Crystal structure of 1-benzyl-4-formyl-1H-pyrrole-3-carboxamide

In the title compound, the mean planes of the pyrrole and benzyl rings are almost normal to one another with a dihedral angle of 87.07 (4)°. In the crystal, molecules are linked via a pair of N—H⋯O hydrogen bonds forming inversion dimers. C—H⋯O hydrogen bonds link the dimers into chains propagating along [10].


Chemical context
Pyrrole and its derivatives are classes of heterocyclic compounds and that have attracted much attention because of their potential pharmacological and biological properties (Davis et al., 2008;Meshram et al., 2010;Moriguchi et al., 2015). As a part of our work on the synthesis of new pyrrole derivatives with good biological activities, the title compound, (I), was synthesized and its crystal structure is reported on herein.

Structural commentary
The molecular structure of the title compound (I), is shown in Fig. 1. In the amide group, the C-N bond is relatively short [C12-N2 = 1.3374 (16) Å ], suggesting some degree of electronic delocalization in the molecule. The dihedral angle between the pyrrole and phenyl rings is 87.07 (4) , indicating that they are nearly perpendicular to each other. An intramolecular hydrogen bond, N2-H2BÁ Á ÁO2 (Table 1), encloses an S(7) ring motif.

Figure 2
A view of the inversion dimer formed by pairs of N-HÁ Á ÁO hydrogen bonds. Both the intramolecular and intermolecular hydrogen bonds are shown as dashed lines (see Table 1).

Figure 3
A view of the one-dimensional chain structure. The dashed lines indicate the N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds (see Table 1).

Figure 4
The view of the two-dimensional network structure. The C-HÁ Á Á interactions and the hydrogen bonds are shown with green and purple dashed lines, respectively (see Table 1). were found, see for example Bonnett et al. (1985); Choi et al. (1998); Sha et al. (1990); Wang et al. (2011). In these structures, the pyrrole and benzyl rings are also nearly perpendicular to one another.

Synthesis and crystallization
1-Benzyl-1H-pyrrole-3-carboxamide (1 mmol, 214.3 mg) was dissolved in methanol (20 ml) and irradiated with UV light at room temperature under oxygen (see Scheme). The reaction progress was monitored by thin layer chromatography (TLC). After completion, the solvent was removed under reduced pressure, and the residue was purified by chromatography on silica gel, using a mixed solvent of petroleum ether and ethyl acetate (10:1 ratio, v/v), to give the pure product. Colourless single crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of a methanol solution of the title compound at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were placed in idealized positions (C-H = 0.93-0.97 Å , N-H = 0.86 Å ) and refined as riding atoms, with U iso (H) = 1.2U eq (N,C).

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.