Crystal structure of (5-methylimidazo[1,2-a]pyridin-2-yl)methanol

In the title compound, C9H10N2O, the imidazo[1,2-a]pyridine moiety is approximately planar (r.m.s. deviation = 0.024 Å). The methanol group is nearly perpendicular to its mean plane as indicated by the C—C—C—O and N—C—C—O torsion angles of 80.04 (16) and −96.30 (17)°, respectively. In the crystal, molecules are linked by O—H⋯N hydrogen bonds, forming inversion dimers with an R 2 2(10) ring motif. The dimers are liked via C—H⋯O hydrogen bonds, enclosing R 2 2(10) ring motifs and forming ribbons along [201]. The ribbons are linked via a number of π–π interactions [centroid–centroid distances vary from 3.4819 (8) to 3.7212 (8) Å], forming a three-dimensional structure.


S1. Comment
Imidazo[1,2-a]pyridine moieties represent important building blocks in both natural and synthetic bioactive compounds, which have been shown to possess diverse therapeutic activities (Silvestre et al., 1998;Hamdouchi et al., 1999;Lhassani et al., 1999;Ertl et al., 2000). The synthesis of the title compound is based on the methods described in the literature (Ohler et al., 1983;Chavignon et al., 1992).
The title compound is formed by a fused five-and six-membered rings almost coplanar, with a maximum deviation of 0.029 (1) Å for C7 atom (Fig. 1). The mean plane through the fused ring system (N1/N2/C1-C7) is nearly perpendicular to the hydroxide group as indicated by the torsion angle C6-C7-C8-O1 of -96.30 (17) °.
The cohesion of the crystal structure is ensured by C6-H6···O1 and O1-H1···N1 hydrogen bonds, forming ribbons lying nearly perpendicular to the a axis, as shown in Fig. 2 and Table 1. There are a number of π-π interactions present linking the ribbons and forming a three-dimensional structure [Cg1···Cg1 i = 3.6025 (7)

S2. Experimental
The process for the synthesis of (5-methyl-imidazo[1,2-a]pyridine-2-yl) methanol described here occurs in two distinct stages: 1) Condensation of the 6-methylpyridin-2-amine with the ethyl bromopyruvate in boiling methanol. The mixture was then heated at 343 K for 4 h and neutralized at 273 K with Na 2 CO 3 . The product was extracted with dichloromethane. The organic layer was dried over sodium sulfate and the dichloromethane removed under reduced pressure. The crude product was purified on a silica gel column and identified as ethyl-5-methylimidazo [1,2-a]pyridine -2-carboxylate with 60% yield; 2) The reduction of the ester prepared above with lithium hydride and aluminium at room temperature in methanol for 2 h leads to a solid phase which was recrystallized from ethanol. Colourless crystals of the title compound were obtained with a yield of 67% (m.p. 413 K).  A view of the molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A partial view perpendicular to a axis of the crystal packing of the title compound, showing a layer of molecules linked by hydrogen bonds (dashed lines; see Table 1 for details).  (14) 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.