Ethyl 3′-(2,4-dichlorophenyl)-5′-hydroxy-5′-methyl-4′,5′-dihydrospiro[fluorene-9,2′(3′H)-furan]-4′-carboxylate

The furan ring and the five-membered fluorene unit in the title compound, C26H22Cl2O4, adopt envelope conformations. Intermolecular C—H⋯O interactions between symmetry-related molecules involving two C—H groups and an O atom as a bifurcated acceptor generate centrosymmetric hydrogen-bonded dimers with cyclic R 2 2(16) and R 2 2(8) ring motifs. A short C—H⋯Cl intramolecular contact occurs in the molecule.

The furan ring and the five-membered fluorene unit in the title compound, C 26 H 22 Cl 2 O 4 , adopt envelope conformations. Intermolecular C-HÁ Á ÁO interactions between symmetryrelated molecules involving two C-H groups and an O atom as a bifurcated acceptor generate centrosymmetric hydrogenbonded dimers with cyclic R 2 2 (16) and R 2 2 (8) ring motifs. A short C-HÁ Á ÁCl intramolecular contact occurs in the molecule.

Related literature
For spiro compounds in pharmacologically active alkaloids, see: Cravotto et al. (2001). For the anticonvulsant activity of fluorene derivatives, see: Vanvakides et al. (2004). Fluorene derivatives, including polyfluorenes and oligofluorenes, are promising candidates for blue light-emitting materials in organic light-emitting devices (Muller et al., 2003), organic phototransistors (Saragi et al., 2004), non-linear optics (Kim et al., 1998) and photochromic materials (Chun et al., 2003). For the biological activity of furan derivatives and annulated furan derivatives and their use as precursors for the synthesis of natural products, see: Greve & Friedrichsen (2000). For hydrogen-bond motifs and ring puckering parameters, see: Bernstein et al. (1995); Cremer & Pople (1975);Nardelli (1983). For a related spiro-linked system, see: Feng et al.  Table 1 Hydrogen-bond geometry (Å , ).   (Vanvakides et al., 2004). In addition, fluorene derivatives, including polyfluorenes and oligofluorenes, have been studied extensively in recent years because they are very promising candidates for blue light-emitting materials in organic light-emitting devices (Muller et al., 2003), organic phototransistors (Saragi et al., 2004), nonlinear optics (Kim et al., 1998) and photochromic materials (Chun et al., 2003). Furan derivatives and annulated furan derivatives occur widely in nature and, along with their unnatural analogs, have been shown to have a wide range of biological activity as well as being important precursors for the synthesis of natural products (Greve & Friedrichsen, 2000). In view of these important properties, the crystal structure of the title compound, (I), has been determined.
in (I, Fig. 1) the C4-C5 and C4-C16 bond distances of the fluorene moiety are almost identical to the values reported in another spiro-linked system (Feng et al., 2004).
The benzene ring is planar with the largest displacement observed being -0.014 (1) Å for atom C22. The deviations of the atoms Cl1 and Cl2 from the least-squares plane of the phenyl rings are -0.114 (1) and 0.015 (1) Å, respectively.

Experimental
To a stirred mixture of 9-(2,4-Dichloro-benzylidene)-9H-fluorene (1.0 mmol), ethylacetoacetate (1.0 mmol) and NaHCO 3 (3.0 mmol) in acetonitrile (10 ml), ceric ammonium nitrate (2.5 mmol) dissolved in acetonitrile (5 ml) was added dropwise at 0 ° under N 2 . The reaction mixture was stirred until completion of the reaction as monitored by TLC. Water was added to the mixture and the product was extracted with ethyl acetate (2 × 20 ml) and then dried over anhydrous Na 2 SO 4 . Removal of the solvent under reduced pressure gave a crude product, which was purified by column chromatography on silica gel, supplementary materials sup-2 with ethyl acetate-hexane (4:6) as eluent to afford a pure product in 79% yield. Single crystals of the title compound suitable for X-ray diffraction were obtained by slow evaporation of a solution in ethylacetate.

Refinement
All H atoms were positioned geometrically, with O-H = 0.82 and C-H = 0.93-0.98 Å and constrained to ride on their parent atoms, with U iso (H) = xU eq (C, N), where x = 1.5 for methyl H and x = 1.2 for all H atoms. Fig. 1. The molecular structure of (I), showing the atom-numbering scheme for. Displacement ellipsoids are drawn at the 50% probability level.  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.