Method for preparing a piperidine compound

Abstract

The present invention provides a method for preparing a compound of formula (1) (wherein R1 and R2 are each independently a C1-C8 alkyl), comprising the steps of: 8 mPa~200×10 8 The method relates to a method comprising the step of reacting a compound of formula (2) with a formaldehyde source at a hydrogen pressure of 1000 mPa. TIFF2023506071000015.tif79157

Description

Technical Field

[0001] The present invention relates to a method for preparing an N-methylated piperidine-containing compound of formula (1) given below by reacting it with an NH piperidine-containing compound of the corresponding formula (2) and a formaldehyde source in the presence of a palladium or platinum catalyst at a hydrogen pressure of 5×10 8 mPa to 200×10 8 mPa.

Background Art

[0002] The compound of formula (1) is used in the preparation of hindered amine light stabilizers (so-called HALS), which are used for the stabilization of plastics against degradation induced by light, heat or oxidation. Examples of such HALS are those of formula (3) and formula (5) given below.

Summary of the Invention

Problems to be Solved by the Invention

[0003] A general method for the N-methylation of piperidine compounds is disclosed in EP-A-729 947, according to which the N-methylation is carried out using formaldehyde and formic acid (Eschweiler-Clarke reaction). Usually, an excess of formic acid is used, so after the reaction, a neutralization step with a base follows, and the method results in the generation of a certain amount of waste.

[0004] Methods for N-alkylating amine derivatives by reductive amination with a transition metal catalyst using hydrogen and an aldehyde source are generally known, but when applied to compounds containing halogen-triazine, such as the compound of formula (2), a dehalogenation reaction is expected to occur.

Means for Solving the Problems

[0005] Here, according to the method of the present invention, it has been found that the corresponding dehalogenation reaction can be minimized, and the compound of formula (1) can be prepared in a high yield. The catalyst can be easily recovered, and the generation of waste is minimized.

[0006] Therefore, the present invention relates to a method for preparing a compound of the formula

[0007] [Chemical Formula] (wherein R1 and R2 are independently of each other C1-C8 alkyl) comprising the step of reacting a compound of in the presence of a palladium or platinum catalyst at a hydrogen pressure of 5×10 8 mPa to 200×10 8 mPa with a compound of the formula

[0008] [Chemical Formula] and a formaldehyde source. MODE FOR CARRYING OUT THE INVENTION

[0009] R1 and R2 are preferably, independently of each other, C1-C4 alkyl, especially butyl. n-Butyl is very preferred.

[0010] The term formaldehyde source is used for a compound that releases formaldehyde for further reaction.

[0011] Examples of formaldehyde sources are paraformaldehyde, formaldehyde and methanol. Paraformaldehyde and formaldehyde, especially paraformaldehyde, are preferred. Formaldehyde is preferably used in the form of formalin (an aqueous solution of formaldehyde, for example, the corresponding 30-40 wt% solution optionally stabilized with methanol).

[0012] Generally, the molar ratio of the formaldehyde source to the compound of formula (2) is from 1:1 to 10:1, especially from 1:1 to 5:1, more preferably from 1:1 to 3:1.

[0013] 10×10 8 mPa to 150×10 8 mPa, especially 20×10 8 mPa to 150×10 8 mPa of hydrogen pressure is preferred. According to one embodiment of the present invention, the hydrogen pressure is 10×10 8 mPa to 50×10 8 mPa, especially 20×10 8 mPa to 50×10 8 mPa.

[0014] Preferably, the method is carried out at a temperature of 50 to 180°C, especially 80 to 150°C. A temperature of 90 to 140°C is highly preferred.

[0015] The method can be carried out with or without a solvent. Generally, the method is carried out in the presence of a solvent, such as water or an organic solvent. Examples of organic solvents are aliphatic solvents, aromatic solvents and alcohols, such as pentane, hexane, heptane, octane, decane, cyclopentane, cyclohexane, methylcyclohexane, petroleum ether, benzene, toluene, xylene, ethylbenzene, cumene, bromobenzene, chlorobenzene, dichlorobenzene, furan, methanol, ethanol, n-propanol and isopropanol, preferably hexane, methanol, toluene and xylene.

[0016] As the solvent, water, hexane, methanol, toluene and xylene are preferred, preferably methanol, toluene and xylene. Toluene and xylene, especially xylene, are highly preferred.

[0017] The amount of solvent that can be used in the method of the present invention is, for example, 10 to 95% by weight, especially 20 to 90% by weight, more preferably 40 to 90% by weight, based on the weight of the reaction mixture. An amount of 40 to 90% by weight is highly preferred.

[0018] It is preferable to use a supported palladium (Pd) catalyst or a platinum (Pt) catalyst. These usually contain elemental Pd or Pt supported on a suitable carrier. Any known carrier material, such as carbon, calcium carbonate, aluminum oxide, titanium dioxide, or natural or synthetic zeolite, especially carbon, can be used.

[0019] A palladium catalyst or a platinum catalyst supported on a carbon carrier is preferred.

[0020] Generally, according to one embodiment of the present invention, a palladium catalyst, for example, a palladium catalyst supported on a carbon carrier, is used. Similarly, according to a further embodiment of the present invention, a platinum catalyst, for example, a platinum catalyst supported on a carbon carrier, is used.

[0021] The amount of palladium or platinum in such supported catalysts is, for example, 0.1 to 20% by weight, especially 1 to 20% by weight, based on the weight of the supported catalyst. An amount of 2 to 15% by weight is highly preferred.

[0022] The amount of the catalyst used in the method of the present invention is, for example, 0.5 to 20% by weight, especially 2 to 15% by weight, based on the weight of the compound of formula (2).

[0023] The method according to the present invention can be carried out continuously or discontinuously, for example, in a batch mode.

[0024] The reaction time is determined according to the reaction conditions and may be, for example, 2 to 40 hours, especially 6 to 40 hours. The preferred upper limit is 24 hours, more preferably 12 hours.

[0025] According to a preferred embodiment of the present invention, in the presence of a catalyst of palladium or platinum supported on a carbon carrier and a solvent, such as water, methanol, toluene or xylene, 10×10 8 mPa~150×10 8At a hydrogen pressure of mPa and a temperature of 80 to 150 °C, the compound of formula (2) (wherein R1 and R2 are n-butyl) is reacted with paraformaldehyde or formaldehyde.

[0026] For such embodiments, the definitions and preferences given above shall apply.

[0027] The compound of formula (2) is known and can be prepared, for example, according to EP 455 588, Example 1A).

[0028] The mixture obtained after the preparation of the compound of formula (1) can usually be used directly for the further conversion of the compound of formula (1) after separation of the catalyst. No further purification steps are necessary.

[0029] The compound of formula (1) prepared according to the method of the present invention is a HALS, for example, the following formulas (3) and (5)

[0030]

Chemical formula

[0031]

Chemical formula

[0032]

Chemical formula

[0033] The compound of formula (3), namely Chimassorb® 119, is commercially available. The compound of formula (1) is prepared according to the method of the present invention, and such a compound of formula (1) and the formula

[0034]

Chemical formula

[0035] The reaction is preferably carried out at a temperature of 50 - 200 °C, preferably 100 - 200 °C, in an aromatic hydrocarbon solvent such as toluene, xylene or trimethylbenzene. The hydrochloric acid released during the reaction is preferably neutralized with an inorganic base in an amount at least equivalent to the released acid, such as sodium hydroxide or potassium hydroxide or sodium carbonate or potassium carbonate.

[0036] The compound of formula (5) is prepared according to the method of the present invention from the compound of formula (1), and such a compound of formula (1) is reacted with a compound of formula

[0037]

Chemical formula

[0038] The reaction conditions for the preparation of the compound of formula (5) may correspond to those given above for the compound of formula (3).

[0039] The compounds of formula (3) and (5) are effective stabilizers against the harmful effects of light and heat for organic materials, especially for synthetic polymers such as polyolefins. Films, such as agricultural films made from polyolefins, are stabilized with hindered amine stabilizers to improve the long-term stability of the films.

Examples

[0040] [Example 1] Preparation of the compound of formula (102)

[0041]

Chemical formula

[0042] [Example 2] Repeat Example 1, but use a hydrogen pressure of 20×10 8 mPa (instead of 30×10 8 mPa). The compound of formula (102) is obtained in a yield of 96.7%.

[0043] [Example 3] Repeat Example 1, but use a hydrogen pressure of 180×10 8 mPa (instead of 30×10 8 mPa). The compound of formula (102) is obtained in a yield of 97.4%.

[0044] [Example 4] Repeat Example 1, but use a hydrogen pressure of 20×10 8 mPa (instead of 30×10 8 mPa) and an equimolar amount of 37 wt% aqueous formaldehyde solution (instead of 2.3 g of paraformaldehyde). The compound of formula (102) is obtained in a yield of 97.1%.

[0045] [Example 5] Repeat Example 1, but use a hydrogen pressure of 180×10 8 mPa (instead of 30×10 8 mPa), a reaction time of 12 hours (instead of 24 hours), and 10 wt% of Pd / C (instead of 4.9 wt% of Pd / C). The compound of formula (102) is obtained in a yield of 98.8%.

[0046] [Example 6] Repeat Example 1, but use a hydrogen pressure of 100×10 8 mPa (instead of 30×10 8 mPa) and 10 wt% Pt / C (instead of 4.9 wt% Pd / C). The compound of formula (102) is obtained in a yield of 96.3%.

[0047] [Example 7] Repeat Example 1, but use a reaction temperature of 130 °C (instead of 100 °C), an equimolar amount of 37 wt% aqueous formaldehyde solution (instead of 2.3 g paraformaldehyde), and 10 wt% Pt / C (instead of 4.9 wt% Pd / C). The compound of formula (102) is obtained in a yield of 96.7%.

[0048] In all of Examples 1 to 7, no dehalogenation by-products can be detected.

[0049] Comparative Example 1: Preparation using Raney Cu as the catalyst Repeat Example 1, but use 10 wt% Raney Cu (instead of 4.9 wt% Pd / C). The compound of formula (102) is obtained in a yield of 9.6%.

[0050] Comparative Example 2: Preparation using Raney Co as the catalyst Repeat Example 1, but use 10 wt% Raney Co (instead of 4.9 wt% Pd / C). The compound of formula (102) is obtained in a yield of 2.5%.

[0051] Comparative Example 3: Preparation using Raney Ni as the catalyst Repeat Example 1, but use 10 wt% Raney Ni (instead of 4.9 wt% Pd / C). The compound of formula (102) is obtained in a yield of 8.0%. Some embodiments are shown below. Item 1 Formula [Chemical formula] (wherein R 1 and R 2 are each independently C 1 ~C 8 alkyl) A method for preparing a compound of In the presence of a palladium or platinum catalyst, at a hydrogen pressure of 5×10 8 mPa to 200×10 8 mPa, reacting a compound of the formula

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Claims

1. A method for preparing a compound of formula 【Chemical 1】 (wherein, R 1 and R 2 are each independently C 1 -C 8 alkyl) , comprising the step of reacting a compound of In the presence of a palladium or platinum catalyst, at a hydrogen pressure of 5×10 8 mPa to 200×10 8 mPa, for the formula [Chemical 2] with a formaldehyde source .

2. R 1 and R 2 are each independently C 1 to C 4 alkyl, the method according to claim 1.

3. The method according to claim 1 or 2, wherein the formaldehyde source is paraformaldehyde or formaldehyde

4. The method according to any one of claims 1 to 3, which is carried out at a temperature of 50 to 180 °C

5. The method according to any one of claims 1 to 3, which is carried out at a temperature of 80 to 150 °C

6. The method according to any one of claims 1 to 5, wherein a catalyst of palladium or platinum supported on a carbon support is used

7. The method according to any one of claims 1 to 5, wherein a palladium catalyst supported on a carbon support is used

8. The method according to any one of claims 1 to 5, wherein a platinum catalyst supported on a carbon support is used

9. The method according to any one of claims 1 to 8, wherein 2 to 15% by weight of the catalyst is used based on the weight of the compound of formula (2)

10. The method according to any one of claims 1 to 9, wherein the reaction is carried out in the presence of a solvent

11. The method according to claim 10, wherein the solvent is water, hexane, methanol, toluene or xylene

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