John Tierney

Fungicidal and spectral studies of some triphenyltin compounds

In the interest of developing a more effective fungicide to combat Dutch elm disease, our laboratories have synthesized several triphenyltin carboxylates and some 1:1 addition compounds of triphenyltin chloride using 2,3-disubstituted thiazolidin-4-ones as the ligand and screened them in vitro against Ceratocystis ulmi, the causative agent of Dutch elm disease, using a shake culture method. Elemental analyses and spectroscopic data indicate that the structures of the carboxylates in the solid state are monomeric with a tetrahedral tin atom with the exception of the furan-2-carboxylic acid derivative, which was found to be polymeric. The triphenyltin chloride adducts are trigonal-bipyramidal with the three phenyl groups in the equatorial plane. Far-infrared data indicate that the three phenyl groups are not co-planar. Screening results for both series of organotins indicate that these two classes of compounds are effective inhibitors of Ceratocystis ulmi, with the adducts having a higher activity. The furan-2-carboxylic acid derivative has a markedly decreased activity compared with the other carboxylates and this is attributed to its polymeric structure.

Molecular Structure and Fungicidal Activity against Ceratocystis ulmi of the 1:1 Adducts of Triphenyltin Chloride and 2,3‐Disubstituted Thiazolidin‐4‐ones

Several 1 : 1 addition compounds between triphenyltin chloride and 2,3-disubstituted thiazolidin-4-one ligands have been synthesized. Their molecular structure has been deduced using far IR and Mossbauer spectroscopies. In addition, molecular modeling of several of the complexes was used to explain the variation of the quadrupole splitting values in the Mossbauer spectra. The structures of the complexes were determined to be trigonal-bipyramidal with the three phenyl groups in the equatorial plane. However, the phenyl groups are not co-planar, on the basis of the observation of both the Sn-C (phenyl) symmetric and asymmetric stretching vibrations. The adducts were screened against the fungus Ceratocystis ulmi, the agent responsible for Dutch elm disease, and found to be effective in the inhibition of this fungus. The toxicity of the adducts varied with the hydrophobicity of the molecule. A direct correlation between substitution on the phenyl group on the thiazolidine ring and the toxicity of the compound was not observed.

Effects and Conformational Analysis of Some Substituted 2,3-Diphenyl-1,3-thiazolidin-4-ones

Substituents placed on the phenyl rings of 2,3‐diphenyl‐1,3‐thiazolidin‐4‐one affect the electron density surrounding both the methine proton and the C(2) carbon. These changes are reflected in the differing chemical shifts for these atoms relative to the parent compound. The other carbons in the heterocyclic ring appear to be similarly affected by substituents on the phenyl rings. Correlations for the effects of various substituents in both the 2‐ and 3‐phenyl rings with the 1H and 13C chemical shifts for the aforementioned sites are discussed using both Hammett and Swain–Lupton dual parameter methods. A conformational analysis using ab initio calculations is in agreement with the observed NMR data.

2-(3-Nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one.

The title compound, C20H14N2O3S, has three aromatic rings, viz. (i) a phenyl ring, (ii) a 3-nitrophenyl and (iii) a 1,3-benzothiazine fused-ring system. The dihedral angle between (i) and (ii) is 85.31 (15)°, between (ii) and (iii) is 81.33 (15)° and between (i) and (iii) is 75.73 (15)°. The six-membered 1,3-thiazine ring has an envelope conformation with the C atom in the 2-position forming the flap. In the crystal, molecules are linked by weak C—H⋯O interactions, forming a three-dimensional network.

Crystal structures of 2,3-bis-(4-chloro-phen-yl)-1,3-thia-zolidin-4-one and trans-2,3-bis-(4-chloro-phen-yl)-1,3-thia-zolidin-4-one 1-oxide.

In the related title compounds, (1) and (2), the 3-thiazolidine ring pucker is twisted on the S—Cmethine bond in (1), while in (2), the ring has an envelope conformation with the S atom as the flap. In the crystal of (1), molecules are linked by C—H⋯O hydrogen bonds forming chains along [100], while in the crystal of (2), molecules are linked by C—H⋯O and C—H⋯Cl hydrogen bonds forming slabs parallel to (001).

2,3-Diphenyl-1,3-thia-zolidin-4-one.

The title compound, C15H13NOS, is a chiral molecule crystallized as a racemate, with two molecules in the asymmetric unit. In each of the molecules, the five-membered thiazine ring has an envelope conformation, with the S atom forming the flap. In one molecule, the angle between the two phenyl-ring planes is 82.77 (7)°, while in the other it is 89.12 (6)°. In the crystal, molecules are linked into chains along the b-axis direction by C—H⋯O hydrogen bonds.

Crystal Structures of 1,3-Thiaza-4-one Heterocycles

The five-, six-, and seven-membered 1,3-thiaza-4-one heterocycles are known for their bioactivity. Five-membered 1,3-thiazolidin-4ones are known to have a very wide range of biological activity, so much that the ring system has been referred to as a “magic moiety” or “wonder nucleus” [1]. Six-membered 1,3-thiazin-4-ones have often been investigated for their biological activity and are of potential medicinal use [2]. The activity of seven-membered 1,3-thiazepan-4-ones is exemplified by the investigational compound omapatrilat [3]. Crystal structures of 1,3-thiaza-4-one heterocycles recently obtained in our laboratory will be presented.