Crystal structure of 1-ethyl­spiro­[imid­az­olidine-4,1′-indane]-2,5-dione

In the title compound, C₁₃H₁₄N₂O₂, the C₅ ring has an envelope conformation with the C atom adjacent to the quaternary C being the flap. The five atoms comprising the imidazolidine-2,4-dione ring are almost planar (r.m.s. deviation = 0.004 Å). The dihedral angle between the five-membered rings is 89.66 (10)°. In the crystal, inversion-related mol­ecules are connected via {...HNCO}₂ synthons. These are linked into a helical supra­molecular chain along [010] by C—H...O inter­actions.