Development of Synthetic Methods for the Late-Stage Modification of Synthetic Intermediates: The Arene-Limited Nondirected C–H Activation of Arenes and the Direct C–H Activation of Aliphatic Carboxylic Acids

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The transition to sustainable energy systems and chemical value chains based on renewable resources creates a continued demand for ever more efficient and resource saving synthetic methods, in order to meet the growing global demand for complex organic molecules such as drugs, pesticides, or parts of functional materials. In this context methods for the direct functionalization of carbon-hydrogen bonds are very attractive, since they hold the potential to shorten synthetic rouges and reduce waste production. Such methods are, however, challenging to develop, since the C–H bonds to be functionalized are chemically very stable and thus inert. At the same time typical organic molecules possess a variety of different C–H bonds, such that selectivity is all but trivial in such processes. Due to the substantial potential of C–H functionalization methods that still remains underexploited, such methods are at the center of substantial research efforts. The aim of this project is to study strategies for the palladium-catalyzed C–H activation of aromatic and aliphatic substrates, for which no suitable methods with sufficient reactivity and selectivity are currently available. For the functionalization of aromatic C–H bonds, we have recently discovered a catalyst system based on the use of two complementary ligands. We aim to use and conceptually further develop this approach for the functionalization of directing group-free aromatic substrates that can be employed as the limiting reagent. To functionalize aliphatic substrates, free carboxylic acids are to be used as highly attractive directing groups. Building upon previous studies in the group we aim to develop novel ligands and reaction conditions in order to achieve this goal. Overall, these studies are expected to deliver synthetically useful methods for the functionalization of complex organic molecules, which can contribute to addressing the abovementioned societal challenges.