Epoxidation of Enol Silyl Ethers, Phosphates, Esters, and Lactones by Dimethyldioxirane

The epoxides 2a–u (Table 1) of the enol silyl ethers 1a, b, enol phosphates 1c–k, and enol esters and lactones 11–u were prepared in excellent yields by epoxidation with isolated dimethyldioxirane (4) (as acetone solution). These labile epoxides (stable below 0°C) could be isolated in pure form and characterized spectroscopically (IR, 1H and 13C NMR). The derivatives 2p–u were sufficiently stable so that even C,H analyses were obtained. Warming up to room temperature led to rearrangement to the corresponding α‐oxy‐functionalized carbonyl products 3. Since epoxide 2c was sufficiently resistant towards hydrolysis, it could be prepared by the in situ method.