3-(Adamantan-1-yl)-4-ethyl-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C14H21N3S, the 1,2,4-triazole ring is nearly planar, with a maximum deviation of 0.003 (4) Å. In the crystal, molecules are linked into inversion dimers by pairs of N—H⋯S hydrogen bonds.


Fun Comment
Derivatives of adamantane have long been known for their diverse biological activities including antiviral activity against the influenza (Vernier et al., 1969) and HIV viruses (El-Emam et al. 2004). Moreover, adamantane derivatives were recently reported to exhibit marked antibacterial activity (Kadi et al., 2007(Kadi et al., , 2010. In an earlier publication, we reported the synthesis and potent anti-inflammatory and analgesic activities of a series of 5-(1-adamantyl)-4-substituted-4H-1,2,4triazole-3-thiols and related derivatives including the title compound (El-Emam & Ibrahim, 1991).

Experimental
A mixture of adamantane-1-carbohydrazide (1.94 g, 0.01 mol), ethyl isothiocyanate (0.87 g, 0.01 mol), in ethanol (10 ml) was heated under reflux with stirring for one hour and the solvent was distilled off in vacuo. Aqueous sodium hydroxide solution (10%, 15 ml) was added to the residue and the mixture was heated under reflux for 2 h, then filtered hot. On cooling, the mixture was acidified with hydrochloric acid and the precipitated crude product was filtered, washed with water, dried and crystallized from aqueous ethanol to yield 2.24 g (85%) of the title compound (C 14

Refinement
Atom H1N2 was located in a difference Fourier map and refined freely [N-H = 0.87 (4) Å]. The remaining hydrogen atoms were positioned geometrically (C-H = 0.96-0.98 Å) and were refined using a riding model, with U iso (H) = 1.2 or 1.5U eq (C). A rotating group model was applied to the methyl group.

Figure 1
The molecular structure of the title compound, showing 30% probability displacement ellipsoids for non-H atoms.

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.