JP2000143630A - Recovery of 4-dimethylaminopyridine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover the subject compound from a by-product of a rearrangement reaction of a cyclohexanedione-based compound at a relatively low temperature in an excellent recovery ratio, useful as a rearrangement catalyst for the rearrangement reaction by decomposing a specific compound in a slightly water-soluble organic solvent in the presence of water. SOLUTION: A compound of formula I [R1 and R2 are each H or a lower alkyl; X1 to X6 are each H, a (substituted) alkyl or a heterocyclic ring containing S or the like in the ring] is decomposed in a slightly water-soluble organic solvent such preferably toluene in the presence of water to recover the objective compound. In the case of using a real reaction solution in which 4-dimethylaminopyridine is used in the rearrangement reaction from an O-acyl compound into a C-acyl compound, 4-dimethylaminopyridine and the compound of formula I are extracted by using an aqueous solution of a mineral acid such as hydrochloric acid, etc., from the reaction solution, excessive water is distilled away and the compound of formula I is decomposed preferably at 100-110 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for recovering 4-dimethylaminopyridine (hereinafter referred to as DMAP).

[0002]

2. Description of the Related Art DMAP is used as a catalyst for various reactions, particularly as a catalyst for rearranging an O-acyl compound of a cyclohexanedione compound into a C-acyl compound. Then, as a side reaction, a reaction product of DMAP and the cyclohexanedione compound is generated. Conventionally, the reaction was pyrolyzed at 130-140 ° C. for 6-7 hours to give DM
Although AP was recovered, there were problems that the recovery rate was poor, cyclohexanedione-based compounds could not be recovered, and the decomposition temperature was high, so that it could not be said to be an industrial recovery method.

[0003]

SUMMARY OF THE INVENTION The present inventors have developed DMAP.
As a result of intensive studies on an industrially advantageous recovery method, the present inventors have found that the above problem can be solved by hydrolyzing the reaction product, and solved the present invention. That is, the present invention relates to the formula [1]

Embedded image (Wherein, R ₁ and R ₂ each represent a hydrogen atom or a lower alkyl group, and X _{1 to} X ₆ each represent a hydrogen atom, an alkyl group which may have a substituent, or a sulfur atom or an oxygen atom in the ring thereof. The compound represented by the formula (1) is decomposed in a poorly water-soluble organic solvent in the presence of water.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The compound applicable to the present invention is not particularly limited, and _one of R ₁ and R ₂ is a hydrogen atom and the other is a lower alkyl group such as methyl, ethyl, propyl, etc. X ₁ , X ₂ , X ₄ , X ₅ and X _{6 each} have a hydrogen atom and X ₃ has a heterocyclic group such as lower alkylthio lower alkyl such as ethylthiopropyl, 3-tetrahydrothiopyranyl and 4-tetrahydropyranyl. Compounds can be exemplified.

[0005] As a poorly water-soluble organic solvent that can be used for the decomposition, toluene, xylene, chlorobenzene and the like can be used, but toluene is preferable in view of the decomposition temperature and the like. When the decomposition is carried out using an actual reaction solution used for a rearrangement reaction of an O-acyl compound to a C-acyl compound using DMAP, this reaction solution is treated with an aqueous solution of a mineral acid such as hydrochloric acid to obtain D
After extracting the MAP and the compound represented by the formula [1], adding a poorly water-soluble organic solvent as needed, further neutralizing with a base such as caustic soda, and decomposing excess water, 90 to 130 ° C., preferably It is performed in the range of 100 to 110 ° C. After the decomposition is completed, a treatment such as washing with water is performed to obtain DMAP.
Can be recovered as an organic solvent. Of course, DMAP can be isolated if necessary, but it is usually used as a solution repeatedly for the next rearrangement reaction.

Further, at the time of the decomposition, the decomposition proceeds more smoothly by the presence of an amine such as dimethylamine or certain mercaptans such as t-butyl mercaptan and ethyl mercaptan. The compound represented by the formula [1] has a tautomer depending on the types of the substituents of X _{1 to} X ₆ , but the present invention includes all such compounds.

The present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. [Example 1] DMAP extracted from a rearrangement reaction solution using dilute hydrochloric acid using 25.66 g of DMAP (1
8.43 g; 71.8%) and formula [2]

Embedded image DMAP represented by the formula and 5- (2-ethylthiopropyl)
To an aqueous solution (containing dimethylamine, 0.42 g) containing a reaction product with 2-butanoylcyclohexen-2-one-1 (abbreviated as APA: 7.44 g; 9.1%), 435 g of toluene and 28 g of 28 135% aqueous sodium hydroxide solution
Was added, and the mixture was sufficiently stirred and allowed to stand. The solution separated into a toluene layer, an aqueous layer and an intermediate layer containing APA. After removing the aqueous layer, the toluene layer and the intermediate layer were heated, and water was distilled off by azeotropic distillation until the internal temperature reached 100 ° C. 100-105 ° C
After heating for 2 hours to decompose APA, the mixture was cooled, a small amount of water (6 g) was added, liquid separation was performed, and the aqueous layer was combined with the first aqueous layer and extracted with 435 g of toluene. HPL combining the toluene layers
As a result of analysis by C, DMAP containing 20.05 g contained 108.8% of the recovery in the aqueous layer and 78.1% of the amount used in the reaction.

[Embodiment 2] Equation [3]

Embedded image 3.87 g (10 mmol) of the compound represented by the formula was placed in 75 g of toluene, and 4 g of water and 0.18 g (2 mmol) of a 50% aqueous dimethylamine solution were added. Internal temperature is 105 ° C
After azeotropic dehydration to remove water, the mixture was heated at that temperature for 2 hours. As a result of analysis by HPLC, DMAP 1.2
0 g (9.82 mmol: yield 98.2%) was produced,
The residual amount of the compound represented by the formula [3] was 0.01 g or less.

Example 3 DM extracted from a rearrangement reaction solution using 7.45 g of DMAP with dilute hydrochloric acid
AP (5.79 g; 77.7%) and formula [4]

Embedded image (O-APA: 2.85 g; 1)
(Equivalent to 3.1%) was added to 150 g of toluene and 70 g of a 28% aqueous solution of caustic soda. The solution was separated into a toluene layer, an aqueous layer and an intermediate layer containing O-APA. After removing the aqueous layer, 2.19 g of dimethylamine hydrochloride was added to the toluene layer and the intermediate layer, and the internal temperature was adjusted to 9%.
Water was distilled off by azeotropic distillation until the temperature reached 5 ° C. 95-
After heating at 100 ° C. for 4 hours to decompose O-APA,
After cooling, a small amount of water (4 g) was added, and the mixture was separated. The aqueous layer was combined with the first aqueous layer and extracted with 150 g of toluene. The toluene layer was combined and analyzed by HPLC. As a result, it contained 6.36 g of DMAP, and the recovery was 109.8% based on the amount in the aqueous layer, and 85.4% based on the amount used in the reaction.

Reference Example 1 D extracted from a rearrangement reaction solution using 25.66 g of DMAP with dilute hydrochloric acid
To an aqueous solution (same as in Example 1) containing MAP (18.43 g; 71.8%) and APA represented by the formula [2] (7.44 g; equivalent to 9.1%), 435 g of toluene and 28% 135 g of an aqueous solution of caustic soda was added, and the mixture was sufficiently stirred and allowed to stand. The solution separated into a toluene layer, an aqueous layer and an intermediate layer containing APA. After separating the toluene layer, the aqueous layer and the intermediate layer were further extracted with 435 g of toluene. The toluene layer was combined and analyzed by HPLC. As a result, it was found that DMAP contained 17.91 g and the recovery was 97.2% based on the amount in the aqueous layer and 69.8% based on the amount used in the reaction.

Comparative Example 1 24.0 g of an intermediate layer containing 5.64 g of O-APA obtained from a rearrangement reaction solution using 16.6 g of DMAP was added with 10 m each of water and toluene.
After adding 1 l, the pH was adjusted to 8 to 9 with hydrochloric acid. After heating this solution to distill off the solvent and water, it was further heated at 140 ° C. for 7 hours. As a result of analyzing the reaction solution by HPLC, 1.27 g was obtained.
DMAP (66% of theory from O-APA)
However, DMAP could not be separated from these by simple means because of many by-products and could not be used for the reaction of the next lot.

[0012]

According to the recovery method of the present invention, D is obtained by hydrolysis.
Since MAP is recovered, the reaction proceeds at a relatively low temperature of 90 to 110 ° C., which is useful as an industrial recovery method. Furthermore, since it can be recovered as an organic solvent solution used in the rearrangement reaction, it can be used as it is in the next rearrangement reaction, and is obtained by decomposing DMAP from the reactant [5]

Embedded image This is an excellent recovery method such that the cyclohexane compound represented by the formula (1) can be recovered.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Matsushita 300, Mukainohonmachi, Takaoka, Toyama Japan Nippon Soda Co., Ltd. (72) Inventor Shuji Noguchi 300, Mukainohonmachi, Takaoka, Toyama, Japan Nippon Soda Co., Ltd. Terms (reference) 4C055 AA01 BA01 CA01 DA52 DB01 DB02 FA41

Claims (4)

[Claims] 1. A compound of the formula [1] (Wherein, R ₁ and R ₂ are each independently a hydrogen atom or a lower alkyl group; X _{1 to} X ₆ are each a hydrogen atom, an alkyl group which may have a substituent, or a sulfur atom in the ring thereof) Or a heterocyclic group containing an oxygen atom).) A method for recovering 4-dimethylaminopyridine, comprising decomposing a compound represented by the formula: in a poorly water-soluble organic solvent in the presence of water. 2. X ₃ is a lower alkylthio lower alkyl group,
The method according to claim 1, wherein the compound is a 3-tetrahydrothiopyranyl group or a 4-tetrahydropyranyl group. 3. The method according to claim 1, wherein the organic solvent is toluene.
The collection method described. 4. The method according to claim 1, wherein the decomposition is carried out in the presence of a secondary amine.
4. The recovery method according to any one of claims 1 to 3.