Ethyl 5-bromonaphtho[2,1-b]furan-2-carboxylate

In the title compound, C15H11BrO3, the dihedral angle between the naphthofuran ring system (r.m.s. deviation = 0.022 Å) and the side chain is 4.50 (2)°. In the crystal, short Br⋯Br [3.4435 (7) Å] contacts propagating along [010] in a zigzag manner and weak π–π interactions [shortest centroid–centroid separation = 3.573 (2) Å] directedalong [100] are observed.

BSPM thanks Dr H. C. Devarajegowda, Department of Physics, Yuvarajas College (constituent), University of Mysore and T. Srinivasan, Centre of Advanced Study in Crystallography and Biophysics, University of Madras Guindy Campus, Chennai for their support.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB7019).
The title compound crystallizes in monoclinic crystal system with P2 1 /c space group. The molecule is essentially planar with the dihedral angle between the mean planes defined by the naphthofuran moiety and the side chain is 4.50 (2)°, and the torsion angle of 179.81 (2) o for C15-C14-O3-C13 shows that the ethyl group is in planar orientation with the naphthofuran ring. In contrast to this, an antiperiplanar orientation is observed between the ethyl group and the naphthofuran ring in ethylnaphtho[2,1-b]furan-2-carboxylate. In the crystal, weak Br···Br and π-π interaction between the rings C1-C6 and O1-C12 occur.

Experimental
To a solution of ethyl naphtho[2,1-b]furan-2-carboxylate (0.1 mol) in glacial acetic acid (20 ml) was added a solution of bromine (0.1 mol) in acetic acid (20 ml) with stirring during 1 h at 10-20°C and the stirring was continued for 3 h. The reaction mixture was poured into ice-cold water and the solid obtained was filtered out. It was washed with water, dried and the product was recrystallized from ethanol solution as colourless prisms.

Refinement
The H atoms were positioned with idealized geometry using a riding model with C-H = 0.93 -0.97 Å. The isotropic displacement parameters for all H atoms were set to 1.2 times of the U eq of the parent atom (1.5 times of the U eq of the parent atom for CH3).

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.