Electrochemical Studies of Enantioselectivity at Chiral Metal Surfaces

Abstract

The combination of electrochemical methods with the use of well-defined kinked metal surfaces allows the experimentalist to examine many fundamental aspects of asymmetric reactions at solid surfaces in a new and detailed manner. For example, by systematically changing both the stereogenic center on a particular chemisorbing molecule and also the molecular architecture of the metal surface, relationships between adsorption geometry and reactive sites on the metal surface may be deduced. In addition, by measuring the differential rate of chemisorption of chiral auxiliaries on R and S metal surfaces insights in to the mechanism of the so-called “Orito” reaction (whereby enantioselective hydrogenation of α-ketoesters is observed) may be deduced. In the present article, a brief resumé of the relevant electrochemical and heterogeneous catalysis literature is expounded together with an analysis of the problem of chirality in two dimensions in order to show that, by utilizing an electrochemical surface science approach, the nature of asymmetric surface reactivity my be tackled in a systematic and accessible manner. Important questions regarding the surface stability or otherwise of chiral modifiers under reaction conditions may be addressed together with the relevance of surface structure in the chemisorption of such species. Some conclusions regarding the mechanism of the Orito reaction on the basis of new experimental data are discussed.