Reaction of ethyl 2,2-dimethoxycyclopropanecarboxylates with m-CPBA. Discovery of two new related degradative processes leading to β-hydroxyacid derivatives

The reaction of the 3-alkyl-substituted and 3,3-dialkyl-substituted ethyl 2,2-dimethoxycyclopropanecarboxylates 1–3 with m-CPBA in CH2Cl2 leads to the formation of the β-hydroxyacid derivatives 4–6 via two related processes involving the scission of both the C1C2 and C2C3 bonds and consequently to the degradation of the original cyclopropane carbon skeleton (extrusion of the C-2 carbon). Cis- and trans-2-ethoxycyclopropanecarboxylic acid ethyl esters 9 and 10, respectively, structurally related to 1–3, are unreactive under the same conditions. A hypothesis explaining the observed reactivity is formulated.