N-tert-Butyl-2-[4-(dimethylamino)phenyl]imidazo[1,2-a]pyrazin-3-amine

In the title compound, C18H23N5, the imidazole ring makes a dihedral angles of 3.96 (8) and 19.02 (8)°, respectively, with the pyrazine and benzene rings while the dihedral angle between the pyrazine and benzene rings is 16.96 (7)°. In the crystal, molecules are linked via N—H⋯N hydrogen bonds, forming chains along [010]. These chains are linked by C—H⋯N hydrogen bonds, forming two-dimensional networks lying parallel to (001).

In the title compound, C 18 H 23 N 5 , the imidazole ring makes a dihedral angles of 3.96 (8) and 19.02 (8) , respectively, with the pyrazine and benzene rings while the dihedral angle between the pyrazine and benzene rings is 16.96 (7) . In the crystal, molecules are linked via N-HÁ Á ÁN hydrogen bonds, forming chains along [010]. These chains are linked by C-HÁ Á ÁN hydrogen bonds, forming two-dimensional networks lying parallel to (001).
In the crystal, molecules are linked via N-H···N hydrogen bonds forming chains along [010]. These chains are linked by C-H···N hydrogen bonds forming two-dimensional networks lying parallel to (001); see Table 1 and Fig. 2 for details.

Experimental
2-aminoamidine (1.0 mmol) was placed in an oven-dried round bottom flask, dissolved in EtOH (5.0 mL) and stirred at room temperature. 4-N,N-dimethyl benzaldehyde (1.0 mmol), isocyanide (1.0 mmol) and Iodine (2.0 mol%) were added sequentially and the mixture stirred at room temperature for one hour. Progress of the reaction was monitored by TLC.
When finished the reaction mixture was concentrated under reduced pressure and the crude product was partitioned between EtOAc and water. The organic phase was separated, and the residual product in the aqueous phase was extracted with EtOAc (2 × 10 mL). The combined organic extract was dried over anhydrous Na 2 SO 4 , filtered, concentrated and purified using column chromatography (silica gel 60-120 mesh, elutent: 2% EtOAc in hexane). Colourless block-like crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of a solution of the title compound in ethanol at room temperature [M.p: 478 -480 K; IR (KBr, cm -1 ): 3259 (NH)]

Refinement
The NH H atom was located in a difference Fourier map and freely refined. The C-bound H atoms were placed in calculated positions and refined in the riding model: C-H = 0.93 -1.08 Å with U iso (H) = 1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms. program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008)and PLATON (Spek, 2009).

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.  The crystal packing of the title compound viewed along the c axis. The hydrogen bonds are shown as dashed lines [see Table 1 for details; H-atoms not involved in hydrogen bonds have been omitted for clarity].

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.