The chemistry of small‐ring compounds. Part 49. A route to oxaspiropentanes, undisturbed by rearrangement

The title compounds have been prepared in 70‐90% yield by epoxidation of appropriate cyclopropylidene compounds with KHSO5 in a phosphate buffer in the presence of acetone. The latter is converted into an unstable dioxirane, which acts as the oxygen‐transferring agent.