Highly beta-selective epoxidation of delta5-unsaturated steroids catalyzed by ketones

A general catalytic and environmentally friendly method for beta-epoxidation of delta5-unsaturated steroids has been developed, which uses ketones as the catalysts and Oxone as the terminal oxidant. A whole range of delta5-unsaturated steroids, which bear different functional groups such as hydroxyl, carbonyl, acetyl, or ketal, as well as different side chains, were conveniently converted to the corresponding synthetically and biologically interesting 5beta,5beta-epoxides with excellent beta-selectivities and high yields.