Chirality at Surfaces: Applications in Heterogeneous Catalysis

Chirality plays a vital role in our day-to-day lives; from the way food tastes and smells to the delicate interactions that help to treat all manner of diseases and ailments using pharmaceuticals. The worldwide market for single enantiomer pharmaceuticals is currently in excess of $200 billion and is rapidly rising. Current manufacturing techniques for the required enantiopure drugs are often slow, costly and wasteful. Many involve post-synthesis separation of the desired enantiomer from the reaction mixture. Any unwanted products are either discarded, with associated environmental impact, or reprocessed at additional cost. Enantioselective heterogeneous catalysis offers a direct synthetic route to chemicals of high optical purity. As with many heterogeneous catalytic systems, they often exhibit the additional benefit of being significantly more atom-efficient than comparable homogeneous routes, i.e. they do not require expensive and hard to handle “single-atom” donors. In this talk I will briefly highlight three successful examples of enantioselective heterogeneous catalysis that employ additional chiral modifiers or auxiliaries to impart chirality into an otherwise racemic system. They show how single-crystal based model systems studied under ultra high vacuum conditions may be used to modify and direct the reactions occurring at atmospheric and higher pressures using high surface area supported catalysts. The systems I will discuss show how both the chemical nature of the chiral modifier and reactant molecules and their molecular orientations and interactions at the catalyst surface greatly affect the reaction outcome