Synthesis and structure elucidation of a series of pyranochromene chalcones and flavanones using 1D and 2D NMR spectroscopy and X-ray crystallography.

A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene-based flavanones using X-ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X-ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C-2.

1-(5-Hy-droxy-2,2,8,8-tetra-methyl-2H,8H-pyrano[2,3-f]chromen-6-yl)-3-(4-meth-oxy-phen-yl)prop-2-en-1-one.

In the biologically active title compound, C26H26O5, the pyran ring of the chromene unit adopts a half-chair conformation. The C=C double bond of the propenone unit exhibits a trans conformation and the carbonyl group is syn conformation to the double bond. The dihedral angle between the benzene ring and the benzopyran-one moiety is 31.54 (4)°. The mol-ecular structure is stabilized by an intra-molecular C=O⋯H-O hydrogen bond.

1-(5-Hy-droxy-2,2,8,8-tetra-methyl-2H,8H-pyrano[2,3-f]chromen-6-yl)ethanone.

In the title compound, C(18)H(20)O(4),the pyran ring of the chromene unit adopts a half-chair conformation. An intra-molecular O-H⋯O hydrogen bond occurs. In the crystal, mol-ecules are linked along the b axis by C-H⋯O hydrogen bonds.

2-Acetyl-phenyl (2E)-3-(4-fluoro-phen-yl)acrylate.

In the title compound, C(17)H(13)FO(3), the dihedral angle between the benzene rings is 70.34 (5)°. In the crystal, molecules are linked via pairs of bifurcated C-H⋯(O,O) hydrogen bonds, forming inversion dimers. These dimers are linked via C-H⋯O and C-H⋯F inter-actions, forming a three-dimensional structure.

(S)-4-tert-Butyl-2-(1,2,3,4-tetra-hydro-isoquinolin-3-yl)-1,3-thia-zole.

In the title compound, C(16)H(20)N(2)S, a potential tetra-hydro-isoquinoline (TIQ) thia-zole ligand, the N-containing six-membered ring of the TIQ unit adopts a half-chair conformation. There are four mol-ecules in the asymmetric unit. No classical hydrogen bonds or π-π inter-actions were found in the crystal structure.

2,4-Dibromo-1,3-dimeth-oxy-5-methyl-benzene.

The title compound, C(9)H(10)Br(2)O(2), crystallizes with two mol-ecules in the asymmetric unit. The two mol-ecules are essentially planar with slight differences in the (Br)C-C-O-C(H(3)) torsion angles [-176.7 (2) and -172.8 (2)° in one mol-ecule and 174.8 (2) and 179.9 (2)° in the other]. The crystal structure consists of sheets of mol-ecules linked through Br⋯Br [3.3547 (4), 3.3703 (4) and 3.5379 (4) Å] inter-actions, which are in turn connected through π-π inter-actions with centroid-centroid distances of 3.5902 (14) and 3.5956 (14) Å.

(S)-4-Phenyl-2-(1,2,3,4-tetra-hydro-isoquinolin-3-yl)-1,3-thia-zole.

In the title compound, C(18)H(16)N(2)S, the N-containing ring adopts a half-chair configuration. The crystal packing features C-H⋯N contacts. There is no π-π stacking within the crystal structure.

2-[(1R,3S)-6,7-Dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinolin-3-yl]-4-phenyl-1,3-thia-zole.

In the title compound, C(26)H(24)N(2)O(2)S, the dihedral angle between the thia-zole ring and the adjacent phenyl ring is 3.02 (15)°. The N-containing six-membered ring of the tetra-hydro-isoquinoline unit adopts a half-chair conformation. The dihedral angle between the least-squares plane of the tetra-hydro-isoquinoline ring system and its nearest phenyl ring is 76.90 (13)°. No classical hydrogen bonds nor π-π inter-actions were found in the crystal structure.