Oxidation of 1-methylcyclobutene by metal ions

Metal ions such as thallium(III), mercury(II), and palladium(II) oxidize 1-methylcyclobutene in aqueous solution to cyclopropyl methyl ketone; these reactions, as well as the silver(I)- and palladium(II)-catalysed rearrangements of cubane and related compounds, are interpreted in terms of carbonium-ion mechanisms.