Crystal structures and conformational analyses of three pyranochromene derivatives

The title compounds, C27H20O6, (I) [systematic name: methyl 7-oxo-14-phenyl-1H,7H,14H-pyrano[3,2-c:5,4-c′]dichromene-14a(6bH)-carboxyl­ate], C24H22O5, (II) [systematic name: methyl 1-oxo-6-phenyl-2,3,4,12b-tetra­hydro-1H,6H-chromeno[3,4-c]chromene-6a(7H)-carboxyl­ate], and C25H23N3O4, (III) [systematic name: 6-(4-ethyl­phen­yl)-2,4-dimethyl-1,3-dioxo-2,3,4,12b-tetra­hydro-1H,6H-chromeno[4′,3′:4,5]pyrano[2,3-d]pyrimidine-6a(7H)-carbo­nitrile], are pyran­ochromene derivatives. The central pyran rings (B) of compounds (I) and (III) adopt half-chair conformations, whereas that of compound (II) adopts a sofa conformation. The pyran rings (A) of the chromene ring systems of compounds (II) and (III) adopt half-chair conformations, while that of compound (I) adopts a sofa conformation. The mean plane of the central pyran rings (B) make dihedral angles of 70.02 (6), 61.52 (6) and 69.12 (7)°, respectively, with the mean planes of the chromene moieties (C+A) of compounds (I), (II) and (III). The bicyclic coumarin ring system (C+A+B+E) in compound (I) is almost planar (r.m.s. deviation = 0.042 A). The carbo­nitrile side chain in compound (III) is very nearly linear, with the C—C≡N angle being 176.6 (2)°. The cyclo­hexene ring (E), fused with the central pyran ring (B) in compound (II) adopts a sofa conformation. In the mol­ecular structures of compounds (II) and (III), there are C—H⋯O short contacts, which generate S(7) ring motifs. In the crystal structures of the title compounds, mol­ecules are linked by C—H⋯O hydrogen bonds, which generate mol­ecular sheets parallel to the ab plane, with R43(28) loops in (I), inversion dimers with R22(10) loops in (II) and chains along [010] with R22(12) ring motifs in (III). In the crystal structures of (I) and (III), there are also C—H⋯π inter­actions present, leading to the formation of a three-dimensional framework in (II) and to sheets parallel to (101) in (III).