1-(2-Chloroethyl)-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one

In the title compound, C7H7ClN4O, the pyrazolopyrimidine ring is essentially planar, the r.m.s. deviation of the fitted atoms being 0.0071 Å. The crystal structure features strong N—H⋯O hydrogen bonds and further consolidated by weak C—H⋯O, C—H⋯N and C—H⋯Cl interactions.


Related literature
For the biological activity of pyrazolopyrimidines, see: Carraro et al. (2006). For a related structure, see: Dolzhenko et al. (2009). For the graph-set analysis of hydrogen bonding, see: Bernstein et al. (1995).
In the title compound ( Fig. 1), the fused pyrazolopyrimidine ring is substituted with 2-chloro-ethyl group on one side and the oxo group on the other side. The pyrazolopyrimidine ring is planar with the maximum deviation from the mean statistical plane being 0.0115 (14) Å for C3. The cis orientation of 2-chloro-ethyl group with respect to the C2-N2 bond is described by the torsion angle N2-C2-N3-C3, -2.204 (4)°.
The crystal structure is stabilized by some interesting features that comprise of intermolecular N-H···O, C-H···O, C -H···N and C-H···Cl interactions ( Fig. 2 and Tab. 1). The C-H···O and the N-H···O interactions result in centrosymmetric head-to-head dimers corresponding to the graph set R 2 2 (10) and R 2 2 (8) motif (Bernstein et al., 1995). There are two types of C-H···N interactions, one of which forms a helix, the other forms sheets along the crystallographic b-axis. The C-H···Cl intermolecular interaction result in one dimensional molecular chain along b-axis.
The bond lengths and bond angles in the title molecule agree very well with the corresponding bond distances and bond angles reported in a closely related compound (Dolzhenko et al., 2009).

Refinement
The H atoms were placed at calculated positions in the riding model approximation with N-H = 0.86 Å and C-H = 0.93, and 0.97 Å for aryl and methylene H-atoms respectively, with U iso (H) = 1.2U eq (N/C).

Computing details
Data collection: SMART (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 1998); data reduction: SAINT-Plus (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and CAMERON (Watkin et al., 1996); software used to prepare material for publication: WinGX (Farrugia, 1999).    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.19 e Å −3 Δρ min = −0.37 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.