In the title mol-ecule, C(18)H(12)O(4), the phenyl ring is twisted by 23.2 (1)° from the mean plane of the chromene system. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into zigzag chains extending in the [010] direction. An intra-molecular O-H⋯O hydrogen bond is also present.

In the title compound, C(21)H(18)O(4), tthe dihedral angle between the chromene ring system and the pendant phenyl ring is 6.1 (1)°. The crystal structure is stabilized by an intermolecular C-H⋯O and C-H⋯π inter-actions.

In the title compound, C13H12O5, the mean plane of the 2H-chromene ring system (r.m.s deviation = 0.026 Å) forms a dihedral angle of 81.71 (6)° with the mean plane of ethyl 2-hy-droxy-acetate moiety (r.m.s deviation = 0.034 Å). In the crystal, C-H⋯O hydrogen bonds result in the formation of zigzag layers parallel to the bc plane.

In the title compound, C(27)H(27)NO(4), the five-membered isoxazole ring adopts an envelope conformation and the six-membered pyran ring adopts a half-chair conformation. The dihedral angle between the mean planes of the isoxazole ring and the chromene ring system is 54.95 (4)°.

In the title compound, C(17)H(10)Br(2)O(5), the chromene ring is almost planar with minimal puckering [total puckering amplitude = 0.067 (4) Å]. The dihedral angle between chromeme ring system and phenyl ring is 3.7 (2)°. The crystal structure is stabilized by intermolecular C-H⋯O inter-actions and an intramolecular O-H⋯O hydrogen bond also occurs.

A rapid, clean, and highly efficient method for synthesis of dihydropyrano[3,2-c]chromene derivatives by one-pot, three-component condensation of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin using DABCO as catalyst in solvent-free neat conditions is described. The present method has the advantages of mild reaction conditions, short reaction times, easy isolation of products, and exc...

In the title mol-ecule, C(18)H(15)NO(4), the benzoate ring is oriented at a dihedral angle of 43.43 (6)° with respect to the planar [maximum deviation = 0.038 (2) Å] chromene ring. The crystal structure features R(2) (2)(12) centrosymetric dimers formed via C-H⋯O inter-actions and these dimeric aggregates are connected by C-H⋯π inter-actions.

A novel method for the preparation of (±)-methyl 1,1a,2,7b-tetrahydro-2-oxocyclopropa[c] chromene-1a-carboxylate has been developed. The cyclopropanation of methyl coumarin-3-carboxylate provided title compound in moderate yield by dropwise treatment with 1.5 equiv. of dimethylsulfoxonium methylide over 6 h. The structure of the newly synthesized compound was determined using 1H-, 13C-NMR, IR a...

The mol-ecular conformation of the title compound, C(10)H(8)O(4), isolated from Laretia acualis, is stabilized by a strong intra-molecular hydrogen bond between the hydroxyl and carbonyl groups. The crystal packing shows π-π stacking inter-actions. The chromene (4H-1-benzopyran-4-one) unit is essentially planar.