2-Benzoyl-1-(2,4-dichlorophenyl)-3-phenylguanidine

In the title compound, C20H15Cl2N3O, a typical polysubstituted guanidine with normal geometric parameters, the torsion angles [C—N—C—O = 3.8 (2), N—C—N—C = −6.1 (2)°] indicate that the guanidine and carbonyl groups are almost coplanar, due to the pseudo-hexagonal ring formed by intramolecular N—H⋯O hydrogen bonds. The crystal packing is stabilized by intermolecular N—H⋯O hydrogen bonds, which link the molecules into centrosymmetric dimers.

The authors are grateful to the Higher Education Commission of Pakistan for financial support of this research project.

Comment
Polysubstituted guanidines is a field of intense investigation as guanidinium group is present in diverse biologically active substances (Manimala & Anslyn, 2002;Berlinck, 2002) These compounds have received increasing interest as medicinal agents, e.g it has effect on the neuromuscular junction (Rodrigues-Simioni et al., 1997). In addition to their biological role, guanidine derivatives are very useful building blocks in synthetic organic chemistry (Costa et al., 1998;Kovacevic & Maksic, 2001). Due to their strongly basic character, guanidines can be considered as super-bases for the biological systems (Ishikawa & Isobe, 2002). The title compound (I), (Fig.1) is a typical N,N',N"-tri-substituted guanidine with normal geometric parameters (Cunha et al., 2005;Murtaza et al., 2007Murtaza et al., , 2008Murtaza et al., , 2009 (Table 1), forming a six-membered ring commonly observed in this class of compounds (Cunha et al., 2005). The crystal packing shows intermolecular N-H···O hydrogen bonds which link the molecules into centrosymmetric dimers (Fig. 2).
Experimental N-Benzoyl-N'-phenylthiourea (0.256 g, 1 mmol) was prepared  and dissolved in 10 ml of dimethylformamide and taken into two neck round bottom flask. 2,4-dichloroaniline (0.16 g, 1 mmol) and triethylamine (0.28 ml, 2 mmol) were added and the mixture was stirred well below 5°C. Mercuric chloride (0.272 g, 1 mmol) was then added and mixture was vigorously stirred for 15 h till the completion of reaction as monitored by TLC. When all the thiourea was consumed, 20 ml of chloroform was added and the suspension was filtered through sintered glass funnel to remove residual HgS formed as a byproduct during the reaction. The solvent was evaporated under reduced pressure and residue was dissolved in 20 ml of CH 2 Cl 2 . Other byproducts were extracted out with water (4×30 ml). The organic phase was dried over anhydrous MgSO 4 and then filtered. The solvent was evaporated and product was further purified by column chromatography. The target guanidine was recrystallized in ethanol to obtain single crystals suitable for X-ray analysis.

Refinement
Positional parameters of the H atoms bonded to N were refined with U iso (H) = 1.2U eq (N). Hydrogen atoms bonded to C were included in calculated positions and refined as riding on their parent C atom with C-H = 0.95 Å and U iso (H) = 1.2U eq (C).

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 > 2sigma(F 2 ) is used only for calculating R-factors(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.