The fungicidal activity of β-keto sulfones. Molecular conformation of α-phenylhydrazono-β-ketosulfones as determined by an X-ray analysis

Abstract

The solid-state conformations of eight (1-phenylhydrazono-2-oxo-2-phenylethyl)-phenyl sulfones and four (1-phenyl-1-phenylhydrazono-2-oxo-2 phenylethyl)-phenyl sulfones have been analyzed. All compounds adopt conformations which maximize the gauche or cis type of interaction between the sulfur-oxygen double bonds and large polar substituents situated in α positions with respect to the sulfonyl groups. The charge distribution strongly favours stereoelectronic effects. The conformation of (1-phenylhydrazono-2-oxo-2-phenylethyl)-phenyl sulfones is mostly stabilized by strong, intramolecular, resonance-assisted hydrogen bonds supplemented by charge transfer from β-carbonyl groups towards the sulfonyl groups. In the second group of sulfones, the donation of electron density from N(2) atoms of the hydrazone moiety to the sulfur atoms is the main stereoelectronic interaction.