(E)-2-(2-Furylmethylidene)-2,3-dihydro-1H-pyrrolizin-1-one

The title compound, C12H9NO2, was prepared by an Aldol reaction of furfuraldehyde with 2,3-dihydro-1H-pyrrolizin-1-one. The molecule is almost planar, with an r.m.s. deviation of 0.045 Å, excluding the methylene H atoms. In the crystal structure, molecules are linked via weak intermolecular C—H⋯O hydrogen bonding and aromatic π–π stacking [centroid–centroid distance = 3.6151 (9) Å].


Comment
Derivatives of 2,3-dihydropyrrolizine became known through studies of their synthesis (Clemo & Ramage, 1931;Braunholtz et al., 1962) and isolation from natural source (Meinwald & Meinwald, 1965). Synthetic dihydropyrrolizines that are of interest as pharmaceuticals have been reported. The most important of these, Ketorolac, is a non steroid analgesic. Depending on their structure, derivatives of 2,3-dihydropyrrolizine have shown merit as analgesics, anti-inflammatory agents, myorelaxants, inhibitors of thrombocyte aggregation, fibrinolytics, temperature-lowering substances and drugs for the treatment of glaucoma and conjunctivitis (Skvortsov & Astakhova, 1992).
Numbering scheme for the title compound is shown in an ORTEP (Farrugia, 1997) plot of the molecule, see Fig. 1. The three rings are essentially planar, rms deviation = 0.045 Å, with two metnylene H atoms above and below the plane ( Fig.   2). Weak intermolecular C-H···O hydrogen bonding (Table 1) and aromatic π-π stacking between O2-containg ring and N1-containg ring [the centroids distance 3.6151 (9) Å] are present in the crystal structure (Fig. 3). Double bond connecting two ring systems have an E configuration.

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H = 0.95 and 0.99 Å for aromatic and methylene respectively. U iso (H) values were taken to be equal to 1.2 U eq (C) for all hydrogen atoms.

Special details
Experimental. Single crystals suitable for X-ray crystallography were grown by slow evaporatin from ethyl acetate solution and of by slow cooling of a hot saturated solution of Petroleum Ether. Crystals obtained from later were found more suitable for X ray analysis.
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 > σ(F 2 ) is used only for calculating Rfactors(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.