JPH0670133B2 - Lipoamide membrane and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lipoamide membrane and a method for producing the same, and more specifically, it has an excellent electron transfer function and is useful for selective reduction reactions of various organic compounds. The present invention relates to a useful lipoamide membrane and a method for producing the same.

[Prior Art] In recent years, extensive studies have been conducted to apply an electron transfer system mediated by a substance having an electron transfer ability to various organic syntheses. Lipoamide is known as one of such electron-transporting substances. However, when this product is directly used as a catalyst, there is a disadvantage that separation / collection after the reaction is difficult.

Therefore, the present inventors previously disclosed an electron-transporting polymer film in which the above-mentioned lipoamide is bonded to polyglutamate excellent in film-forming property by an amide-type bond [Journal
Of Polymer Science, Polymer Chemistry Edition, Volume 23, Page 223, 1985 (J. Polymer
Science, Polymer Chem. Ed., 23 , 223 (1985)].

[Problems to be Solved by the Invention] However, the membrane to which this lipoamide is bound is
There is a problem that the electron transfer rate through the film, that is, the electron transfer rate is not sufficient, and it is not suitable for practical use, for example, as a catalyst for a redox reaction.

The present invention solves the conventional problems described above, and in a lipoamide membrane having a basic structure in which lipoamide is bound to a matrix made of polyglutamate, the electron transfer rate through the membrane is very high, and various redox reactions are performed. An object of the present invention is to provide a lipoamide membrane useful as a catalyst for the above and a method for producing the same.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors have conducted extensive studies focusing on the structure of lipoamide to be bound to polyglutamate, and the binding method thereof. First, as a lipoamide that binds to polyglutamate, a lipoamide derivative having a specific structure, that is, a pyridine nucleus is adopted, and the nitrogen atom on the pyridine nucleus of the lipoamide derivative is further bound to polyglutamate by a quaternization reaction. The present invention was completed by confirming the results.

That is, the lipoamide film of the present invention is characterized by being composed of polyglutamate having a lipoamide derivative having a pyridine nucleus as a branch, and the production method thereof is such that the nitrogen atom on the pyridine nucleus of lipoamide is converted by a quaternization reaction. It is characterized by including a step of binding to polyglutamate.

Furthermore, the lipoamide membrane of the present invention may have a structure in which the polyglutamate is further crosslinked with 1,4-diazabicyclo [2.2.2] octane.

[Detailed Description] The lipoamide membrane of the present invention comprises a polymer matrix of polyglutamate to which a lipoamide derivative having a pyridine nucleus is bound.

First, as the polyglutamate serving as the polymer matrix, for example, poly (γ-methyl-D-glutamate),
Poly (γ-ethyl-D-glutamate), Poly (γ-normalpropyl-D-glutamate), Poly (γ-isopropyl-D-glutamate), Poly (γ-isobutyl-D-glutamate), Poly (γ-cyclohexyl) -D-glutamate) and poly (γ-isopentyl-D-glutamate), among which poly (γ-methyl-D-glutamate) (PMG) having a repeating unit represented by the following formula [I]
Is preferred.

The molecular weight of such polyglutamate is preferably 10,000 to 200,000.

The lipoamide derivative introduced into this polyglutamate is not particularly limited as long as it is a lipoamide derivative having a pyridine nucleus, and in particular, N-picolyl lipoamide represented by the following formula [II] is used. It can be mentioned as a suitable one.

In this N-picolyl lipoamide, the nitrogen atom of the pyridine nucleus has a quaternary salt structure and is bound to the polyglutamate.

The lipoamide film of the present invention may have a structure in which polyglutamate is further crosslinked with 1,4-diazabicyclo [2.2.2] octane (DABCO).

Next, a method for producing the lipoamide film of the present invention will be described.

This manufacturing process can be performed, for example, by the three-step reaction described below.

First, a lipoamide derivative is synthesized by the first-step reaction. That is, taking the above-mentioned N-picololylpoamide as an example, lipoic acid and 4-aminomethylpyridine are reacted in the presence of dicyclohexylcarbodiimide. The reaction temperature at this time is preferably -10 to 30 ° C, and the reaction time is preferably 0.5 to 100 hours.

Then, as a second step reaction, a polyglutamate copolymer is synthesized. This step will be described by taking the above-mentioned PMG as an example. First, PMG is reacted with, for example, bromopropanol in an acidic solvent, and this transesterification reaction causes a methyl group at the γ-position of the repeating unit represented by the formula [I]. With a bromopropyl group. Examples of the solvent used in this reaction include dichloroethane, methylene dichloride, tetrachloroethane, chlorobenzene and the like. In this transesterification reaction, PMG 5-9
5 mol% poly (γ-bromopropyl-glutamate)
Converted to (PBPG).

Then, by the reaction of the third step, which is a feature of the present invention,
A matrix composed of PMG is obtained, and the N-picolyl lipoamide is introduced into the matrix by binding the nitrogen atom on the pyridine nucleus of the N-picolyl lipoamide by a quaternization reaction. Obtain a lipoamide membrane. That is, the copolymer of PMG and PBPG obtained above is reacted with N-picolyl lipoamide in a solvent. At this time, the amount of N-picolyl lipoamide used is preferably set to 1 to 100 mol% with respect to the number of moles of PBPG. Examples of the solvent used include dimethylformamide, dimethylsulfoxide, sulfolane, N-
Examples include methylpyrrolidone. Thereafter, the solution is cast on a glass plate to form a film, whereby the lipoamide film of the present invention is obtained. At this time, the casting temperature is preferably 25 to 150 ° C., and the casting time is preferably 0.5 to 100 hours.

Incidentally, when the PMG matrix has a structure further crosslinked with DABCO, DABCO may be added to one end in the solvent, and the amount of DABCO used is relative to the number of moles of PBPG.
It is preferably 0.1 to 100 mol%.

[Examples] A. Production of lipoamide membrane (1) Synthesis of lipoamide derivative (N-picolyl lipoamide) 2.06 g (10 mmol) of lipoic acid was dissolved in 30 ml of acetonitrile, and dicyclohexylcarbodiimide was dissolved in the solution under ice cooling. 2.2 g (11 mmol) was added. Then, 1.0 ml (10 mmol) of 4-aminomethylpyridine was gradually added dropwise to 0-
Stirring was continued at 5 ° C for 3 days. After completion of the reaction, the precipitated dicyclohexylurea was filtered off and the solvent was distilled off. This residue was purified with a silica gel column (solvent: tetrahydrofuran), dissolved in chloroform, a 1N hydrochloric acid-saturated saline 1: 1 mixed solution was added, and the product was extracted as a hydrochloride into an aqueous phase. The aqueous phase was ice-cooled, saturated sodium carbonate was added for neutralization, and the base product was extracted with chloroform to obtain 0.57 g (yield 19%) of N-picolyl lipoamide. I
The product was identified by R, NMR and elemental analysis and confirmed to be the desired product.

(2) Synthesis of γ-bromopropyl-γ-methylglutamate copolymer (PBPG) PMG 4.8 g (0.034 mol) having a number average molecular weight of 61,000 was dissolved in 50 ml of dichloroethane, and bromopropanol 4.73 g was added thereto.
(0.034 mol) and p-toluenesulfonic acid 12.6 g (0.06 mol)
6) was added and transesterification was carried out at 60 ° C. for 24 hours. The methanol generated during the reaction was removed outside the system. After completion of the reaction, the reaction solution was poured into methanol to precipitate the polymer, and the polymer was recovered to obtain a copolymer containing 53 mol% of γ-bromopropylglutamate, that is,
I got PBPG.

(3) Production of Lipoamide Membrane 1 g of PBPG (0.0044 mol in terms of Br group) obtained above was dissolved in 10 ml of dimethylformamide. In addition to this, 0.68 g (0.0022 mol) of N-picolyl lipoamide and DAB
After dissolving 0.12 g of CO (0.0011 mol), this solution was cast on a glass plate, kept at 60 ° C. for 20 minutes in a sealed state, and then dried in an open system for 60 minutes to form a film. This resulted in 0.76 mmol of lipoamide units.
A 20 μm thick film containing / g was obtained. The film was thoroughly washed with water and methanol to completely remove unreacted lipoamide and amines.

B. Diaphragm redox reaction using lipoamide membrane A glass cell was prepared using the lipoamide membrane obtained above.
Partition into two compartments, and one compartment as a reducing agent, 7
An aqueous solution of sodium hyposulfite (Na ₂ S ₂ O ₄ ) having a concentration of × 10 ^-2 was added, and methylene blue (MB) having a concentration of 1.7 × 10 ^-5 was added to the other compartment. as shown in III], it was carried out the reduction reaction of the methylene blue by S ^₂ ▲ O ^2- ₄ ▼ ions to leuco methylene blue (leuco MB).

The progress of this reduction reaction was followed by measuring the visible absorption spectrum of the aqueous solution. In other words, the absorption maximum wavelength of MB
Measure the time change of absorbance at 666 nm, and measure MB → leuco
The reduction rate k of MB was determined by the first-order plot method. as a result, Met.

Further, when MB was similarly reduced using tributylphosphine (Bu ₃ P) instead of the above Na ₂ S ₂ O ₄ as a reducing agent, k = 3.2 × 10 ^-4 min ^-1 there were.

When no reducing agent was added, MB was not reduced even after 24 hours.

In addition, leakage of MB through the lipoamide membrane and
It was confirmed that there was no leakage of Na ₂ S ₂ O ₄ or Bu ₃ P.

[Effects of the Invention] As is clear from the above description, the lipoamide film of the present invention has an excellent electron transfer function. Therefore, when it is used for, for example, a diaphragm redox reaction, an inexpensive reducing agent is used to form an organic compound under mild reaction conditions. Its industrial value is extremely large because it can perform selective reduction of compounds, and besides, it is expected to have wide application in various fields of chemical synthesis as a polymer film having an electron transfer function. .

Claims (3)

[Claims] 1. A lipoamide membrane comprising polyglutamate having a branch of a lipoamide derivative having a pyridine nucleus. 2. The lipoamide membrane according to claim 1, wherein the polyglutamate is further crosslinked with 1,4-diazabicyclo [2.2.2] octane. 3. A method for producing a lipoamide film, which comprises a step of binding a nitrogen atom on the pyridine nucleus of a lipoamide derivative having a pyridine nucleus to polyglutamate by a quaternization reaction.