Multivicinal fluorine substitution of the cyclohexane ring

Abstract

Highly polar organic fluorinated motifs are of interest in materials chemistry, for example, in liquid crystal applications. Cyclohexane is an important and widely used structural motif within organic chemistry. Work has been carried out to prepare single stereoisomers of multivicinal fluorinated cyclohexanes, a class of compounds that has not been previously produced. A synthesis of the all-syn-1,2,3,4-tetrafluorocyclohexane, in 9 steps from cyclohexa-1,3-diene will be presented. The ¹⁹F NMR spectra of the all-syn-1,2,3,4-tetrafluorocyclohexane shows interesting dynamic conformational effects. This is a small polar organic molecule, which was crystalline at room temperature. The structure of the compound was confirmed by single crystal X-ray diffraction studies. The synthesis of the all-syn-1,2,4,5-tetrafluorocyclohexane from cyclohexa-1,4-diene is also presented. The synthesis of a single diastereoisomer of 1,2,3,4,5,6-hexafluorocyclohexane, derived from benzene in 5 steps, is presented. As with the tetrafluoro compounds, the ¹⁹F NMR spectra of this compound shows dynamic conformational effects. The structure of the compound was confirmed by single crystal X-ray diffraction studies. The 1,2,4,5-tetrafluorocyclohexane motif was elaborated to contain a phenyl group, producing “rod-like” molecules. This motif was synthesised in view of potential applications for liquid crystalline materials.