizes the recent progress in cobalt-catalyzed oxidative C-H activation until early 2020., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)