3′‐Iso­propyl‐8′,8′‐di­methyl‐2‐benzofuran‐1‐spiro‐7′‐bi­cyclo­[4.2.0]­octa‐1′(6′),2′,4′‐trien‐3‐one

Photolysis of a 2-(2-isopropyl-benzoyl) benzoate ester derivative in an oxygen-free environment results in the liberation of the alcohol from the ester and formation of the title spirolactone, C20H20O2. The molecule of the title compound adopts the syn configuration with respect to the benzene rings, with a dihedral angle of 87.19 ( 5) degrees between the benzocyclobutene and isobenzofuranone ring planes. The cyclobutene ring is nearly planar, giving rise to ring distortion, as manifested in the bond distances and angles.