(Z)-2-Phenyl-3-pivaloyl-1,1-dipropylguanidine

In the title compound, C18H29N3O, a polysubstituted guanidine, the torsion angles indicate that the guanidine unit and the carbonyl group are almost perpendicular to one another [O—C—N—C= −7.40 (18), C—N—C—N= −97.21 (15) and 86.41 (13)°]. The crystal packing is stablized by intermolecular N—H⋯O hydrogen bonds, which link the molecules into a chain.


S1. Comment
The guanidinium moiety is present in diverse biologically active natural substances as well as in a number of medicinal compounds (Berlinck, 2002). Polysubstituted guanidines had received considerable interest as DNA binders (Ohara et al., 2007) and as anticancer agents (Ma et al., 2008;Brzozowski et al., 2007). In addition to their biological role, guanidine derivatives are widely utilized in synthetic organic chemistry, due to their high catalytic potential (Gomez et al., 2000;Kovacevic & Maksic, 2001). Due to their high proton affinity, guanidines can be considered as super-bases (Ishikawa & Isobe, 2002).
The title compound (Fig. 1) is a typical tetra-substituted guanidine with normal geometric parameters (Cunha et al., 2005;Murtaza et al., 2007Murtaza et al., , 2008Murtaza et al., , 2009 The crystal packing of the title compound shows intermolecular N-H···O hydrogen bonds, which link the molecules into a continuous chain (Fig. 2).

S2. Experimental
1-phenyl-3-(pivaloyl)thiourea (0.236 g, 1 mmol) [Rauf et al., 2009], dissolved in 10 ml of DMF, was placed in a two neck round bottom flask. Dipropylamine (0.14 g, 1 mmol) and triethylamine (0.28 ml, 2 mmol) were added and the mixture was stirred well at a temperature below 278 K. Mercuric chloride (0.272 g, 1 mmol) was then added and the mixture was stirred vigorously for 20 h. The progress of the reaction was monitored by TLC, untill the completion of reaction. When all the thiourea had been consumed, 20 ml of CH 2 Cl 2 was added and the suspension was filtered through a cintered glass funnel to remove residual HgS, formed as a byproduct during the reaction. The solvent was then evaporated under reduced pressure and the residue 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 the product was further purified by column chromatography. The target guanidine was recrystallized using ethanol.

S3. Refinement
The NH H-atom was located in a different electron-density map and freely refined: N-H = 0.837 (17)  where k = 1.2 for H-aromatic, and 1.5 for H-methyl.

Figure 1
Molecular structure of of the title compound, showing the atom numbering scheme and displacement ellipsoids drawn at the 50% probability level.  A view of the formation of the N-H···O intermolecular hydrogen bonded chain of molecules of the title compound (see Table 1 for details). 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 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.