(6bS*,14R*,14aR*)-Methyl 14-(4-methylphenyl)-7-oxo-6b,6c,7,12b,14,14a-hexahydro-1H-pyrano[3,2-c:5,4-c′]dichromene-14a-carboxylate

In the title compound, C28H22O6, the chromeno ring system is almost planar, with a dihedral angle between the mean planes of the pyran and benzene rings of 1.87 (8)°. The pyran ring bearing the methylphenyl substituent has a half-chair conformation while the other pyran ring has an envelope conformation with the tetrasubstituted C atom as the flap. The benzene ring of the chromeno ring system is inclined to the benzene ring fused to the latter pyran ring by 74.66 (9)°. These aromatic rings are inclined to the 4-methylphenyl ring by 52.67 (9) and 66.63 (10)°, respectively. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

In the title compound, C 28 H 22 O 6 , the chromeno ring system is almost planar, with a dihedral angle between the mean planes of the pyran and benzene rings of 1.87 (8) . The pyran ring bearing the methylphenyl substituent has a half-chair conformation while the other pyran ring has an envelope conformation with the tetrasubstituted C atom as the flap. The benzene ring of the chromeno ring system is inclined to the benzene ring fused to the latter pyran ring by 74.66 (9) . These aromatic rings are inclined to the 4-methylphenyl ring by 52.67 (9) and 66.63 (10) , respectively. In the crystal, molecules are linked via C-HÁ Á ÁO hydrogen bonds, forming a two-dimensional network parallel to the bc plane.
In the crystal, molecules are linked via C-H···O hydrogen bonds forming a two-dimensional network lying parallel to the bc plane (Table 1 and Fig. 2).

Experimental
A mixture of (E)-methyl 2-((2-formylphenoxy)methyl)-3-(4-methylphenyl) acrylate (0.308 g, 1 mmol) and 4-hydroxy-2H-chromen-2-one (0.162 g, 1 mmol) was placed in a round bottom flask and melted at 453 K for 1 h. After completion of the reaction as indicated by TLC, the crude product was washed with 5 ml of ethylacetate:hexane mixture (1:49 ratio) which successfully provided the title compound as a colourless solid in 97% yield. Diffraction quality crystals were obtained by slow evaporation of a solution in ethyl acetate.

Refinement
The methine and methylene H atoms were located in a difference Fourier map and freely refined. The aromatic and methyl H atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 Å (aromatic) and 0.96 Å (methyl) Å, with U iso (H) = 1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title molecule, with the atom numbering. The displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound. The C-H···O hydrogen bonds are shown as dashed lines [see Table 1 for details; H atoms not involved in these interactions have been omitted for clarity]. 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.