5,6-Dimethyl-4-(thiophen-2-yl)-1H-pyrazolo[3,4-b]pyridin-3-amine

In the title molecule, C12H12N4S, the thiophene ring is disordered over two orientations with a refined site-occupancy ratio of 0.777 (4):0.223 (4). The pyrazolopyridine ring system is essentially planar with an r.m.s. deviation of 0.0069 (3) Å and makes dihedral angles of 82.8 (2) and 72.6 (5)°, respectively, with the major and minor components of the thiophene ring. In the crystal, molecules are linked into a chain along the a axis by a pair of N—H⋯N(pyrazole) hydrogen bonds and a pair of N—H⋯N(pyridine) hydrogen bonds, both having a centrosymmetric R 2 2(8) graph-set motif. A C—H⋯π interaction is also present.

In the title molecule, C 12 H 12 N 4 S, the thiophene ring is disordered over two orientations with a refined site-occupancy ratio of 0.777 (4):0.223 (4). The pyrazolopyridine ring system is essentially planar with an r.m.s. deviation of 0.0069 (3) Å and makes dihedral angles of 82.8 (2) and 72.6 (5) , respectively, with the major and minor components of the thiophene ring. In the crystal, molecules are linked into a chain along the a axis by a pair of N-HÁ Á ÁN(pyrazole) hydrogen bonds and a pair of N-HÁ Á ÁN(pyridine) hydrogen bonds, both having a centrosymmetric R 2 2 (8) graph-set motif. A C-HÁ Á Á interaction is also present.

Related literature
For bond-length data, see: Allen et al. (1987). For details of hydrogen-bond motifs, see: Bernstein et al. (1995). For background to and bioactivity of pyrazole derivatives, see: Ali   Table 1 Hydrogen-bond geometry (Å , ).

Experimental
A mixture of 2-chloro-5,6-dimethyl-4-(thiophen-2-yl)nicotinonitrile (0.248 g, 1 mmol) and hydrazine hydrate (0.5 mL, 99%) in absolute ethanol (20 ml) was refluxed for 16 h. The reaction mixture was cooled and poured onto ice/water mixture. The precipitate that formed was filtered off, washed with water, dried and crystallized from EtOH/DMF to give yellow crystals of the title compound in 69% yield. Orange block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from ETOH/DMF (3:1 v/v) by the slow evaporation of the solvent at room temperature after several days.

Refinement
Amine H atoms were located from the difference map and refined isotropically. The remaining H atoms were placed in calculated positions with N-H = 0.86 Å , and C-H = 0.93 for aromatic and 0.96 Å for CH 3 groups. The U iso (H) values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The thiophene ring is disordered over two positions with the refined siteoccupancy ratio of 0.777 (4):0.223 (4). In the refinement, SAME and FLAT restraints were used for the minor component. The thermal ellipsoids of C9B and C10B were made to be the same.

Figure 1
The molecular structure of the title compound, showing 40% probability displacement ellipsoids and the atom-numbering scheme. Open bonds show the minor B component.    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.