Single asymmetric induction occurs when a chiral center or a chiral element in a molecule influences the stereochemical outcome of a reaction, leading to the formation of one dominant stereoisomer. The existing chirality biases the approach of reactants or the formation of intermediates, ensuring that a new stereocenter is formed with a predictable configuration.
A classic example of single asymmetric induction is the Sharpless epoxidation. In this reaction, a chiral allylic alcohol reacts with titanium tetra(isopropoxide) and diethyl tartrate in the presence of t-butyl hydroperoxide to form an epoxide. The chiral allylic alcohol dictates the stereochemistry of the epoxide formed, leading to a highly enantioselective product. The existing chirality in the allylic alcohol induces the formation of a specific epoxide enantiomer.