Synthesis of new liquid crystal materials possessing phenylbenzoate or biphenyl core units and (2,3)-epoalkyloxirane methanol chiral tails

#Liquid crystals have found use in a variety of electro-optical and display device applications, in particular those which require compact, energy efficient, voltage-controlled light valves such as watch and calculator displays. These devices are based upon the dielectric alignment effects in nematic, cholesteric, and smectic phases of the crystal compound in which, by virtue of the dielectric anisotropy, the average molecular long axis of the compound takes up a preferred orientation in an applied electric field. Since the coupling of an applied electric field by this mechanism is rather weak, thereby providing the energy efficiency for these devices, the resultant electro-optical response time for these devises is too slow for many other potential applications.

#Liquid crystal displays have a number of unique characteristics, including low voltage and low power of operation, which makes them perhaps the most promising of the non-emissive electro-optical display candidates available with today's technology. However, the slow response and insufficient nonlinearity in liquid crystal displays have been serious limitations to manay potential applications. The lack of speed becomes especially important in proportion to the number of elements that have to be addressed in a device; this results in increasingly impractical production costs for the potential use of such devices in flat-panel displays for use in video display terminals, oscilloscopes, radar, and television screens.

#It has recently been shown (see N. A. Clark and S. T. Lagerwall, Appl. Phys. Lett. 36:899 (1980), and U.S. Pat. No. 4,367,924) that electrooptic effects with submicrosecond switching speeds are achievable using the technology of ferroelectric liquid crystals. Some ferroelectric liquid crystal display structures, in addition to the high speed (about one thousand times faster than currently used twisted nematic devices) reported by these investigators, exhibit bistable, threshold sensitive switching, making them potential candidates for matrix addressed light valves containing a large number of elements for passive display of graphic and pictorial information, as well as for optical processing applications.

#This example illustrates the procedure for coupling of the compounds of Formulas IV and V.

#To a three-neck flask flushed with argon and fitted with a magnetic stir bar was added 30 ml of dry THF, 1,379 gm (6.9 mmol) of p-benzyloxyphenol (the compound of Formula IV), 0.8 gm (6.0 mmol) of (2S,3S)-3-prophloxiranethanol (the compound of Formula V), and 1.98 gm (7.59 mmol) of triphenyl-phosophine. The resulting solution was heated to reflux and 1.2 ml (2.32 gm, 7.59 mmol) of diethyl azodicarboxylate was added over a period of 7 hr. After the addition was complete the reaction mixture was allowed to cool to room temperature and stir for an additional two days under argon. The solvent was then removed, and the residue purified by flash chromatography on silica gel using 85.15 hexanes/ethyl acetate as eluent. In this manner 1.6 gm (78%) of 4-benzyloxy-1-[2S,3S)-epoxyl]-hexyloxybenzene (the compound of Formula VI) was obtained.

#This example illustrates the procedure for debenzylation of compounds of Formula VI.