5-(Thiophen-2-ylmethyl)-1,3,4-thiadiazol-2-amine

In the title molecule, C7H7N3S2, the dihedral angle between the thiophene and thiadiazole rings is 72.99 (5)°; the two rings are oriented so that the S atoms in each ring are on the same side. In the crystal, the three-dimensional network involves strong N—H⋯O hydrogen bonds, as well as C—H⋯π and π–π stacking interactions [centroid–centroid distances = 3.654 (1) and 3.495 (1) Å].

In the title molecule, C 7 H 7 N 3 S 2 , the dihedral angle between the thiophene and thiadiazole rings is 72.99 (5) ; the two rings are oriented so that the S atoms in each ring are on the same side. In the crystal, the three-dimensional network involves strong N-HÁ Á ÁO hydrogen bonds, as well as C-HÁ Á Á and stacking interactions [centroid-centroid distances = 3.654 (1) and 3.495 (1) Å ].

D-HÁ
Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.  (Olesan et al., 1955). 2-Amino-1,3,4-thiadiazole (ATDA), as the most promising compound, was used in phase II clinical trials in patients with different tumors: renal, colon, ovarian, and others. Recently new derivatives with the 1,3,4-thiadiazole nucleus as well as Fe(II) / Fe (III) complexes of 2amino-1,3,4-thiadiazoles have been synthesized and evaluated for their antiproliferative activity against a panel of human cancer cell lines (Mishra et al., 1995). Over recent years, there has been an increasing interest in the chemistry of thiophenes because of their biological significance. Many of them have been widely investigated for therapeutic uses, especially as antifungal, antibacterial, anti-inflammatory, anticonvulsant, antiasthmatic, and analgesic agents. They also were known to show anti-HIV, antiproliferative, germicidal, and D2 dopaminergic activities (Mohareb et al., 2004). In view of these facts, the aim of this present study is to obtain a structure of 1,3,4-oxadiazole incorporating the thiophene ring.
In the molecule of the title compound (Fig 1), the bond lengths are within normal ranges (Allen et al., 1987). In the molecule of (I) atom S1 is oriented towards the thiadiazol ring, Fig. 1. The dihedral angle between the planar thiophene (r.m.s. deviation = 0.007 Å) and planar thiadiazol (r.m.s. deviation = 0.004 Å) rings of 72.99 (5)° indicates a twist between planes as seen in the S1-C4-C5-C6 torsion angle of 94.86 (17) °. The amine group is effectively co-planar with the thiadiazol ring to which it is attached as seen in the N3-C7-S2-C6 torsion angle of 178.53 (16) °.

Experimental
The title compound was synthesized using the published method (Sancak et al., 2007).

Refinement
The amine H atoms were seen in a difference Fourier map and then idealized with U iso (H) = 1.2U eq (N) with N-H bond length of 0.86 Å. The C-bound H-atoms were positioned geometrically with C-H = 0.93 and 0.97 Å, for aromatic and CH 2 H-atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). During the refinement it was noticed that for the strongest reflections (F c /F c (max) close to 1.00) the observed value (F o ) was much smaller than the calculated value (F c ) indicating detector saturation problems. These reflections were omitted from the refinement.

Figure 1
View of the molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level for non-hydrogen atoms.

Figure 2
The packing view showing the hydrogen bonds network. Dashed lines indicate intermolecular N-H···N hydrogen bonds (see Table 1 for details).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.