Buy article online - an online subscription or single-article purchase is required to access this article.
organic compounds
The title compound, C21H22N2O2, was synthesized from the corresponding pyrazolidinedione precursor by 9-fluorenyl substitution and subsequent ring expansion. The hexahydropyrimidinedione (HHPD) ring has a very flattened chair conformation and is nearly perpendicular [88.79 (13)°] to the 2-spiro-9′-fluorene ring. The two ethyl groups adopt a folded conformation and lie on opposite sides of the HHPD ring. A hydrogen-bonding scheme consisting of N—HO=C and C—HO=C interactions produces parallel molecular layers.