Recent Advances in Iminium-Salt-Catalysed Asymmetric Epoxidation

Epoxides are important functional groups that are present in bioactive natural products and serve as useful building blocks for the formation of more complex molecular architectures. While asymmetric epoxidation methods have been known for four decades, in recent years there has been a drive to carry out transformations using organocatalysts. In this review we will discuss the application of iminium salts as organocatalysts in asymmetric epoxidation reactions, which has received a lot of attention over the last decade. We pay particular attention to the use of dihydroisoquinolinium salts and iminium salts based on binaphthyl and biphenyl systems in the asymmetric epoxidation of a broad range of olefin substrates.