1,3-Dicyclohexyl-1-(4-nitrobenzoyl)urea

In the title compound, C20H27N3O4, both cyclohexane rings adopt chair conformations. The benzene ring and the amide group are oriented at a dihedral angle of 62.1 (2)°. In the crystal structure, intermolecular N—H⋯O and C—H⋯O hydrogen bonds link the molecules into chains propagating in [010], which contain R 2 2(12) ring motifs.


Comment
Benzoylurea derivatives act as antimitotic (Song et al., 2008) and antiproliferative (Song et al., 2009) agents. Some of the N-aroylurea analogs have been found to exhibit antioxidant activity (Amornraksa et al., 2009). We report here the crystal structure of the title compound, (I), an aroylurea.
Experimental 4-Nitrobenzoic acid (1 g, 5.9 mmol) and dicyclohexylcarbodiimide (1.203 g, 5.9 mmol) were dissolved in dichloromethane (30 ml). The resulting mixture was stirred overnight and then the solvent was removed by rotary evaporator. The product was isolated by column chromatography by using ethyl acetate-hexane (1:9) as eluent. Pale yellow blocks of (I) were obtained by slow evaporation of an ethanolic solution over a period of two weeks.

Refinement
H atoms were initially located in a difference Fourier map and later placed in idealized positions and constrained to ride on their parent atoms, with N-H = 0.86 Å, C-H = 0.93-0.98 Å and U iso (H) = 1.2U eq (C,N). The U ij parameters of the nitro group atoms indicate possible disorder but attempts to model the disorder were not successful. Beamstop affected reflection 200 was omitted during the refinement. Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.