On cyclopentadienone-ketals and their dimers. A novel rearrangement of α,β-unsaturated ketone dialkyl ketals

The dimers $\text{2a}$ & b) of dimethyl- and diethylcyclopentadienone ketals($\text{1a}$ & b) undergo a novel 1,3-alkoxy-rearrangement to $\text{4}$(a & b). Mild hydrolysis of $\text{2}$ or $\text{3}$ gives the monoketones ($\text{3}$a or b). On strong acid catalysed hydrolysis $\text{2}$, $\text{3}$ or $\text{4}$ afford the cyclopentadienone-dimer($\text{6}$.