JPH1036350A - Purification of 4-hydroxypiperidine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying 4-hyroxypiperidine to a high purity according to an industrially easy method. SOLUTION: Crude 4-hydroxypiperidine is recrystallized by using an organic solvent, e.g. acetone, tetrahydrofuran or methyl ethyl ketone to afford a high- purity columnar or needlelike crystalline substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying 4-hydroxypiperidine. 4-Hydroxypiperidine is a compound useful as a raw material for medicines and agricultural chemicals, and is used as a raw material for propericiazine, for example, which is known as a psychotropic drug.

[0002]

2. Description of the Related Art Conventionally, as a method for purifying 4-hydroxypiperidine, a method of purifying crude 4-hydroxypiperidine by distillation, a method of converting crude 4-hydroxypiperidine into an addition salt of hydrochloric acid, and then isolating 4-hydroxypiperidine. Methods for purification are known.

According to the method, 4-hydroxypiperidine has a sublimability and is a solid having a melting point of 89 to 92 ° C.
Distillation operation is difficult. In addition, since the compound has hygroscopicity, it is necessary to shut off moisture even when pulverized after distillation to obtain a powder, the operation is complicated, and a special apparatus is required in the method of purification by distillation. There is a problem.

According to the method of (1), crude 4-hydroxypiperidine is recrystallized as a stable acid addition salt in an alcoholic solvent such as methanol, ethanol or isopropanol, and then filtered and dried to obtain 4-hydroxypiperidine hydrochloride. However, in order to isolate 4-hydroxypiperidine from the compound, a complicated operation such as neutralization with an aqueous alkali solution, extraction with an organic solvent, washing of the organic layer with water and drying, followed by distilling off or distilling off the solvent, is required. . The method (1) also has the same problem as the method in which the pulverization is finally performed.

[0005] As described above, the technology for purifying 4-hydroxypiperidine has not been industrially established.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide 4-
An object of the present invention is to provide a method for purifying hydroxypiperidine with high purity by an industrially easy method.

[0007]

The present inventors have made intensive studies to solve the above problems, and as a result, recrystallized crude 4-hydroxypiperidine using an organic solvent to obtain high-purity crystals. The present inventors have found a method for obtaining the above compound, and have completed the present invention.

The organic solvent used for the recrystallization is not particularly limited as long as it is an organic solvent capable of appropriately dissolving 4-hydroxypiperidine, and examples thereof include ketones such as acetone and methyl ethyl ketone, tetrahydrofuran (THF), dimethoxymethane, Ethers such as dimethoxyethane,
Esters such as methyl acetate and ethyl acetate (first solvent)
And the like. These may be used alone or in combination of two or more. When using hydrocarbons such as hexane, cyclohexane, methylcyclohexane, and toluene, which are poor solvents, they may be used in combination with the first solvent. Alcohols such as methanol, ethanol and isopropanol, which are good solvents, are not suitable for use alone, but can be used in combination with poor solvents. A preferred solvent when used alone is low boiling acetone which tends to dry the crystals of 4-hydroxypiperidine.

When the organic solvent is used alone, it is usually used in an amount of 2 to 15 times the weight of 4-hydroxypiperidine, but the amount of the solvent may be appropriately adjusted depending on the solubility of the solvent in the compound. The recrystallization is performed by dissolving at a temperature around the boiling point of the organic solvent to be used and then slowly cooling to crystallize.

[0010] It is also effective for purification to add activated carbon or activated clay at the time of recrystallization and to perform a decolorization treatment in a state where 4-hydroxypiperidine is dissolved when heated.

The 4-hydroxypiperidine obtained by recrystallization can be filtered and dried according to a conventional method to obtain a final product.

[0012]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples.
The present invention is not limited thereby.

Example 1 In a 5 L four-necked flask equipped with a stirrer, a thermometer, and a condenser, 930.3 g of crude 4-hydroxypiperidine having a purity of 93.6% by gac chromatography (GC) and 1860.6 g of acetone were charged. After heating and dissolving at 60 ° C. and treating it with 9.3 g of activated carbon while hot, recrystallization was performed by cooling with ice water, and the crystals were collected by filtration and dried (70 ° C./15 Torr, 4 ° C.).
After that, 874.1 g of 4-hydroxypiperidine as white columnar crystals was obtained. GC purity was 99.9%. 0.01% was residual solvent.

Example 2 A 500 mL four-necked flask equipped with a stirrer, a thermometer and a condenser was charged with 69.5 g of crude 4-hydroxypiperidine having a GC purity of 98.6% and 208.5 g of THF.
After heating and dissolving the mixture at 0 ° C., the mixture was cooled with ice water to perform recrystallization. The crystals were collected by filtration and dried (60 ° C./5 Torr, 3 hours) to give 4-hydroxypiperidine 6 as white needle crystals.
5.9 g were obtained. GC purity was 99.8%. 0.
2% was residual solvent.

Example 3 69.4 g of crude 4-hydroxypiperidine having a GC purity of 98.6% and 1041.0 g of dimethoxymethane were charged into a 2 L four-necked flask equipped with a stirrer, a thermometer, and a cooler. After heating and dissolving, the mixture is cooled with ice water to perform recrystallization, and the crystals are collected by filtration and dried (60 to 70 ° C / 25 to 35
(Torr, 5 hours) to obtain 51.9 g of 4-hydroxypiperidine as white needle crystals. GC purity is 9
9.9%. 0.1% was residual solvent.

Example 4 In a 500 mL four-necked flask equipped with a stirrer, a thermometer and a condenser, 62.1 g of crude 4-hydroxypiperidine having a GC purity of 96.9%, 1,2-dimethoxyethane 240.
0 g was charged and dissolved at 87 ° C. by heating.
After the treatment in Step 62, recrystallization was performed by cooling with ice water, and the crystals were collected by filtration and dried (60 ° C./2 Torr, 4 hours) to give 4-hydroxypiperidine as white needle crystals.
0 g was obtained. GC purity was 99.7%. 0.3%
Was the residual solvent.

Example 5 A 1L four-necked flask equipped with a stirrer, a thermometer and a condenser was charged with 128.5 g of crude 4-hydroxypiperidine having a GC purity of 98.1% and 400.0 g of ethyl acetate.
After heating and melting at 3 ° C, it was cooled with iced water and recrystallized.
The crystals were collected by filtration and dried (40 ° C./2 Torr, 4 hours) to obtain 120.6 g of 4-hydroxypiperidine as white fine needle crystals. GC purity was 99.2%. 0.8% was residual solvent.

Example 6 10.0 g of 4-hydroxypiperidine having a GC purity of 98.5%, 27.0 g of toluene, and 4.8 g of isopropanol were charged into a 100 mL four-necked flask equipped with a stirrer, a thermometer, and a cooler. After heating and melting at 101 ° C., the mixture was cooled with ice water to perform recrystallization, and the crystals were collected by filtration and dried (40 to 7).
At 0 ° C./2 Torr for 3 hours), 8.0 g of 4-hydroxypiperidine as fine white needle-like crystals was obtained. GC
Purity was 99.8%. 0.2% was residual solvent.

[0019]

According to the present invention, 4-hydroxypiperidine, which is useful as a raw material for medicines and agricultural chemicals, can be purified to a high purity by an industrially easy method.

Claims (1)

[Claims] 1. A method for purifying 4-hydroxypiperidine, comprising recrystallizing crude 4-hydroxypiperidine using an organic solvent to obtain a high-purity columnar or needle-like crystal.