Soh-ichi Kitoh

Crystal structures and conformations of 5-benzyl-2-thiohydantoin and its 1-acetylated derivative

ABSTRACT The crystal structures of 5-benzyl-2-thiohydantoin (5-BTH) and 1-acetyl-5-benzyl-2-thiohydantoin (1-Ac-5-BTH) have been determined by X-ray diffraction. In the 5-BTH crystals, the enantiomeric (R)- and (S)-5-BTH molecules are connected to form cyclic dimers via the hydrogen bonds of the thioamide and the amide moieties. On the other hand, the intermolecular hydrogen bonds in 1-Ac-5-BTH crystals form an infinite chain. These differences in the hydrogen bond pattern are also discussed in the IR and Raman spectra. The ab initio molecular orbital calculations (Gaussian 03) with 6-31G(d,p) basis set were carried out for 5-BTH and 1-Ac-5-BTH to get the preferred conformation.

Crysatl and Molecular Structures of Racemic and Chiral 4-Phenyl-1,3-thiazolidine-2-thiones

The crystal and molecular structures of (rac)- and (S)-4-phenyl-1,3-thiazolidine-2-thiones (4-PTT) have been studied by X-Ray diffraction and ab initio MO calculations at the level of HF/6-31G*. In racemic crystals, the thioamide groups of the enantiomeric (R)- and (S)-4-PTT pairs are hydrogen-bonded around a crystallographic center of symmetry to form a planar cyclic dimer. On the other hand, in (S)-4-PTT crystals, a cyclic dimer through the hydrogen bonding is formed between the two independent molecules (molecules A and B) in the asymmetric unit and its geometry is distorted.

5-Isopropyl-5-methyl-2-sulfanylidene­imidazolidin-4-one

In the title compound, C7H12N2OS, the 2-sulfanylideneimidazolidin-4-one moiety is nearly planar, with a maximum deviation of 0.054 (2) Å. In the crystal, a pair of N—H⋯O hydrogen bonds and a pair of N—H⋯S hydrogen bonds each form a centrosymmetric ring with an R 2 2(8) graph-set motif. The enantiomeric R and S molecules are alternately linked into a tape along [1-10] via these pairs of hydrogen bonds.

1-Acetyl-5-(4-fluoro-phen-yl)-2-sulfanyl-ideneimidazolidin-4-one.

In the title compound, C11H9FN2O2S, the 2-sulfanylideneimidazolidin-4-one moiety is essentially planar, with a maximum deviation of 0.0183 (14) Å. The mean plane of this moiety is approximately coplanar with the attached acetyl group and perpendicular to the benzene ring, making dihedral angles of 9.70 (14) and 86.70 (6)°, respectively. In the crystal, molecules are linked by N—H⋯O hydrogen bonds between the amide NH and acetyl C=O groups, forming a C(6) chain along the a-axis direction.