(±)-trans-5-Benzoyl-2-(1H-indol-3-yl)-4-phenyl-4,5-dihydrofuran-3-carbonitrile

The furan ring in the title compound, C26H18N2O2, is twisted about the C(H)—C(H) bond. The molecular structure is stabilized by an intramolecular C—H⋯O interaction, which generates an S(6) ring motif. The presence of N—H⋯N hydrogen bonds leads to inversion dimers, which are stabilized in the crystal packing by C—H⋯O and C—H⋯π interactions, forming layers that stack along the a axis.

The furan ring in the title compound, C 26 H 18 N 2 O 2 , is twisted about the C(H)-C(H) bond. The molecular structure is stabilized by an intramolecular C-HÁ Á ÁO interaction, which generates an S(6) ring motif. The presence of N-HÁ Á ÁN hydrogen bonds leads to inversion dimers, which are stabilized in the crystal packing by C-HÁ Á ÁO and C-HÁ Á Á interactions, forming layers that stack along the a axis.

Comment
Benzofurans have physiological, pharmacological and toxic properties, and there is continuing interest in their synthesis (Kappe et al., 1997). Various benzofuran derivatives have been investigated as estrogen receptor ligands, because selective estrogen receptor modulators such as ralixofene have emerged as potential therapeutics for the prevention and treatment of osteoporosis (Sato et al., 1999;Smith et al., 2002). In view of their high medicinal value, and in conjunction with our research interests, we were prompted to synthesize and report the X-ray structure determination of the title compound, (I).
The presence of N-H···N hydrogen bonds leads to inversion dimers which are stabilised in the crystal packing by C-H···O and C-H···π interactions, Table 1, to form layers that stack along the a axis, Fig. 2.

Experimental
To a stirred mixture of 2-(1H-indole-3-carbonyl)-3-phenylacrylonitrile (1.0 eq.) and phenacylpyridinium bromide (1.0 eq.) in water (10 ml) was added drop-wise triethylamine (0.25 eq.) at room temperature. The resulting clear solution, that slowly became turbid, was stirred at room temperature for 0.5 h. Then the separated free-flowing solid was filtered and washed with methanol (3 ml) to afford the title compound as pale-yellow solids. The product was recrystallized from EtOH/EtOAc mixture (1:1 ratio v/v ml) to give pure compound, as pale-yellow crystals. M. pt: 521 K; Yield: 88%.

Refinement
H atoms were placed at calculated positions and allowed to ride on their carrier atoms with N-H = 0.86 Å and C-H = 0.93-0.98 Å, and with U iso = 1.2U eq (N,C) for CH and U iso = 1.5U eq (C) for CH 3 .  The molecular structure of (I), showing 30% probability displacement ellipsoids and the atom-numbering scheme.

Figure 2
The packing diagram of the molecule (I). The C-H···O interactions are shown as dashed lines.  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.