(E)-2-(2-Nitroethenyl)furan

The title compound, C6H5NO3, was synthesized via condensation of furfural with nitromethane in the presence of isobutylamine. The compound crystallizes exclusively as the E isomer. The angle between the mean planes of the furan ring and the nitroalkenyl group is 1.3 (2)°.

We thank the SCCYT (Universidad de Cá diz) for the X-ray data collection and the Consejería de Innovació n, Ciencia y Empresa de la Junta de Andalucía, for financial support. ZRN thanks the AUIP and Aula Iberoamericana for the stay at UCA.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FJ2237).
on the structures of the more simple compounds in this family. We start with this study a series of structural reports about them. The structure of title compound, showing trans or E configuration, is shown in Fig. 1. Ring aromaticity is extended to the alkenyl group being C1-C5 bond length, 1.430 (2), significatively shorter than a single C-C bond. Alkenyl sp 2 carbons mantain coplanarity with furan ring as shown by an angle of 1.3 (2)° between ring plane and C5-C6-N1 plane.

Crystal packing does not show hydrogen bonds nor N···π intermolecular interactions (Fig. 2).
Experimental 2-(2-Nitro-ethenyl)-furan, also called G-0, was obtained by a variation of Knoevenagel's method: condensation of an aldehyde with substances containing an active α-hydrogen in the presence of a base (ammonia or amines) as catalyst. The Centro de Bioactivos Químicos (Cuba) has already patented this modified method using furfural, an aromatic compound from acid hydrolisis of sugar cane residuals (straw, sawdust, etc.) and nitromethane in the presence of isobutylamine. A yellow crystalline solid was obtained with purity higher than 98%, melting point 74.5°, scarcely soluble in water and very soluble in nitromethane, carbon tetrachloride, petroleum ether and ethanol.

Refinement
All H atoms were positioned geometrically and treated as riding (C-H = 0.99Å for methylene and C-H = 0.93Å otherwise).
U iso (H) = 1.2 U eq (C) of the carrier atom.

Special details
Experimental. Refinement of F 2 against unique set of 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.
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 unique set of 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.