JP2001518465A - Purification method of 4-aminopiperidine - Google Patents

Abstract

  (57) [Summary] A process for purifying the 2,2,6,6-tetrasubstituted 4-aminopiperidine prepared from the corresponding piperidin-4-one by subsequent distillation is described in US Pat. Reacting the piperidine with hydrogen in the presence of a hydrogenation catalyst and a dehydrogenation catalyst to separate 4-aminopiperidine from the reaction mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for the subsequent purification of 2,2,6,6-tetrasubstituted 4-aminopiperidines prepared from the corresponding piperidin-4-ones by distillation.

In particular, the present invention provides compounds of formula II

[0003]

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Wherein R ¹ -R ⁴ are C ₁ -C ₆ alkyl and R ¹ and R ² and / or R ³ and R ⁴ together are CH 2 -C 5 ₂ strands produced from the corresponding piperidin-4-one formed is] a, formula I

[0005]

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A process for purifying 4-aminopiperidine of the formula wherein the group R is as indicated above by subsequent distillation.

[0007] 4-Aminopiperidine, indicated as sterically hindered by 2,2,6,6-substitution, for example tetraalkyl substitution, is used for various applications. In particular, this compound is used as an intermediate in the preparation of UV stabilizers for synthetic polymers (for example: R. Gaechter, H. Mueller (editor): Taschenbuch der kunststoffadditive,
Carl Hanser Verlag, Munich, 1979; F. Gugumus, Polym, Degrad. Stabil. 4
4 (1994), 299-322) and as chain regulators and stabilizers in the production of polyamides (see, for example, WO 9528443, DE-A-441 177).

The sterically hindered 4-aminopiperidines not only have high chemical purity, but also have no or little intrinsic color and do not fade over a storage period of several months Is particularly important. This applies in particular when 4-aminopiperidine is used for the preparation of stabilizers or as such as additives, since the product quality of the compounds and thus the stabilized This is because the quality of the obtained polymers obviously depends on the chemical purity, in particular on the quality of the color.

[0009] Sterically hindered 4-aminopiperidines are generally produced industrially from dialkyl ketones, such as acetone or acetone derivatives. Piperidine I is converted to a compound by catalytic ring closure in the presence of ammonia and hydrogen.

[0010]

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May be obtained in a single step from (DE-A-2421750) or by amino hydrogenation, for example catalytically with piperidin-4-one II

[0012]

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May be obtained in one or two steps (eg DE-A-352 538)
7, DE-A-2040975, DE-A-2349962, DE-A-262
1870, EP-A-33529, EP-A-42119, EP-A-3032
79, EP-A-410970, EP-A-611137, EP-A-6235
85 and DE-A-4210311). Industrially produced sterically hindered 4-aminopiperidines are generally purified by distillation (eg, EP
-A-33529).

However, the unpleasant amounts of color-producing substances are still present or are present in 4-amino-2,2,6,6-tetraalkylpiperidines produced using conventional methods. Formed after hours.

According to DE-A-1955558, EP-A-28555, US Pat. No. 3,819,710 and JP 01160947 (Chem. Abstr. 111: 232081r), compounds which form a color in certain amino alcohols, in this case this compound Can be formed during the production of amino alcohols from ethylene oxide and the appropriate amines and can be converted to compounds that form less color by catalytic hydrogenation.

JP 0625410 (Chem. Abstr. 121: 56988n), JP-OS 48-
52708 (Chem. Abstr. 80: 36697y), JP 05345821 (Chem. Abs.
tr. 120: 272327t), US Pat. No. 5,362,914 and EP-A-262562 disclose that bleaching in certain polyamines can be reduced by treatment with hydrogen in the presence of a hydrogenation catalyst. .

DE-A-2205958 discloses that tertiary amines obtained by reacting primary alcohols with ammonia are purified by hydrogenating impurities before the final distillation of the tertiary amines. A method for doing so is disclosed.

The above compounds are of a different type than the sterically hindered 4-amino-piperidine substances of the present invention. In addition, the source of the color-forming impurities in the compounds lies in the particular preparation methods and the starting materials used in each case.

JP-OS 02-31457 describes purifying 2,2,6,6-tetraalkyl-4-piperidinone by treatment with hydrogen in the presence of a hydrogenation catalyst. . According to the example described in this specification, the process product (triacetoneamine, TAA), after storage at 60 ° C. for only one week,
Extremely color instability so as to have significantly poorer color quality than the starting material.

The development of a process for the preparation of chemically pure sterically hindered 4-aminopiperidines with low bleaching required a completely different route: DD-A-266799 requires acetone / 4-amino-2,2 in a solution of water
, 6,6-reaction with tetramethylpiperidine and CO _2, separating off the precipitate, washing with acetone, the purification of the product by subsequent pyrolysis and distillation is taught.

SU 1811527 describes a different purification method for sterically hindered 4-aminopiperidine I. In this method, the contaminated crude product is dissolved in an aprotic solvent and reacted with ethylene glycol, the reaction product is isolated, 4-aminopiperidine is freely adjusted using an aqueous alkaline solution, and After the aqueous phase has been removed, fractional distillation is carried out.

[0022] Both methods are extremely complicated and costly.

[0023] Finally, the earlier German Patent 196 22 6.99.9 states that in a first stage high-boiling substances and possibly water are removed from crude piperidine by distillation, and in a second stage the production of the first stage The crude 4-aminopiperidine I is purified by adding 0.01 to 5% by weight, based on the product, of a reducing agent, for example sodium borohydride, and in a third step isolating the piperidine I by distillation. Distillation methods are described.

The object of the present invention is to provide an inexpensive method which is simple to carry out and which makes it possible, for example, to obtain colorless, color-stable and highly pure sterically hindered 4-aminopiperidines of the formula I It is to be. This means a product in which the very unique coloration of the product is maintained over a long period of time, while having a low by-product content and free of stabilizing aids. For reference, 4-aminopiperidine I as "colorless" contains minimal fading, i.e. a color number of at most 40 APHA (DIN-ISO
6271).

The purpose of this is to react the distilled 2,2,6,6-tetrasubstituted 4-aminopiperidine with hydrogen in the presence of a hydrogenation or dehydrogenation catalyst, and then to react 4% again from the reaction mixture. -Achieved by a process for purifying a 2,2,6,6-tetrasubstituted 4-aminopiperidine prepared from the corresponding piperidin-4-one by subsequent distillation, characterized in that the aminopiperidine is separated. Was found. In sterically hindered 4-aminopiperidine I, the radicals R ¹ , R ² , R ³ and R ⁴ are, independently of one another, preferably C ₁ -C ₃ alkyl, for example ethyl or methyl, Especially methyl.

According to the invention, the pure but bleaching and / or bleaching, for example of formula I, obtained by known processes by reaction of the corresponding piperidin-4-ones, for example aminohydrogenation and subsequent fractional rectification, Alternatively, the color-labile 4-aminopiperidine is reacted with hydrogen at, for example, 20-200 ° C. in the presence of a hydrogenation catalyst. Higher temperatures are also possible. Preferably, the reaction temperature is in the range of 50 to 150 ° C.

The reaction of 4-aminopiperidine with hydrogen can be carried out under atmospheric pressure or preferably under superatmospheric pressure.
For example, it may be performed at 0.1 to 50 MPa. Higher pressures are also possible. Preferably, the reaction pressure is 1 to 30 MPa, especially 1 to 20 MPa.

The reaction of 4-aminopiperidine with hydrogen may be carried out in the presence of a solvent or solvent mixture which is inert under the reaction conditions, or preferably in the absence of a solvent. If a solvent is used, for example tetrahydrofuran, dioxane, 1,2-dimethoxyethane, methanol or ethanol, the reaction conditions are chosen such that the solvent is present in the reaction mixture in liquid form.

There are no restrictions as to the hydrogenation catalyst that may be used. Also, dehydrogenation catalysts can be used.

[0030] Suitable hydrogenation catalysts are, for example, those containing copper, silver, gold, iron, cobalt, nickel, ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum, chromium, molybdenum or mixtures thereof. .

The hydrogenation catalyst used, for example, when sodium tris (triphenylphosphine) rhodium is used, is homogeneously dissolved in 4-aminopiperidine or in a mixture of 4-aminopiperidine and a solvent. Or particularly preferably it may be present in undissolved form, ie in a heterogeneous manner.

Suitable heterogeneous catalysts are unsupported catalysts, such as Raney nickel or Raney cobalt, wherein the Raney cobalt is present as a suspension in the reaction mixture or preferably is fixed in the reactor Supported catalyst arranged as a bed. In the case of a supported catalyst, suitable support materials for the catalytically active metal or metal compound include, for example, carbon, aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide, silicon carbide, zeolite or mixtures thereof. It is.

Examples which may be mentioned are supported catalysts containing copper and / or cobalt and / or nickel and aluminum oxide and / or zirconium dioxide.

For example, the following composition: 76% by weight of Al calculated as Al ₂ O ₃ , Cu 4 calculated as CuO
% By mass, 10% by mass of Co calculated as CoO and 10% by mass of Ni calculated as NiO (as described in DE-A-1953263) or 31.5% by mass of Zr calculated as ZrO _2, as NiO Two supported catalysts with calculated Ni 50% by weight, Cu 17% by weight calculated as CuO and Mo 1.5% by weight calculated as MoO ₃ (as described in EP-A-696572) were used. You may.

The required residence time of the 4-aminopiperidine on the catalyst depends, inter alia, on the degree of discoloration of the distilled 4-aminopiperidine and the desired decolorization of the piperidine and / or
Or it is determined by color stability. In general, the longer the residence time, the greater the degree of fading of the 4-aminopiperidine used in the process of the invention,
And the quality of the color required for the product is also high. Depending on the reaction conditions chosen,
Generally, a residence time of 10 minutes to a few hours is sufficient.

The process steps of the invention may be carried out continuously, for example in a tubular reactor, stirred vessel or cascade of stirred vessels, or batchwise, for example in stirred vessels.

After carrying out the process according to the invention, the 4-aminopiperidine is separated from the hydrogenation catalyst and any solvents used.

The hydrogenation catalyst dissolved in the reaction product is separated off by distillation, in which case any solvent used and 4-aminopiperidine are continuously removed from the top in a conventional manner.

[0039] The hydrogenation catalyst used in the suspension is separated off by decantation and / or filtration. The reaction product may be subsequently distilled, which is required in any case where a solvent is used.

If a hydrogenation catalyst arranged as a fixed bed is used, the reaction product is advantageously filtered to remove any scavenged catalyst present. The reaction product may be subsequently distilled, in which case this distillation is required in any case where a solvent is used.

According to the process of the present invention, in a simple and inexpensive manner, pure sterically hindered 4-amino acids which do not actually have an inherent color and retain color stability during storage Piperidine is formed and therefore no addition of stabilizer is necessary.

EXAMPLES The color of sterically hindered 4-aminopiperidines was determined by measuring the APHA color number according to DIN-ISO6271. In all cases, TAD
Sample storage was performed under comparable conditions (room temperature, in the dark).

Example 1 (Comparative Example): 2,2,6,6-tetramethylpiperidin-4-one (triacetoneamine,
TAA) [GC purity: 99%; APHA color number: about 370 (measured as a 1% strength solution in ethanol)] at 165 ° C., 12 MPa H ₂ , calculated as Al ₂ O _{3 at} 76% by mass Al , 4% by mass of Cu calculated as CuO, CoO
Obtained by aminohydrogenation in the presence of a heterogeneous catalyst (as described in DE-A-1953263) containing 10% by weight of Co calculated as Ni and 10% by weight of Ni calculated as NiO. the following composition (weight%) of 4-amino-2,2,6,6-tetramethylpiperidine _{(triacetonediamine, TAD) 85.6% H 2 O} 9.0% NH 3 0.7% 4 Hydroxy-2,2,6,6-tetramethylpiperidine 1.4% (triacetone amino alcohol, TAA-ol) 1.632 kg of a crude synthetic product containing 3.3% of a by-product containing a high-boiling substance. , Double-wall heap
In a distillation apparatus having a 2.0 l still with a 3 mm V2A helical wire, a 70 cm reflective glass column (internal column diameter 3.5 cm) and a column head with liquid distributor Rectified.

As the main fraction, 1.191 kg of a slightly yellowish TAD having a purity of 99.9% (according to GC) were obtained under a pressure of 40-42 hPa and a top temperature of 99-102 ° C. The TAD obtained gradually became yellowish during the following days, ie not color stable.

Storage time in days below APHA color number 5 145 70 268 Example 2: Obtained as described in Example 1 in a 300 ml autoclave equipped with a stirrer and a basket insert. was yellowish TAD (purity ≧ 99.9% by GC; APHA color number: 72) of about 70 g (0.45 mol), is present as a fixed bed in the mounting cage, which is calculated as Al ₂ O ₃ 76% by mass of Al, 4% by mass of Cu calculated as CuO, Co calculated as CoO
Treated with hydrogen for 6 hours at 90 ° C. under a pressure of 10 MPa in the presence of a heterogeneous catalyst (4 mm extrudate) containing 10% by weight of Ni, calculated as NiO, 10% by weight.

Next, the reaction product was filtered. The purity of the colorless TAD obtained was 9 according to GC.
9.9%. The APHA color number of the TAD was less than 1 after a storage period of 50 days. Even after a storage period of 147 days, the TAD appeared visually colorless, ie, the APHA color number was less than 10.

Example 3 The experiment was carried out as in Example 2, but with 5 g of Raney nickel as heterogeneous catalyst (suspended) and, after filtration, a purity of 99.9% and 5% by GC.
A colorless TAD having an APHA color number of 17 after a storage period of 0 days was obtained. After a storage time of 148 days, the APHA color number was 23.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AU, BG, BR, BY, CA, CN, CZ, GE, HU, ID, IL, JP, KR , KZ, LT, LV, MK, MX, NO, NZ, PL, RO, RU, SG, SI, SK, TR, UA, US (72) Inventor Tom Witzel Ludwigshafen Fen Creamhildstrasse Germany 34 (72) Inventor Wolfgang Siegel Limburgerhof Goethe, Germany Yutorase 34-based F-term (reference) 4C054 AA02 BB03 CC01 DD03 DD08 EE01 FF30

Claims (9)

[Claims] 1. 2,2,6 prepared from the corresponding piperidin-4-one
In a process for purifying a 6-tetrasubstituted 4-aminopiperidine by subsequent distillation, the distilled 2,2,6,6-tetrasubstituted 4-aminopiperidine is treated in the presence of a hydrogenation catalyst or a dehydrogenation catalyst. A method for purifying 2,2,6,6-tetra-substituted 4-aminopiperidine, which comprises reacting with hydrogen and separating 4-aminopiperidine from the reaction mixture. 2. A compound of formula II Wherein R ¹ -R ⁴ are C ₁ -C ₆ alkyl and R ¹ and R ² and / or R ³ and R ⁴ together form a CH ₂ chain having ₂ to 5 carbon atoms. Formula I) prepared from the corresponding piperidin-4-one of the formula I The process according to claim 1 for purifying 4-amino-piperidine of the formula wherein the group R is as indicated above. 3. A process according to claim 1 for purifying 4-amino-piperidines of formula I according to claim ² , wherein R ¹ , R ² , R ³ and R ⁴ are methyl. 4. The reaction according to claim 1, wherein the reaction with hydrogen is carried out at 20 to 200 ° C.
The method according to any one of the preceding claims. 5. The process according to claim 1, wherein the reaction is carried out under a pressure of 1 to 30 MPa.
The method according to any one of the preceding claims. 6. The process as claimed in claim 1, wherein the reaction is carried out in the absence of a solvent. 7. The method according to claim 1, wherein the hydrogenation catalyst contains copper, silver, gold, iron, cobalt, nickel, ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum, chromium, molybdenum or a mixture thereof. The method according to any one of claims 1 to 6. 8. The process as claimed in claim 1, wherein the hydrogenation catalyst used is a supported catalyst. 9. The hydrogenation catalyst used is nickel and / or copper and / or
9. The process according to claim 1, which is a supported catalyst containing cobalt and aluminum oxide and / or zirconium dioxide.