Chirality via Cross-Coupling: New Asymmetric C-C Bond Formations Driven by Atom and Step Economy

Over 60% of the world’s top selling small molecule drug compounds are chiral and, of these, approximately 80% are marketed as single enantiomers. Surprisingly, and despite the tremendous advances made in catalysis over the past several decades, the average “chiral complexity” of drug discovery libraries has actually decreased, while, at the same time the “chiral complexity” of marketed drugs has increased. Consequently, there is now an urgent need to provide efficient processes that access directly privileged chiral “3D” building blocks. It is our philosophy that catalysis holds the key here and new processes should be based upon atom and step economical platforms that exert control over both absolute and relative stereochemistry. Palladium catalysed cross-coupling reactions of aryl (pseudo)halides with organo-nucleophiles (esp. the Suzuki coupling) have become mainstays of the pharmaceutical industry. Here, multiple “concession” steps are usually required to prepare the reaction partners, thereby detracting from atom and step economy. Further, these processes predominantly provide planar “2D” structures and are not well suited to the production of chiral “3D” building blocks. Consequently, methods that allow feedstock precursors (e.g. alkenes and aryl C-H bonds) to be combined directly in enantioselective or enantiospecific C-C bond formations are highly desirable. Cross-couplings of this type would circumvent “concession” steps, thereby minimising cost, effort and waste; however, such processes are highly challenging because of issues associated with regio- and stereocontrol. Recently, we developed prototype catalyst systems that can address this. In the proposed ERC project, these exciting preliminary results will be developed into a wider family of processes where asymmetric C-C bond formations are achieved directly by C-H activation. The new methods, which fulfil modern reaction ideals of atom and step economy, will likely find broad use in applied settings.