Oxidation of cyclopropanone hydrate and hemiacetal by metal ions: (Preliminary communication)

The isomerisation of cyclopropanone hemiacetal to propionic ester can be suppressed by metal ions such as Ag + and Cu 2+ . These mild oxidising agents can lead to adipic ester (up to 80%) through dimerisation of a radical CH 2 CH 2 COOR (III) detectable by ESR. This radical is not formed via propionic ester, but by isomerisation of a cyclic radical II, the primary oxidation product of the hemiacetal. With ferric chloride the radical can pick up chlorine to form β‐chloropropionic ester. The reactions are equally facile with cyclopropanone hydrate leading to adipic acid and β‐chloropropionic acid.