Crystal structures and conformational analyses of three pyranochromene derivatives

Abstract

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 Å). The carbonitrile side chain in compound (III) is very nearly linear, with the C—C[triple-bond]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).

Keywords

• crystal structure
• pyranochromene
• coumarin derivatives
• molecular sheets
• inversion dimers
• chains
• hydrogen bonding