JP4604380B2 - Separation of tetramethyl cis-dicyclohexyl-3,3'4,4'-tetracarboxylate - Google Patents

Description

【０００８】
前記の出発物質として用いるＢＰＴＭは、例えば特公昭６０‐３３３７９号公報に記載のフタル酸ジメチルを酸素、パラジウム塩および１，１０−フェナントロリンまたはビピリジルの存在下にカップリングさせてビフェニル化合物を製造する方法によって容易に合成することができる。
【０００９】
前記の水素還元は公知の方法が適用できて、溶媒としてはメタノ−ル、エタノ−ル、ブタノ−ル、酢酸エチル、テトラヒドロフランなどの通常の有機溶媒が使用できる。溶媒の使用量はＢＰＴＭが十分溶解する量であれば特定されないが、通常、１０ｇのＢＰＴＭに対して２５〜１００ｍＬである。
【００１０】
前記水素還元には、触媒として０．１〜１０重量％担持のＲｕ／Ｃ（カ−ボン）、Ｒｈ／Ｃ、Ｐｄ／Ｃ、あるいは、これらのアルミナ担持体、シリカ担持体などを使用できる。触媒量は１０ｇのＢＰＴＭに対して０．１〜０．５ｇで十分である。反応条件としては、常圧でも進行するが、速度をあげるためには、加圧下に行う方がよく、２〜１００気圧、好ましくは１０〜５０気圧で十分である。反応温度は５０〜２５０℃、好ましくは１００〜２００℃で行う。反応を完結するために１〜１０時間の反応を行う。反応は水素の吸収が終了するまで行い、通常、１００℃では５時間程度で終了する。反応方法に限定されないが、水素を連続的に追加供給するとよい。
【００１１】
反応液から濾過などの操作で触媒を除いた後、溶媒を除去すると粘凋な固体が生成物として残る。
この生成混合物から，ｃｉｓ‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ）は適当な溶媒中にて再結晶、または、減圧下に蒸留して、特定留分を集めることで得られる。
【００１２】
前記の再結晶に使用する溶媒はメタノ−ル、エタノ−ル、ブタノ−ル、酢酸エチル、テトラヒドロフランなどの通常の有機溶媒が使用できる。その使用量は、この生成物１００ｇ当たり２００〜１０００ｍＬである。
この際、ｃｉｓ異性体が優先的に析出する。キャピラリ−クロマトグラフィ−（ＣＧＣ）では、単一ピ−クを示すが、高速液体クロマトグラフィ−（ＨＰＬＣ）ではＣｈｉｒａｌｃｅｌＯＤまたはＣｈｉｒａｌｐａｋ ＡＳカラムを用いて分析すると３本のピ−クを示した。そこで、このｃｉｓ異性体を通常の優先晶出法により分割した。
【００１３】
この分離に使用する溶媒はメタノ−ル、エタノ−ル、ブタノ−ル、酢酸エチル、テトラヒドロフランなどを使用できる。使用量に限定はないが、１００ｇ当たり２００〜５００ｍＬ程度で繰り返し晶析して、純品の異性体を得ることができる。
構造は単結晶を生長させることにより、最終的にはＸ線解析から決定することができる。
【００１４】
この発明の１Ｒ，１’Ｓ，３Ｒ，３’Ｓ，４Ｓ，４’Ｒ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｘ）の化学式を次に示す。
【００１５】
【化２】

【００１６】
この発明における（１Ｒ，１’Ｒ，３Ｒ，３’Ｒ，４Ｓ，４’Ｓ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｙ）は、次の化学式で表わすことができる。
【００１７】
【化３】

【００１８】
この発明における（１Ｓ，１’Ｓ，３Ｓ，３’Ｓ，４Ｒ，４’Ｒ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｚ）は、次の化学式で表わすことができる。
【００１９】
【化４】

【００２０】
上記の三種の異性体混合物を分離するに際して、予め液体クロマトグラフィ−（組成比は面積比から求める。）によって求めたｃｉｓ‐ＤＣＴＭ‐ｘの組成比とｘ結晶の溶解開始温度（Ｔｄ）およびｘ結晶の生長開始温度（Ｔｃ）との関係を示すグラフを作成しておき、別途に液クロマトグラフィ−によって求めた異性体混合物のそれぞれの組成比に対応するｘ結晶の溶解開始温度（Ｔｄ）とｘ結晶の生長開始温度（Ｔｃ）の範囲内の温度でｘ種晶を添加する。Ｔｄより高温で種晶を添加すると種晶が溶液中に拡散してしまい、結晶化させるのに不利である。
Ｔｃより低温で種晶を添加すると、結晶化した製品の純度が低下する。
【００２１】
次いで、ｂ）結晶を析出させる温度（Ｔｍ）を下記式の範囲にて操作する。
式：１０℃≦（Ｔｃ−Ｔｍ）≦２５℃。
この温度差が１０℃より小さいと結晶の析出が遅くなる。この温度差が２５℃より大きいと結晶の純度が低下する。
この際に、ｃ）析出時間を３０時間以下、好適には１０〜３０時間とする。１０時間より短くても結晶は析出するが、収量が少ない。３０時間より長いと結晶の純度が低下する。
【００２２】
次いで、同様にしてｃｉｓ‐ＤＣＴＭ‐ｙｚの組成比とｙｚ結晶の溶解開始温度（Ｔｄ）およびｙｚ結晶の生長開始温度（Ｔｃ）との関係を示すグラフを作成しておき、別途に液クロマトグラフィ−によって求めた異性体混合物のそれぞれの組成比に対応するｙｚ結晶の溶解開始温度（Ｔｄ）とｙｚ結晶の生長開始温度（Ｔｃ）の範囲内の温度で種晶を添加する。
次いで、ｂ）結晶を析出させる温度（Ｔｍ）を下記式の範囲にて操作する。
式：１０℃≦（Ｔｃ−Ｔｍ）≦２５℃。
この際に、ｃ）析出時間を３０時間以下、好適には１０〜３０時間とする。
【００２３】
この発明の分離法によって、ｃｉｓ‐ＤＣＴＭ−ｘおよびｃｉｓ‐ＤＣＴＭ−ｙｚ（ラセミ体）のそれぞれを高純度で、高効率で得ることができる。
【００２４】
【実施例】
以下、実施例によってこの発明を具体的に説明するが、この発明はこれらの実施例に限定されるものではない。
以下の実施例において、 高速液体クロマトグラフィ−は島津ＳＣＬ−１０Ａ、カラム：Ｃｈｉｒａｐａｋ ＡＳ（ダイセル化学工業）０．４６ｃｍφ、２５ｃｍ、２０℃、ＥｔＯＨ／ｎ−ｈｅｘａｎｅ（１０／９０）、０．５ｍＬ／ｍｉｎにて測定した。
【００２５】
結晶の溶解開始温度および結晶の生長開始温度の測定
１００ｍＬの試験管に純品のｘ成分およびｙｚ成分を特定の重量比に調製し（総量６ｇ）、これにＴＨＦ１２ｍＬを添加、一旦均一溶液にして密栓した。温度調節器付きバス中に、この試験管を装入して、種晶ｘを加えて、その種晶ｘの溶解開始温度および種晶ｘの生長開始温度を目視にて測定した。この結果から求めたｃｉｓ‐ＤＣＴＭ‐ｘの割合（重量％）と溶解開始温度（Ｔｄ）および結晶の生長開始温度（Ｔｃ）との関係を示すグラフを図１（ｘ成分基準）に示した。同様にして、種晶ｙｚを加えて、その種晶ｙｚの溶解開始温度および種晶ｙｚの生長開始温度を目視にてを測定した。この結果から求めたｃｉｓ‐ＤＣＴＭ‐ｙｚの割合（重量％）と溶解開始温度（Ｔｄ）および結晶の生長開始温度（Ｔｃ）との関係を示すグラフをを図２（ｙｚ成分基準）に示した。
【００２６】
実施例１
５００ｍＬ回転式オ−トクレ−ブに１００ｇのＢＰＴＭ、２．５ｇの５％Ｒｈ／Ｃ、およびテトラヒドロフラン２００ｍＬを仕込み、水素３０ｋｇ／ｃｍ²の定圧下に１００℃で、３００ｒｐｍにて５．５時間、加熱した（約５時間で水素の吸収が終了）。反応液をＮｏ５ｃのろ紙を用いて濾過した後、テトラヒドロフランを留去して１０１．８ｇ（収率９９％）の粘凋な生成物を得た。これを４００ｍＬのメタノ−ルに溶解させて晶析させて、７２ｇのｃｉｓ‐ＤＣＴＭを得た。高速液体クロマトグラフィ−の分析より、ｃｉｓ‐ＤＣＴＭ（ｘ／ｙ／ｚ）＝（５０／２５／２５）であった。４バッチ同様な操作を行い、ｃｉｓ‐ＤＣＴＭ結晶を単離した。
【００２７】
このうち、２００ｇのｃｉｓ‐ＤＣＴＭ結晶（ｃｉｓ‐ＤＣＴＭ−ｘ／ｙｚ＝５０／５０）を採取し、テトラヒドロフラン４００ｍＬに溶解させた。溶液を２８℃にした後、微量の種晶ｘを上記溶液に添加し、これを１０℃にて２０時間静置、保持した。２９．２ｇの結晶（Ａ）を分離し、そのｘ成分の比率は９７．３％であった。濾液（Ｌ）の異性体組成はｘ／ｙｚ＝４５／５５であった。Ａをさらにテトラヒドロフラン５８ｍＬに溶解させて、４８℃にて種晶ｘを添加して２５℃にて２０時間静置、保持した。１８．８ｇの結晶（Ｂ）を分離し、そのｘ成分の比率は１００％であった。
【００２８】
Ｌの溶液を結晶／ＴＨＦ比１／２（１８１ｇ／３６２ｍＬ）まで蒸発して、溶液を２５℃にした後、微量の種晶ｙｚを上記溶液に添加し、これを５℃にて２０時間静置、保持した。２２．８ｇの結晶（Ｍ）を分離し、そのｙｚ成分の比率は９６．０％であった。Ｍをさらに、テトラヒドロフラン４６ｍＬに溶解させて、４０℃にて種晶ｙｚを添加して１８℃にて２０時間静置、保持した。１４．０ｇの結晶（Ｎ）を分離し、そのｙｚ成分の比率は１００％であった。
【００２９】
実施例２
実施例１と同様の操作によって得られたｃｉｓ‐ＤＣＴＭ結晶（ｃｉｓ‐ＤＣＴＭ−ｘ／ｙｚ＝５０／５０）を２００ｇ採取し、テトラヒドロフラン４００ｍＬに溶解させた。溶液を２８℃にした後、微量の種晶ｘを上記溶液に添加し、これを５℃にて２０時間静置、保持した。３７．３ｇの結晶（Ａ）を分離し、そのｘ成分の比率は９６．３％であった。濾液（Ｌ）の異性体組成はｘ／ｙｚ＝３９／６１であった。Ａをさらにテトラヒドロフラン７５ｍＬに溶解させて、４７℃にて種晶ｘを添加して２７℃にて２０時間静置、保持した。２３．３ｇの結晶（Ｂ）を分離し、そのｘ成分の比率は１００％であった。
【００３０】
Ｌの溶液を結晶／ＴＨＦ比１／２（１６２ｇ／３２４ｍＬ）まで蒸発して、溶液を３０℃にした後、微量の種晶ｙｚを上記溶液に添加し、これを３℃にて２０時間静置、保持した。３１．６ｇの結晶（Ｍ）を分離し、そのｙｚ成分の比率は９７．５％であった。Ｍをさらに、テトラヒドロフラン６３ｍＬに溶解させて、４０℃にて種晶ｙｚを添加して１７℃にて２０時間静置、保持した。２０．４ｇの結晶（Ｎ）を分離し、そのｙｚ成分の比率は１００％であった。
【００３１】
【発明の効果】
この発明によれば、ポリイミド樹脂などの原料であるテトラカルボン酸ジ無水物の前駆体として有用な（１Ｒ，１’Ｓ，３Ｒ，３’Ｓ，４Ｓ，４’Ｒ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｘ）の高純度品および、（１Ｒ，１’Ｒ，３Ｒ，３’Ｒ，４Ｓ，４’Ｓ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｙ）と（１Ｓ，１’Ｓ，３Ｓ，３’Ｓ，４Ｒ，４’Ｒ）‐ジシクロヘキシル‐３，３’４，４’‐テトラカルボン酸テトラメチル（ｃｉｓ‐ＤＣＴＭ‐ｚ）とのラセミ体の高純度品を分離取得することができる。
【図面の簡単な説明】
【図１】図１は、ｃｉｓ‐ＤＣＴＭ‐ｘの割合（重量％）と溶解開始温度（Ｔｄ）および結晶の生長開始温度（Ｔｃ）との関係を示すグラフである。
【図２】図２は、ｃｉｓ‐ＤＣＴＭ‐ｙおよびｃｉｓ‐ＤＣＴＭ‐ｚの割合（重量％）と溶解開始温度（Ｔｄ）および結晶の生長開始温度（Ｔｃ）との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to tetramethyl (1R, 1 ′S, 3R, 3 ′S, 4S, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate (hereinafter abbreviated as cis-DCTM-x). Tetramethyl (1R, 1′R, 3R, 3′R, 4S, 4 ′S) -dicyclohexyl-3,3′4,4′-tetracarboxylate (hereinafter referred to as cis-DCTM-y) And (1S, 1 ′S, 3S, 3 ′S, 4R, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (hereinafter referred to as cis-DCTM). -Sometimes abbreviated as -z).
[0002]
[Prior art]
Tetracarboxylic acid tetraesters are useful compounds as precursors for tetracarboxylic dianhydrides, which are raw materials for polyimide resins having excellent heat resistance.
It is well known that a benzene ring is reduced to a corresponding cyclohexane ring by hydrogen reduction. For example, synthetic communication, 25 , 2079 (1995), JP-A-10-36320, JP-A-11-189568, These are reported in JP-A-11-349535, JP-A-10-204002, and JP-B-8-30045.
[0003]
Hydrogen reduction of tetramethyl biphenyl-3,3'4,4'-tetracarboxylate (abbreviated as BPTM) has 6 asymmetric carbons in the product, thus allowing ²⁶ isomers It is. The hydrogen reduction of BPTM is also reported in JP-A-7-215912, JP-A-8-325196, JP-A-8-325201, and the like.
[0004]
These reports mention nothing about the isomers, only the mixture.
The object of the present invention is to efficiently separate a specific isomer from a large number of isomer mixtures.
[0005]
[Means for Solving the Invention]
This invention relates to tetramethyl (1R, 1 ′S, 3R, 3 ′S, 4S, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate and (1R, 1′R, 3R, 3'R, 4S, 4'S) -Dicyclohexyl-3,3'4,4'-tetracarboxylic acid tetramethyl and (1S, 1'S, 3S, 3'S, 4R, 4'R) -dicyclohexyl- When separating a mixture of three racemates with tetramethyl 3,3′4,4′-tetracarboxylate, a composition ratio and a crystal melting start temperature (Td) prepared in advance using pure isomers are used. ) And a graph showing the relationship between the crystal growth start temperature (Tc) and a) the range of the crystal melt start temperature (Td) and the growth start temperature (Tc) corresponding to each composition ratio of the isomer mixture A seed crystal is added at a temperature within the range, b) the temperature at which the crystal is precipitated (Tm Manipulating the at range of the following formula, wherein 10 ℃ ≦ (Tc-Tm) ≦ 25 ℃
And c) an efficient separation method of isomers characterized in that the precipitation time is 30 hours or less.
[0006]
The isomers of tetramethyl cis-dicyclohexyl-3,3′4,4′-tetracarboxylate of the present invention are preferably tetramethyl biphenyl-3,3′4,4′-tetracarboxylate (hereinafter referred to as BPTM). The product (DCTM) obtained by hydrogen reduction of the cis structure is recrystallized to preferentially separate cis structure isomers, which are further separated by preferential crystallization. It can be obtained by isolation.
A reaction formula in which the above BPTM is reduced to hydrogen to form DCTM is shown below.
[0007]
[Chemical 1]

[0008]
The BPTM used as the starting material is a method for producing a biphenyl compound by coupling dimethyl phthalate described in JP-B-60-33379, for example, in the presence of oxygen, a palladium salt and 1,10-phenanthroline or bipyridyl. Can be easily synthesized.
[0009]
A known method can be applied to the hydrogen reduction, and a normal organic solvent such as methanol, ethanol, butanol, ethyl acetate, or tetrahydrofuran can be used as the solvent. Although the usage-amount of a solvent will not be specified if it is the quantity which BPTM melt | dissolves sufficiently, it is 25-100 mL normally with respect to 10g BPTM.
[0010]
For the hydrogen reduction, Ru / C (carbon), Rh / C, Pd / C supported by 0.1 to 10% by weight, or an alumina support, silica support or the like can be used. A catalyst amount of 0.1 to 0.5 g is sufficient for 10 g of BPTM. As the reaction conditions, the reaction proceeds even at normal pressure, but in order to increase the speed, it is better to carry out under pressure, and 2 to 100 atm, preferably 10 to 50 atm is sufficient. The reaction temperature is 50 to 250 ° C, preferably 100 to 200 ° C. In order to complete the reaction, the reaction is carried out for 1 to 10 hours. The reaction is carried out until the absorption of hydrogen is completed, and is usually completed in about 5 hours at 100 ° C. Although it is not limited to the reaction method, it is good to supply additional hydrogen continuously.
[0011]
After removing the catalyst from the reaction solution by an operation such as filtration, a viscous solid remains as a product when the solvent is removed.
From this product mixture, tetramethyl cis-dicyclohexyl-3,3'4,4'-tetracarboxylate (cis-DCTM) was recrystallized in a suitable solvent or distilled under reduced pressure to give a specific fraction. It is obtained by collecting.
[0012]
As the solvent used for the recrystallization, a common organic solvent such as methanol, ethanol, butanol, ethyl acetate, tetrahydrofuran or the like can be used. The amount used is 200-1000 mL per 100 g of this product.
At this time, the cis isomer is preferentially precipitated. Capillary chromatography (CGC) showed a single peak, but high performance liquid chromatography (HPLC) showed three peaks when analyzed using a Chiralcel OD or Chiralpak AS column. Therefore, this cis isomer was resolved by the usual preferential crystallization method.
[0013]
As the solvent used for the separation, methanol, ethanol, butanol, ethyl acetate, tetrahydrofuran or the like can be used. Although there is no limitation in the amount used, pure isomers can be obtained by repeated crystallization at about 200 to 500 mL per 100 g.
The structure can ultimately be determined from X-ray analysis by growing single crystals.
[0014]
The chemical formula of 1R, 1 ′S, 3R, 3 ′S, 4S, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (cis-DCTM-x) Show.
[0015]
[Chemical 2]

[0016]
In this invention, (1R, 1′R, 3R, 3′R, 4S, 4 ′S) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (cis-DCTM-y) It can be expressed as a chemical formula.
[0017]
[Chemical 3]

[0018]
In this invention, (1S, 1 ′S, 3S, 3 ′S, 4R, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (cis-DCTM-z) It can be expressed as a chemical formula.
[0019]
[Formula 4]

[0020]
In separating the above three isomer mixtures, the composition ratio of cis-DCTM-x obtained by liquid chromatography (the composition ratio is determined from the area ratio), the melting start temperature (Td) of the x crystal, and the x crystal A graph showing the relationship between the growth start temperature (Tc) and the x crystal dissolution start temperature (Td) and x crystal corresponding to the respective composition ratios of the isomer mixture separately obtained by liquid chromatography. The seed x is added at a temperature within the range of the growth start temperature (Tc). If the seed crystal is added at a temperature higher than Td, the seed crystal diffuses into the solution, which is disadvantageous for crystallization.
When seed crystals are added at a temperature lower than Tc, the purity of the crystallized product decreases.
[0021]
Next, b) the temperature (Tm) for precipitating the crystals is controlled within the range of the following formula.
Formula: 10 ° C. ≦ (Tc−Tm) ≦ 25 ° C.
When this temperature difference is smaller than 10 ° C., the precipitation of crystals becomes slow. When this temperature difference is larger than 25 ° C., the purity of the crystal is lowered.
At this time, c) the deposition time is 30 hours or less, preferably 10 to 30 hours. Even if the time is shorter than 10 hours, crystals are precipitated, but the yield is low. If it is longer than 30 hours, the purity of the crystal is lowered.
[0022]
Subsequently, a graph showing the relationship between the composition ratio of cis-DCTM-yz and the dissolution start temperature (Td) of the yz crystal and the growth start temperature (Tc) of the yz crystal was prepared in advance, and separately obtained by liquid chromatography The seed crystal is added at a temperature within the range of the melting start temperature (Td) of the yz crystal and the growth starting temperature (Tc) of the yz crystal corresponding to the respective composition ratios of the isomer mixture obtained by (1).
Next, b) the temperature (Tm) for precipitating the crystals is controlled within the range of the following formula.
Formula: 10 ° C. ≦ (Tc−Tm) ≦ 25 ° C.
At this time, c) the deposition time is 30 hours or less, preferably 10 to 30 hours.
[0023]
According to the separation method of the present invention, each of cis-DCTM-x and cis-DCTM-yz (racemate) can be obtained with high purity and high efficiency.
[0024]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
In the following examples, high performance liquid chromatography is Shimadzu SCL-10A, column: Chirapak AS (Daicel Chemical Industries) 0.46 cmφ, 25 cm, 20 ° C., EtOH / n-hexane (10/90), 0.5 mL / min. Measured with
[0025]
Measurement of crystal dissolution start temperature and crystal growth start temperature In a 100 mL test tube, pure x component and yz component were prepared in a specific weight ratio (total amount 6 g), and 12 mL of THF was added thereto to make a homogeneous solution once. Sealed. This test tube was placed in a bath with a temperature controller, seed crystal x was added, and the melting start temperature of seed crystal x and the growth start temperature of seed crystal x were measured visually. A graph showing the relationship between the ratio (wt%) of cis-DCTM-x obtained from this result, the dissolution start temperature (Td), and the crystal growth start temperature (Tc) is shown in FIG. 1 (x component basis). Similarly, seed crystal yz was added, and the dissolution start temperature of seed crystal yz and the growth start temperature of seed crystal yz were measured visually. A graph showing the relationship between the ratio (wt%) of cis-DCTM-yz obtained from this result, the dissolution start temperature (Td), and the crystal growth start temperature (Tc) is shown in FIG. 2 (based on the yz component). .
[0026]
Example 1
A 500 mL rotary autoclave is charged with 100 g of BPTM, 2.5 g of 5% Rh / C, and 200 mL of tetrahydrofuran, and at a constant pressure of 30 kg / cm ² of hydrogen at 100 ° C. and 300 rpm for 5.5 hours. Heated (absorption of hydrogen was completed in about 5 hours). After the reaction solution was filtered using No5c filter paper, tetrahydrofuran was distilled off to obtain 101.8 g (yield 99%) of a viscous product. This was dissolved in 400 mL of methanol and crystallized to obtain 72 g of cis-DCTM. From the analysis of high performance liquid chromatography, it was cis-DCTM (x / y / z) = (50/25/25). The same operation was performed for 4 batches to isolate cis-DCTM crystals.
[0027]
Of these, 200 g of cis-DCTM crystals (cis-DCTM-x / yz = 50/50) were collected and dissolved in 400 mL of tetrahydrofuran. After bringing the solution to 28 ° C., a small amount of seed crystal x was added to the above solution, and this was left to stand at 10 ° C. for 20 hours and held. 29.2 g of crystals (A) were separated, and the ratio of the x component was 97.3%. The isomer composition of the filtrate (L) was x / yz = 45/55. A was further dissolved in 58 mL of tetrahydrofuran, seed crystal x was added at 48 ° C., and the mixture was left to stand at 25 ° C. for 20 hours. 18.8 g of crystals (B) were separated, and the ratio of the x component was 100%.
[0028]
After the solution of L was evaporated to a crystal / THF ratio of 1/2 (181 g / 362 mL) and the solution was brought to 25 ° C., a small amount of seed crystal yz was added to the above solution, which was allowed to stand at 5 ° C. for 20 hours. Set and held. 22.8 g of crystals (M) were separated, and the ratio of the yz component was 96.0%. M was further dissolved in 46 mL of tetrahydrofuran, seed crystal yz was added at 40 ° C., and the mixture was allowed to stand at 18 ° C. for 20 hours and held. 14.0 g of crystals (N) were separated, and the ratio of the yz component was 100%.
[0029]
Example 2
200 g of cis-DCTM crystals (cis-DCTM-x / yz = 50/50) obtained by the same operation as in Example 1 was collected and dissolved in 400 mL of tetrahydrofuran. After bringing the solution to 28 ° C., a small amount of seed crystal x was added to the above solution, and this was left to stand at 5 ° C. for 20 hours and held. 37.3 g of crystals (A) were separated, and the ratio of the x component was 96.3%. The isomer composition of the filtrate (L) was x / yz = 39/61. A was further dissolved in 75 mL of tetrahydrofuran, seed crystal x was added at 47 ° C., and the mixture was allowed to stand at 27 ° C. for 20 hours and held. 23.3 g of crystals (B) were separated, and the ratio of the x component was 100%.
[0030]
After evaporating the solution of L to a crystal / THF ratio of 1/2 (162 g / 324 mL) and bringing the solution to 30 ° C., a small amount of seed crystal yz was added to the solution, and this was allowed to stand at 3 ° C. for 20 hours. Set and held. 31.6 g of crystals (M) were separated, and the ratio of the yz component was 97.5%. M was further dissolved in 63 mL of tetrahydrofuran, seed crystal yz was added at 40 ° C., and the mixture was allowed to stand at 17 ° C. for 20 hours and held. 20.4 g of crystals (N) were separated, and the ratio of the yz component was 100%.
[0031]
【The invention's effect】
According to the present invention, (1R, 1 ′S, 3R, 3 ′S, 4S, 4′R) -dicyclohexyl-3,3, which is useful as a precursor of tetracarboxylic dianhydride, which is a raw material for polyimide resins, etc. High purity product of tetramethyl '4,4'-tetracarboxylate (cis-DCTM-x) and (1R, 1'R, 3R, 3'R, 4S, 4'S) -dicyclohexyl-3,3' Tetramethyl 4,4'-tetracarboxylate (cis-DCTM-y) and (1S, 1'S, 3S, 3'S, 4R, 4'R) -dicyclohexyl-3,3'4,4'-tetra A racemic high-purity product with tetramethyl carboxylate (cis-DCTM-z) can be separated and obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the ratio (% by weight) of cis-DCTM-x, the dissolution start temperature (Td), and the crystal growth start temperature (Tc).
FIG. 2 is a graph showing the relationship between the ratio (% by weight) of cis-DCTM-y and cis-DCTM-z, the dissolution start temperature (Td), and the crystal growth start temperature (Tc).

Claims (1)

In tetrahydrofuran (1R, 1'S, 3R, 3'S, 4S, 4'R) - dicyclohexyl -3,3'4,4'- tetracarboxylic acid tetramethyl (hereinafter, abbreviated as cis-DCTM-x) And (1R, 1′R, 3R, 3′R, 4S, 4 ′S) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (hereinafter abbreviated as cis-DCTM-y) (1S, 1 ′S, 3S, 3 ′S, 4R, 4′R) -dicyclohexyl-3,3′4,4′-tetracarboxylate tetramethyl (hereinafter abbreviated as cis-DCTM-z) This is a separation method in which a crystal composed of a cis-DCTM-x component or a crystal composed of a component of cis-DCTM-y and cis-DCTM-z is crystallized and separated from a mixed solution in which three racemic mixtures are dissolved. Te, tetrahydrofuran After previously measured relationship between dissolution starting temperature (Td) and the crystal growth starting temperature of crystal and compositional ratio using the isomer of pure (Tc) for, a) an isomeric mixture of the mixed solution The cis-DCTM-x component, or cis-DCTM-y and cis-DCTM-z , at a temperature within the range of the melting start temperature (Td) and the growth start temperature (Tc) corresponding to the respective composition ratios of Adding a seed crystal composed of the following components : b) operating the temperature (Tm) for precipitating the crystal within the range of the following formula, formula 10 ° C. ≦ (Tc−Tm) ≦ 25 ° C.
And c) A method for efficiently separating crystals comprising a cis-DCTM-x component or crystals comprising a component of cis-DCTM-y and cis-DCTM-z, wherein the precipitation time is 30 hours or less.

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