N,N′-Dicyclohexyl-N-(phthaloylglycyl)urea

The title urea derivative forms a one-dimensional supramolecular structure in the solid state, via intermolecular N—H⋯O hydrogen bonds.


Structure description
The crystal structure of N,N 0 -dicyclohexylurea (DCU) was first determined 50 years ago in space group P2/c (Coiro et al., 1971), followed by numerous redeterminations, including a wrong claim for a P1 polymorph (Zhu et al., 2009; the reported triclinic unit cell with Z 0 = 3 can be restored to the Laue 2/m class, using the transformation matrix [1 0 À1/3, 0 0 À1/3, 0 1 À1/3], affording the cell parameters of the actual P2/c structure with Z 0 = 1). This cheap compound is an entrance gate for many organic derivatives, through the functionalization of one or two of the amine groups (e.g. Orea Flores et al., 2006;Imhof, 2007;Pinheiro et al., 2012). While DCU has been found to be basic enough to coordinate to acid cations such as Nb 5+ or La 3+ (Aresta et al., 2010;Zhang et al., 2016), its derivatives obtained by functionalization of the amine groups cannot serve as ligands, because of the hindrance between urea substituents.
In the here-reported structure of the title compound, one amine, N12, is substituted by a phthaloylglycyl group (Fig. 1). Atom N12 is thus bonded to three bulky groups, and displays a planar geometry: the sum of angles at N12 is exactly 360 . The cyclohexyl groups have the normal chair conformation, and the phthaloyl plane is inclined by 46.53 (8) and 44.92 (7) with respect to the mean planes of the cyclohexyl rings. This conformation seems to be suitable for minimizing intramolecular steric hindrance.

data reports
The non-substituted DCU amine site, N14, is the single available donor group for hydrogen bonding. Weak N-HÁ Á ÁO hydrogen bonds are formed with the urea carbonyl group as acceptor (Table 1), forming chains of connected molecules in the crystal, parallel to [001]. Adjacent molecules within this supramolecular one-dimensional structure are related by the c glide planes of space group P2 1 /c, while the 2 1 screw axis relates parallel chains in the crystal (Fig. 2). A consequence of this arrangement is that the phthaloyl aromatic rings interact poorly in the crystal: the shortest distance between the centroids of symmetry-related benzene rings is 5.77 Å . The poor packing results in voids of ca 30 Å 3 , placed at the unitcell origin and at the centre of the (b, c) unit-cell faces. However, these voids seem to be empty, and attempts to model disordered solvent in the crystal did not improve the refinement. The poor crystal packing is reflected in the quite low Kitaigorodskii index of 0.643 (Kitaigorodskii, 1965;Spek, 2009).

Figure 1
Molecular structure of the title compound, with displacement ellipsoids at the 30% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

data-1
IUCrData ( Special details Refinement. The refinement was straightforward. All H atoms were placed in idealized positions, except amine H atom (H14), which was found in a difference map, and refined with free coordinates (Table 1).