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 1l-u were prepared in excellent yields by epoxidation with isolated dimethyldioxirane (4) (as acetone solution). These labile epoxides (stable below 0-degrees-C) could be isolated in pure form and characterized spectroscopically (IR, H-1 and C-13 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 alpha-oxy-functionalized carbonyl products 3. Since epoxide 2c was sufficiently resistant towards hydrolysis, it could be prepared by the in situ method.