Transition Metal-Catalyzed Coupling Reactions in Library Synthesis

Abstract

It has been widely recognized that the global pharmaceutical and agrochemical industries are currently experiencing a dynamic change. To increase productivity and efficiency, agro and drug companies have been striving to make improvements in every aspect of the R&D. Consequently, new technologies providing novel chemical cores currently are of great demand at all major companies.Furthermore, high-throughput screening requires the synthesis of larger and more diverse sets of compounds. High-throughput synthesis of heterocyclic compound libraries utilizes various combinatorial strategies including direct scaffold decoration, linear convergent, and divergent approaches.Biphenyl frameworks (including heteroaromatic moieties) are found in many biologically active products and thus can be considered as a privileged motif in medicinal chemistry.The emergence of transition metal-catalyzed coupling reactions readily facilitated library/scaffold diversification with the easy incorporation of aromatic/heteroaromatic rings into various chemotypes that are preferentially directed towards hydrophobic cavities of protein targets. Typically, carbon–halogen bonds are utilized for a variety of transition metal (mostly palladium)-catalyzed reactions, including Suzuki–Miyaura, Sonogashira, Buchwald–Hartwig, Stille, Negishi, and Heck couplings. Most recently, direct C–H activation/arylation protocols were also reported for direct derivatization of heterocyclic cores.On the other hand, cross-coupling reactions were also implemented into domino and cascade reactions to enable multiple bond-forming and bond-cleaving events in a single synthetic operation yielding efficiently novel ring systems.KeywordsCatalysisCross-couplingLibrary synthesisPalladium metal