The C=C double bond in the title compound, C(18)H(15)BrO(4), adopts an E configuration. The two rings are almost orthogonal to each other, making a dihedral angle of 82.8 (1)°. An intra-molecular C-H⋯O hydrogen bond occurs. The crystal structure is stabilized by inter-molecular C-H⋯O hydrogen bonds.

In the title molecular salt, C36H30NP2(+)·C24BF20(-), the P-N bond lengths in the cation are equal [1.573 (2) and 1.572 (2) Å], indicating a resonance structure and the P-N-P bond angle is 144.79 (12)°. In the crystal, weak C-H⋯F interactions link the cations and the anions.

The mol-ecule of the title compound, C(14)H(11)BrClNO, displays an E configuration with respect to the imine C=N double bond. The two aromatic rings are essentially coplanar, forming a dihedral angle of 7.9 (2)°. An intra-molecular O-H⋯N hydrogen bond stabilizes the crystal structure.

In the title compound, C(13)H(9)ClN(2)O(5)S, the N-H bond is trans to the C=O bond. The dihedral angle between the two aromatic rings is 85.4 (1)°. In the crystal, mol-ecules are linked into zigzag C(4) chains along the b axis through N-H⋯O hydrogen bonds.

In the title compound, C(14)H(15)N(3)OS, the phenyl ring is almost perpendicular to the dimethyl-pyrimidine group, with a dihedral angle of 88.1 (3)°. The Csp(2)-S bond of 1.759 (3) Å is significantly shorter than the Csp(3)-S bond of 1.795 (3) Å due to the p-π conjugation.

The title compound, C(16)H(13)FO(2), was prepared from 4-methoxy-hypnone and 4-fluoro-benzophenone by Claisen-Schmidt condensation. All the bond lengths and bond angles are in normal ranges. The dihedral angle formed by the two benzene rings is 33.49 (2)°. The crystal packing is stabilized by inter-molecular C-H⋯O hydrogen-bonding inter-actions.

The Schiff base, C(20)H(14)BrClN(2)O(2), displays a trans conformation with respect to the C=N double bond. The aromatic rings at either end of the -C(=O)-NH-N=C- fragment are nearly parallel [dihedral angle = 3.4 (5)°]. The hydr-oxy group forms an intra-molecular hydrogen bond to the imino N atom.

The title compound, C(15)H(14)O(2), was prepared from 4-methyl-hypnone and 5-methyl-furfural by Clasion-Schmidt condensation. All of the bond lengths and bond angles are in normal ranges. The dihedral angle formed by the benzene ring and furan ring is 5.31 (2).

In the title Schiff base compound, C(13)H(9)Cl(2)NO, the mol-ecule displays an E conformation about the imine C=N double bond, with a dihedral angle of 8.09 (11)° between the two benzene rings. In the crystal, mol-ecules are linked by a single O-H⋯O hydrogen bond, giving one-dimensional chains which extend along (100).

The title compound, C(18)H(27)NO(2), crystallizes as the enamine form with Z geometry. The β-enamino-ester fragment forms a dihedral angle of 87.5 (1)° with the isopropyl-phenyl frame. The structure exhibits an intra-molecular N-H⋯O hydrogen bond. In addition, in the crystal, mol-ecules are linked by a centrosymmetric inter-molecular N-H⋯O hydrogen bond.