In the title compound, C(10)H(5)FO(3), the chromenone ring is essentially planar, with a maximum deviation of 0.039 (1) Å. The dihedral angle between the fluoro-subsituted benzene ring and the pyran ring is 1.92 (4)°. In the crystal, mol-ecules are connected via weak inter-molecular C-H⋯O hydrogen bonds, forming supra-molecular ribbons along the b axis. These ribbons are stacked down the a axis.

The asymmetric unit of the title solvate, C(20)H(25)ClO(9)S·0.25CH(3)OH, contains one galactopyranosyl derivative and one-quarter of a methanol solvent mol-ecule. The galactopyran-ose ring is in the usual (4)C(1) conformation, and the anomeric center of the sugar has a β configuration. The value of θ (3.44°) and the range of torsion angles [or 53.1 (5)-63.0 (5)°] reflect a slight distortion of ...

In the title compound, C(25)H(25)NO(3), the dihydro-pyran ring adopts a half-chair conformation, whereas the pyrrolidine ring is in a twist conformation. The tolyl group is oriented at an angle of 82.92 (7)° with respect to the napthalene ring system. In the crystal structure, mol-ecules are linked into centrosymmetric dimers by C-H⋯π inter-actions involving the benzene ring of the tolyl group.

The Prins reaction was investigated using BF₃.OEt₂ as a Lewis acid. It has been recently demonstrated, that if BF₃.OEt₂ is used in stoichiometric amounts then these reactions generate fluorinated products where the BF₃.OEt₂ contributes fluoride ion to quench the intermediate carbocations. In this study oxa- and aza-Prins reactions for the synthesis of 4-fluoro-pyrans and -piperidines were inves...

The mol-ecular structure of the title compound, C(19)H(20)O(2), reveals a slightly distorted chair conformation for the tetra-hydro-pyran ring with the two methyl and two phenyl substituents in equatorial positions.

In the title compound, C(17)H(14)O(3), the pyran ring adopts a boat conformation and the dihedral angle between the aromatic ring planes is 59.1 (1)°. In the crystal structure inter-molecular C-H⋯O hydrogen bonds and C-H⋯π inter-actions link the mol-ecules.

In the title compound, C(19)H(19)NO(2), commonly called koenimbine, the pyran ring adopts a sofa conformation. The carbazole ring system is planar [r.m.s. deviation = 0.063 (1) Å]. A C(10) zigzag chain running along the b axis is formed through inter-molecular C-H⋯O hydrogen bonds. The chains are linked via weak C-H⋯π and N-H⋯π inter-actions.

In the title compound, C(22)H(21)NOS, the thio-pyran-one ring adopts a chair-like conformation with the substituent in the axial position. The relative configuration of the racemic compound is 3R,7S according to the numbering scheme used in this publication. In the crystal packing, centrosymmetric dimers are built up via N-H⋯O hydrogen bonds, with graph set R(2) (2)(8).

The title compound, C(14)H(19)NO(6), was synthesized by the condensation reaction between hecilid (4-formyl-phenl-β-d-allopyran-oside) and methyl-amine in methanol. In the crystal structure, the pyran ring adopts a chair conformation and adjacent mol-ecules are linked by inter-molecular O-H⋯O and O-H⋯N hydrogen bonds, forming a three-dimensional network.