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Herein, we demonstrate an improved short-step protocol for the synthesis of multicyclic molecules having a CF2CF2-containing cyclohexadiene or cyclohexane framework in a mesogenic structure. These molecules are promising candidates for vertical alignment (VA)-mode liquid crystal (LC) display devices owing to their large negative dielectric constant. The tetrafluorinated multicyclic molecules were successfully obtained in only five or six reaction steps without the need for special handling techniques, as is generally required for thermally unstable organometallic species, representing a reduction of three reaction steps. The improved short-step synthetic protocol was also amenable to the multigram preparation of these promising molecules, which may contribute significantly to the development of novel negative-type LC molecules containing CF2CF2 carbocycles.

Guided by theoretical calculations, we predicted that 5,5,6,6-tetrafluoro-1-methoxycyclohex-1-ene, a new structural motif, exhibits a large negative dielectric anisotropy, and then developed a synthetic strategy for the preparation of the novel tetrafluorinated tricyclic mesogen in twelve reaction steps starting from a commercially available fluorinated starting material. During the evaluation of its liquid-crystalline characteristics, the tetrafluorinated mesogen was found to display low birefringence and a large negative dielectric anisotropy, confirming that its molecular structure is a reasonable design for the further development of novel mesogenic molecules with large negative dielectric anisotropies.

A Novel Synthesis of Fluorine-Containing Cyclopentenones via Pauson-Khand Reaction. -Inter-as well as intramolecular Pauson-Khand reactions of fluorinated alkynes furnishing the desired bicyclic products in good yield are described. -(KONNO*, T.; KIDA, T.; TANI, A.; ISHIHARA, T.; J. Fluorine Chem. 144 (2012) 147-156, http://dx.