Gram-scale preparation of negative-type liquid crystals with a CF₂CF₂-carbocycle unit via an improved short-step synthetic protocol

Abstract

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.

Chemodivergent Photocatalytic Synthesis of Dihydrofurans and β,γ‐Unsaturated Ketones

“…Among the obtained compounds, 2‐acetyl‐2‐chlorocyclohexan‐1‐one 1 o provided the spiro product 6 oa in good yield (56%) as single diastereoisomer, and 2‐chloro‐2,2‐difluoroacetophenone 1 r quantitatively furnished the fluorinated hemiketal 6 ra . Only Konno and co‐workers obtained products with a similar substituents distribution but exploiting a much longer synthetic pathway [72,75] …”

“…These highly substituted cyclopentyl hemiketals ( 6 ) are useful synthetic intermediates, [71] in particular for the preparation of materials [72] and medicinally relevant molecules [73] . Our approach represents a particularly straightforward synthesis of these scaffolds, which were obtained for the first time in high yield by radical addition of ketones to olefins [74] .…”

“…Only Konno and co-workers obtained products with a similar substituents distribution but exploiting a much longer synthetic pathway. [72,75] Supposing a significant role of water in the formation of these compounds, we repeated the synthesis of 6 qa in MeCN/H 2 O mixture and we gratify-ingly obtained the desired product in quantitative yield (93%). In general, the reactions involving these substrates (1 o-q) were slow (72 hours), probably because the steric hindrance around the radical carbon slowed the addition to the olefin.…”

Synthesis and Characterization of Photoluminescence Liquid Crystals Based on Flexible Chain-Bearing Pentafluorinated Bistolanes

“…Over the past few years, our group has pursued the development of fluorine-containing organic materials and has developed negative-type LC molecules with the CF 2 CF 2 -containing carbocycles A and the mesogenic structure B [17][18][19]. Moreover, the scope of π-conjugated photoluminescence (PL) molecules was extended to include a pentafluorinated aromatic scaffold, as exemplified by fluorinated tolanes C and bistolanes D (Figure 1a) [20][21][22].…”

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

“…In addition to the development of a convenient access to CF 2 CF 2 -containing pyranoses [ 12 ], our group also showed that tricyclic mesogens with a CF 2 CF 2 -containing carbocycle exhibited large negative dielectric anisotropies ( Fig. 1 ), which would be promising for candidates for vertically aligned (VA)-type display materials [ 13 – 17 ]. Owing to such valuable applications, the development of a much more efficient synthetic protocol for CF 2 CF 2 -containing organic molecules has a high priority in various research areas.…”