A thermal rearrangement of ethylene acetal of bicyclo[4.2.0]octa‐4,7‐diene‐2,3‐dione

Pyrolysis of the title compound 3 at 400 °C gave α-(2-hydroxyphenyl)-γ-butyrolactone (4) whose structure was confirmed by an alternative synthesis. A reaction mechanism via a phenyl ketene acetal is proposed.