NOVEL COMPOUND AND SEPARATING AGENT

Abstract: A compound represented by general formula (I) and a separating agent comprising the same. In formula (I), Ar and Ar' represent each an aromatic group and two substituents on the central benzene ring may be positioned ortho, meta or para to each other. It can separate and purify a variety of compounds and can provide compounds useful in the field of fine chemicals such as intermediates of medicines, in particular, optically active compounds with high purity in large amounts.

Description: The present invention relates to a method for separation or purification using a specific compound (I) described below having a diethynylbenzene skeleton. Further, the present invention relates to a method for separation of optical isomers using a specific compound (I') described below having a diethynylbenzene skeleton. These specific compounds can be used for the separation of various mixtures which are otherwise difficult to separate and therefore can be utilized in the field of fine chemicals. There have been known several substances (hereinafter term "host compounds" according to the custom) which have a property of being combined with a separable compound (hereinafter term "a guest compound" according to the custom) contained in a mixture at a stoichiometric ratio to form a crystal (clathrate compound) and, therefore, have a capacity of separating the guest compound only from the mixture. Examples of such host compounds include compounds represented by the following formula (II): wherein Ar and Ar' are each an aromatic group . Particularly when these host compounds are optically active substances, they are effective in the separation of optical isomers which is generally thought to be one of extremely difficult techniques. However, the kinds of compounds which can be separated by these host compounds were limited. Skowronski, R. et al., Bull. Soc. Chim. Fr., 1967, N° 11, pp. 4235-4243 discloses compounds having a diethynylbenzene skeleton and processes for producing these compounds. JP-A-62-286957 discloses a process for the preparation of optically active propionic acid amides by resolution of a racemic mixture of said amides by 1,6-di(2-halophenyl)1,6-diphenyl-2,4-hexodiyne-1,6-diol. A first object of the present invention was to provide a novel method for separation or purification using a compound having a diethynylbenzene skeleton. This object has been solved by providing a method for separation or purification, said method comprising the step of combining a compound (host compound) represented by the general formula (I) with another compound (guest compound) to form a clathrate compound to thereby separate the guest compound from a mixture or to thereby purify a third substance contaminated with the guest compound; general formula (I): wherein Ar and Ar' are each an aromatic group; and the positional relation of the two substituents on the central benzene ring may be any of ortho, meta and para. A second object of the present invention was to provide a novel method for separation of optical isomers using a compound having a diethynylbenzene skeleton. This object has been solved by providing a method for separation of optical isomers constituting an optical isomer mixture, said method comprising the step of combining an optically active compound (host compound) represented by the general formula (I') with only one of the optical isomers constituting an optical isomer mixture of a guest compound selectively to form a clathrate compound containing the optical isomer to thereby separate the optical isomers of the guest compound; general formula (I'): wherein Ar and Ar' are different aromatic groups; both terminal groups have either of R- and S-configuration; and the positional relation of the two substituents on the central benzene ring may be any of ortho, meta and para. In the general formula (I), aromatic groups represented by Ar and Ar' may be the same or different from each other. In both the general formulae (I) and (I'), each aromatic group preferably has at most 10 carbon atoms. Examples of such an aromatic group include a phenyl group and α- and β-naphthyl groups and groups derived therefrom by substitution (such as an o-chlorophenyl group). The groups derived therefrom may be substituted by any substituents at any position, so far as the ability of the resulting compound as a host compound is not impaired. The structures and stereochemical characteristics of the diarylhydroxymethyl groups present at both ends have a great influence on the separating power of the host compound. When the compound represented by the general formula (I) is used for separation of chemically different substances, for example, that of a mixture of substances having boiling points close to each other or that of a mixture of diastereomers, the absolute configurations of both terminal groups in the case wherein Ar and Ar' are different from each other are not particularly limited, so that the compound may be a so-called mesoisomer wherein one of the terminal groups has R-configuration and the other has S-configuration, or may be a substance wherein both terminal groups have R-configuration, one wherein both terminal groups have S-configuration, an equivalent mixture of both substances, i.e., a so-called racemic modification, or a substance wherein Ar and Ar' may be the same. On the other hand, when the compound of formula (I') is used for separation of optical isomers which is a more sophisticated separation, the compound must be one wherein Ar and Ar' are different from each other and both terminal groups have either of R- and S-configurations, i.e., the compound must be optically active. The compound represented by the above general formula (I) can be most easily prepared by conducting double coupling reaction as represented by the following equation in the presence of a transition metal catalyst, though it may be prepared by any process: wherein Ar and Ar' are each as defined above and X represents a halogen atom . An optically active compound (I') can be prepared from an optical isomer of a compound represented by the formula: ArAr'C(OH)C≡CH without troublesome separation, though it may be prepared by conducting the above double coupling reaction by the use of a racemic modification of a compound represented by the formula: ArAr'C(OH)C≡CH and separating the obtained stereoisomeric mixture (with an optically active guest compound particularly in the separation of optical isomers). The optical isomer may be prepared by any of processes, and the processes include, for example, those described in F. Toda et al., Isr. J. Chem., 25 , 338 (1985) and in J. Chem. Soc., Chem. Commun., 1983 , 743. By utilizing the property of the compound (host compound) used in the present invention represented by the above general formula (I) that the host compound is combined with another compound (guest compound) to form a clathrate compound, the separation of the guest compound from a mixture and the purification of a third substance contaminated with the guest compound can be attained. The separation of the guest compound from a mixture and the purification of a third substance contaminated with the guest compound by the use of the host compound may be conducted by any suitable method. Most generally, suitable amounts of a compound (a guest compound) which is an object of separation and the host compound are dissolved in a solvent; and a clathrate compound (a crystal comprising the host compound and the guest compound at a stoichiometric ratio) is precipitated from the obtained solution by any means selected from among e.g. temperature change, pressure change, evaporation of solvent and addition of poor solvent. Alternatively, a mixture which is an object of separation may be used as the solvent for the host compound. Further, when both guest and host compounds are solid, a clathrate compound is sometimes formed by mere blending. Furthermore, the purity, yield and crystal form of the clathrate compound can be controlled by conducting the crystallization under elevated pressure. When the solid thus prepared exhibits physical properties (such as melting point and crystal form) different from those of each of the starting materials and comprises both starting material, it is evident that a clathrate compound has been formed. Though the recovery of an objective compound from such a clathrate compound can be conducted by any of processes, a process which comprises evaporating only a component having a lower boiling point into another vessel by vacuum distillation is the simplest and easiest one. Recrystallization of the clathrate compound is a suitable means for enhancing the purity of an objective compound, though an objective compound recovered from the clathrate compound may be recrystallized in some case. Further, the formation of a clathrate compound is effective in the removal of unnecessary impurities. Furthermore, when an optically active compound is selected from among those represented by the above general formula (I') to be used as a host compound, there is formed a clathrate compound containing, selectively, one of the optical isomers constituting an isomeric mixture of a guest compound, by which an optical isomer of the guest compound can be separated. Generally, it is known that the interaction between a host compound and a guest compound occurs not only in a crystalline structure but also in a solution. Accordingly, gas or liquid chromatography can also be carried out by using a so-called stationary phase prepared by binding the host compound onto a support by chemical or physical means. The host compound used according to the present invention is different from known compounds represented by the above general formula (II) mainly in respect of the distance between the diarylhydroxymethyl groups, which is presumably the reason why the host compound used in the present invention is effective in the separation of compounds which have been difficult to separate according to the prior art. The host compounds used in the present invention are effective in the separation and purification of more kinds of compounds, which enables the provision of various compounds (such as intermediates of drugs) useful in the field of fine chemicals, particularly optically active substances, at high purities and in large amounts. [Example] The present invention will now be described by referring to the following Examples. In the Examples, Ph represents a phenyl group; Me a methyl group; and Et an ethyl group. Example 1 synthesis of compound (p-I'-1) (compound represented by the formula (I') wherein Ar is a phenyl group and Ar' is an o-chlorophenyl group) : A mixture comprising 53.5 g (0.22 mol) of a compound ([α] D = -139° (MeOH)) represented by the formula: 26.0 g (0.11 mol) of p-dibromobenzene, 0.1 g of PdCl 2 (PPh 3 ) 2 , 0.1 g of CuI, 0.52 g of PPh 3 and 280 ml of Et 3 N was heated under reflux for 4 hours. The resulting mixture was cooled to room temperature by allowing to stand and filtered to remove crystalline Et 3 N·HCl formed. Et 3 N in the filtrate was distilled out on an evaporator. 300 ml of ether was added to the residue and the obtained mixture was washed with diluted hydrochloric acid, water, aqueous sodium hydrogencarbonate and aqueous common salt successively, and dried over anhydrous magnesium sulfate. Acetone was added to the oily substance obtained by distilling out the ether to give a complex (melting point 81 to 82°C) comprising the title compound (p-I'-1) and acetone at a ratio of 1 : 2 as a crystal. This crystal was heated in a vacuum of 133 to 266 Pa (1 to 2 mmHg) at about 120°C for 30 minutes to give 49.3 g (80.2%) of the title compound as a pale-yellow solid. This solid had an obscure melting point and exhibited infrared absorption assignable to ν OH (stretching vibration of hydroxyl group) at 3520 cm -1 and 3400 cm -1 and an optical rotation of -62.6° (c=1.13, MeOH). Example 2 optical resolution of endo-tricyclo[5.2.1.0 2,6 ]deca-3,8-dien-5-one (III) 2.8 g (5.01 mmol) of (-)-(p-I'-1) (Ar is a phenyl group and Ar' is an o-chlorophenyl group) and 1.47 g (10.1 mmol) of a racemic modification of the compound (III) were dissolved in 10 ml of toluene under heating. The obtained solution was allowed to stand at a room temperature for 12 hours to precipitate 2.79 g of a clathrate compound comprising (-)-(p-I'-1) and (+)-(III) at a ratio of 1 : 1 as a crystal. This crystal was recrystallized from toluene twice. 1.45 g of a pale-yellow crystal (melting point 116 to 118°C) thus obtained was heated to 200°C in a vacuum of 133 Pa (1 mmHg) to give 0.30 g of (+)-(III) {[α] D = +140° (c=0.77, MeOH)}. Example 3 resolution of γ-methyl-γ-butyrolactone (IV) 3.02 g of (-)-(p-I'-1) (Ar is a phenyl group and Ar' is an o-chlorophenyl group) and 2.16 g of racemic γ-methyl-γ-butyrolactone (IV) were dissolved in 10 ml of ether, followed by the addition of 5 ml of hexane. The resulting solution was allowed to stand at a room temperature for 12 hours to give 2.8 g of a clathrate compound comprising (-)-(p-I'-1) and (+)-(IV) at a ratio of 1 : 2 as a crystal. This crystal was heated to 200°C in a vacuum to give 0.73 g of (+)-(IV) having an enantiomer excess (e.e.) of 29.1% {[α] D = +8.8° (c=0.64, MeOH)}. Example 4 synthesis of compound (p-I-2) (compound represented by the formula (I) wherein Ar and Ar' are both phenyl groups) : The title compound (p-I-2) was prepared from a compound represented by the formula: and p-dibromobenzene in the same manner as that of the Example 1. The obtained product had a melting point of 216 to 219°C and exhibited infrared absorption assignable to ν OH at 3540 cm -1 . Example 5 synthesis of compound (m-I'-1) (compound represented by the formula (I) wherein Ar is a phenyl group and Ar' is an o-chlorophenyl group) : The title compound (m-I'-1) was prepared from a compound represented by the formula: and m-dibromobenzene in the same manner as that of the Example 1. The obtained product had an obscure melting point and exhibited infrared absorption assignable to ν OH at 3300 cm -1 and an optical rotation [α] D of -95.2° (c=1.0, MeOH). Example 6 synthesis of compound (m-I-2) (compound represented by the formula (I) wherein Ar and Ar' are both phenyl groups) : The title compound (m-I-2) was prepared from a compound represented by the formula: and m-dibromobenzene in the same manner as that of the Example 1. The obtained product had a melting point of 96 to 125°C and exhibited infrared absorption assignable to ν OH at 3230 cm -1 .

Claims: A method for separation or purification, said method comprising the step of combining a compound (host compound) represented by the general formula (I) with another compound (guest compound) to form a clathrate compound to thereby separate the guest compound from a mixture or to thereby purify a third substance contaminated with the guest compound; general formula (I): wherein Ar and Ar' are each an aromatic group; and the positional relation of the two substituents on the central benzene ring may be any of ortho, meta and para. A method for separation of optical isomers constituting an optical isomer mixture, said method comprising the step of combining an optically active compound (host compound) represented by the general formula (I') with only one of the optical isomers constituting an optical isomer mixture of a guest compound selectively to form a clathrate compound containing the optical isomer to thereby separate the optical isomers of the guest compound; general formula (I'): wherein Ar and Ar' are different aromatic groups; both terminal groups have either of R- and S-configuration; and the positional relation of the two substituents on the central benzene ring may be any of ortho, meta and para. The method of claim 2, wherein the optically active compound represented by the general formula (I') is bonded to a stationary phase by chemical or physical means to thereby conduct chromatography on this phase. The use of a compound represented by the general formula (I) in a method for separation or purification.

Inventors: TODA FUMIO, TODA, FUMIO
Applicants: DAICEL CHEM, DAICEL CHEMICAL INDUSTRIES, LTD.
Application year: 1992
Main classification: C07C33
IPC codes: C07B57, C07C45, C07D307, C07C49, C07C33, C07B63