Ethyl 10-cyano-7-hydroxy-6-oxo-3-phenyl-8,9,10,10a-tetrahydro-6H-benzo[c]chromene-10-carboxylate

The packing of the title compound is consolidated by C—H⋯O interactions.

In the title compound, C 23 H 19 NO 5 , the cyano group adopts an axial orientation and the ester group an equatorial orientation. The dihedral angle between the pendant phenyl group and the benzene ring of the fused-ring system is 25.97 (8) . Intramolecular O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds are observed and the packing is consolidated by C-HÁ Á ÁO and C-HÁ Á Á interactions.

Structure description
Dibenzopyran-6-ones (also called 6H-benzo[c]chromen-6-ones or 3,4,5,6-dibenzo-pyranones) form an important group of biologically active natural products that occur in bacteria, fungi, lichens, higher plants and animal waste (Bialonska et al., 2009). Elsamitrucin, a dibenzopyran-6-one derived drug, is an efficient topoisomerase II inhibitor (Fiocchi et al., 2011). As well as their biological activities, some dibenzopyran-6-ones have served as intermediates in the synthesis of more complex organic compounds (see, for example, Coghlan et al., 2001). As a part of our ongoing studies in this area, we now describe the synthesis and crystal structure of the title compound.
The title compound has a dibenzopyran moiety decorated by several substituents, as shown in Fig. 1. There are two stereogenic centres: in the arbitrarily chosen asymmetric molecule, C15 and C20 have S and R configurations, respectively, but crystal symmetry generates a racemic mixture. The nitrile group attached to C20 occupies an axial position and is anti to the hydrogen atom attached to C19. The dihedral angle between the pendant C1-C6 phenyl group and the C7-C12 benzene ring of the fused-ring system is 25.97 (8) . The Cremer-Pople puckering parameters of the O1/C9/C10/C13-C15 and data reports C14/C15/C17-C20 rings indicate half-chair conformations in each case with puckering amplitudes Q = 0.359 Å ; = 104.52 ; ' = 9.27 and Q = 0.49 Å ; = 134.17 ; ' = 327.35 , respectively. The O atom attached to C17 is stabilized in its enol (hydroxy) form, presumably as a result of forming a strong intramolecular hydrogen bond to O2. The packing is consolidated by weak C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions (Table 1) and an intramolecular C-HÁ Á ÁO interaction is also observed (Fig. 2).

Figure 2
Intermolecular interactions in the title compound.

Figure 1
The molecular structure of the title compound with the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level. Intramolecular hydrogen bonds are shown as dashed lines.
was cooled to room temperature, diluted with dichloromethane (DCM, 10 mL) and decanted. The residue was extracted with DCM (10 mL Â 2) twice. The solvent was removed from the combined DCM layers and the residue was subjected to column chromatography on silica gel (100-200 mesh) by using increasing amounts of ethyl acetate in hexane (5% to 15%) as eluent to afford the title compound as a lightyellow solid in 90% yield (84 mg); R f = 0.4 (hexanes:ethyl acetate, 7:3); m.p. 155-158 C. A sample suitable for singlecrystal X-ray analysis was obtained by recrystallization the 50 mg of the solid from a mixture of 1 mL of distilled chloroform and 0.5 mL of distilled methanol.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

data-1
IUCrData ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.010 Δρ max = 0.19 e Å −3 Δρ min = −0.20 e Å −3 Special details 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.

data-2
IUCrData (2022). 7, x220199 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 > 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. The hydrogen atoms in title compound were placed in calculated positions, with C-H = 0.93-0.97 A° and refined using a riding model with U iso (H) = 1.2 U eq (C) or 1.5U eq (C-methyl).