CS276069B6 - Process for purifying optically active l-4'-(4''-pentylcarbonyloxyphenyl)phenyl ester of 4-methyl-2-chloropentanoic acid - Google Patents

Abstract

Crude product optical active L-4 * - (4 ") -pentylcarbonyloxyphenyl) phenyl ester ky # seliny 4-methyl-2-chloropentanoic acid ss rozpus # tí ve aněei 90 to 70 % Art. toluene and 10 to 30 % Art. ethanol, načež ae rozdě # if on chronatografické column, přlčeaž ae Individual folders gradually eluujl listed sněsl toluene and ethyl alcohol and folders obsa # tive optical active substance ae apojl and after evaporation ee prekryataluji from clean hexane.

Description

The present invention relates to a process for the purification of optically active 4-methyl-2-chloropentanoic acid L-4 '- (4-pantylcarbonyloxyphenyl) phenyl ester prepared from optically active 4-methyl-2-chloropentanoic acid and 4- (4'-pentylcarbonyloxyphenyl). phenol. Purification consists in separating the optically inactive component 4- (4 * -pentylcarbonyloxyphenyl) phenol, which reduces the specific rotation of the liquid crystal. The optically active L-4 '- (4-pentylcarbonyloxyphenyl) phenyl ester of 4-methyl-2-chloropentanoic acid is one of the novel diester compounds of the biphenyl type with the general formula ’

IIii.

RC-OCH.-C _c H.-ocr ;?

Λ O 4 D 4 &

wherein R * is alkyl representing a source of optical activity (Sakurai T. et al., Ferroelectrics 85, 469 (1988) »Shinozaki Y., Shibata T., and Kimura M. with OP 63 230 649» CA IIP. 75044 (1989)) . The compounds of the above formula are chemically stable, maintain aeroelectric properties over a wide temperature range and have a high dielectric constant. The preparation of these compounds is described by a team of Japanese authors (Higuchi R.), Sakurai T., Mikami N., Akaiwa®. »Takeuchi K. with EP 0174816 (1985). .

This disadvantage is eliminated by the process for purifying the optically active L-4 * - (4-pantylcarbonyloxyphenyl) phenyl 4-methyl-2-chloropentanoate according to the invention, which consists in dissolving the crude product in a mixture of 90 to 70% by volume. of toluene and 10 to 30% by volume of ethyl alcohol, after which it is separated on a chromatographic column, the individual components being eluted successively with said mixture of toluene and ethyl alcohol. The components containing the optically active substance are combined and, after evaporation, the crystals obtained are recrystallized from pure hexane.

According to the process of the invention, very pure 4-methyl-2-chloropentanoic acid L-4- (4-pentylcarbonyloxyphenyl) phenyl ester can be prepared with a reproducible specific rotation g® -15.57 ° (5.6% solution in chloroform).

Example g of a contaminated product containing optically active L-4 '- (4-pentylcarbonyloxyphenyl) phenyl ester of 4-methyl-2-chloropentanoic acid and optically inactive 4- (4'-pentylcarbonyloxyphenyl) phenol is dissolved in 200 ml of a mixture containing 80% by volume. of toluene and 20% by volume of ethyl alcohol. 15 ml of this solution are transferred to a chromatographic column 400 mm long with an internal diameter of 32 mm, which contains silica for chromatography (Kieselgel 60, Merck). The two compounds contained in the solution are separated on this column and mixtures containing 80% by volume of toluene and 20% by volume of ethyl alcohol are eluted successively. The total volume of the elution mixture is 400 ml per 15 ml of the original solution. Control of the separation of ee is carried out by thin-layer chromatography using Silufol films (s.p. Lachema) and the spots are detected by ultraviolet radiation and an eluent. When optically, the optically active substance elutes first. Chromatographic separation is carried out until a large amount of 200 ml of the original solution is processed. The individual fractions containing the optically active substance are combined and the eluent is evaporated to a small volume on a rotary evaporator. The concentrated ee solution is poured in a thin layer into the bottom of the beaker and carefully evaporated to dryness in a vacuum oven. The obtained crystals were recrystallized from pure hexane.

Overall yield was 1.33 kg of fine white crystals of pure ^L-4 '- (4-pentylkarbonyloxyfenyl) phenyl ester of 4-methyl-2-chlorpentanové whose structure was confirmed by nuclear magnetic resonance and infrared epektrometrií.

Claims (1)

PATENT CLAIMS Process for the purification of optically active L-4 * - (4-pentylkerbonyloxyphenyl) phenyl ester of 4-methyl-2-chloropentanoic acid, characterized in that the crude product is dissolved in a mixture of 90 to 70% by volume of toluene and 10 to 30% by volume of ethyl alcohol , then separated on a chromatographic column, the individual components being eluted successively with the above mixture of toluene and ethyl alcohol, and the components containing the optically active substance were combined and, after evaporation, recrystallized from pure hexane.