JPS58207383A - Manufacture of 4-butanolides - Google Patents

Abstract

PURPOSE:To easily manufacture 4-butanolides with high current efficiency in high yields, by electrolytically reducing a mixture of acrylic ester with aldehyde in the state of an aqueous emulsion in the presence of a specified inorg. salt and an electrically conductive substance having the function of an interphase transfer catalyst. CONSTITUTION:A mixture of acrylic ester with aldehyde is electrolytically reduced in the state of an aqueous emulsion in an electrolytic cell provided with electrodes made of Pb or a Pb alloy and separated by a cation exchange membrane. The reduction is carried out in the presence of an inorg. salt contg. phosphate ions as a supporting electrolyte and >=1 kind of salt selected from quat. ammonium salts and quat. phosphonium salts as an electrically conductive substance having the function of an interphase transfer catalyst. The pH of the aqueous phase in the aqueous emulsion is adjusted to 6-9. By this method 4- butanolides can be obtd. under mild conditions with high current efficiency in high yields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing goubutanolides from acrylic acid esters and aldehydes, and in particular to a method for producing goubutanolides by electrolytic reductive coupling reaction. .

The goobutanolides referred to in the present invention refer to goobutanolide, that is, γ-butyrolactone and its mono-wL conversion product at the go position.

BACKGROUND ART Gobutanolides, particularly goualkyl-goobutanolides, have a unique aroma and are used as fragrances for foods and cosmetics, and are also useful as intermediates in the production of fragrances, pharmaceuticals, agricultural chemicals, and the like. For example, goo-n-propyl-goobutanolide has a coumarin-like aroma, and 44-n-~xylu-goobutanolide has a nutty aroma when concentrated, and a beach-like aroma when diluted. Each is known as a fragrance.

The following methods have been proposed for producing goubutanolides by electroreductive coupling reaction of acrylic esters and aldehydes. -1 That is, a method in which a mixture of aldehydes, acrylic esters, and trimethylsilane is homogeneously electrolytically reduced using a lead electrode using dimethylformamide as a solvent.
Dron Letters l %'im, 2/vol., pages j02 to j032 (/9/θ) J, and graphite activated in the aqueous phase by placing a mixture of ethanal and propanal in a potassium phosphate water-resistant liquid. Method of coupling with acrylic ester using an electrode (r Zn,
Org, Khim, J., Volume 1/No. 2.

Seventh? ♂g~/9♂j page (/ri 2j year) J nato.

However, when performing electrolysis in a homogeneous system, the solvent system is generally water-10tonic bath medium, water-aprotic polar solvent, or aprotic polar solvent. A possible solvent is 3PjIi. As a result of various studies on electrolytic reductive coupling reactions in a homogeneous system, the present inventors have obtained the following knowledge, which is based on the patent application number Shoj≦-/, tj7\. That is, it was confirmed that the current efficiency was extremely low in water-protic solvent. The reason for this is not well understood, but some of the aldehydes are acetalized by the solvent,
Hemiacetalization is thought to be one of the causes. In addition, in the case of water-aprotic polar solvent,
The selectivity of gobutanolide based on aldehyde is extremely low. In this case, hydroxyl ions, which are thought to be slightly generated by water electrolysis, are strengthened by the aprotic polar solvent, and i! which is undesirable for aldehydes. This may also be due to the occurrence of II reaction. Therefore, in order to conduct electrolysis in a homogeneous system while maintaining both high yield and current efficiency, it is necessary to use an aprotic polar catalyst alone, taking into account the phase heat property with water and the bath solubility of the conductive supporting salt. It seems necessary to use a special reagent such as trimethylchlorosilane. However, expensive catalysts such as dimethylformamide must be used, and trimethylchlorosilane must be used in equimolar amounts with the aldehyde, which is easily hydrolyzed by moisture to L, which is expensive. There are problems such as the need to be careful when handling the product.

On the other hand, in the latter case, the electrodes used are difficult to manufacture, and the carbon electrodes lack mechanical strength, resulting in breakage or cracking when attached to filter press type electrodes commonly used in industry. There are drawbacks such as the need to solve the pollution problem caused by the use of a water layer. Furthermore, this method 11.0 has the disadvantage that goubutanolide is obtained as a mixture of goomethyl-goobutanolide and gouethyl-goobutanolide (1-,-), which makes separation and purification complicated.

The present inventors have conducted intensive research to develop a method that can overcome the various drawbacks of the conventional methods for producing G.I. By using a specific inorganic salt as the supporting electrolyte, in the presence of a conductive substance with a phase transfer catalytic function, and by electrolytically reducing the pH of the aqueous layer in an aqueous emulsion state at a setting of 1, extremely high yields can be achieved. It was discovered17 that goubutanolides can be easily produced with high current efficiency.

The present invention was made based on the knowledge described below, and is suitable for use with expensive additives or additives that require careful handling.
In addition, the goobutanolides can be obtained with high yield and high current efficiency under mild conditions F, and the isolation operation of the product is facilitated.Furthermore, the cathode is made to have strong mechanical strength and non-toxicity, and has good electrical conductivity. The object of the present invention is to provide an industrially advantageous method for producing goubutanolides, which allows for easy separation and recovery of substances.

The method for producing gobutanolides according to the present invention is to achieve the above objectives by using a mixture of acrylic acid varnish and aldehyde, using lead or a lead alloy as an electrode, and using a cationic compound as an electrode.
A battery cell separated by a diaphragm, using an inorganic salt having phosphate ions as a supporting electrolyte, and having at least seven types of phase transfer catalyst functions selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts. In the presence of an electrically conductive substance, in an aqueous emulsion state, and in the aqueous layer of the aqueous emulsion, p
) The special feature is to carry out electrolytic reduction with I in the range of 6 to D.

The reaction of the present invention proceeds roughly according to the reaction formula shown in F.

(R in the formula is a substituted or unsubstituted alkyl group, aryl group, aralkyl group, alkenyl group, or alkynyl group, R'
is an alkyl group) In the present invention, it is necessary to carry out this reaction in an aqueous emanolytic state, that is, in a heterogeneous phase consisting of an aqueous phase and an organic phase. In this case, one drop in the aqueous phase has an important meaning in the present invention. That is, it is necessary to adjust the pH in the aqueous phase to a range of 6 to 9.

In acidic ranges below pH 116 and alkaline ranges above pH E, acrylic esters and aldehydes become unstable and 11 reactions occur, resulting in low reaction yields of goobutanolides based on acrylic esters and aldehydes. Particularly in the acidic range of pH B or higher, the production of propion ester increases and the reaction yield of acrylic ester 1'i decreases.

Also, electrode wear increases.

In the aqueous phase of the aqueous emulsion, there is 1, an inorganic salt with phosphate ions, and a '@ return' + A Y that has a phase transfer catalytic function.
(are contained in soil, and these affect pt-i.

Inorganic salts containing phosphate ions are particularly influential.

In order to adjust the pH of the aqueous layer to a range of 6 to 9, add 4 salts to an inorganic salt containing phosphate ions, that is, an alkaline phosphoric acid.
It is necessary to set it to H+~9. In order to adjust the pH of the glucali metal salt of phosphoric acid to 4 to 9, either phosphoric acid or dihydrogen phosphate is neutralized with an alkali, or alkali gold hydroxide or phosphoric acid hydrogen salt is prepared with phosphoric acid. must be neutralized.

Inorganic cations having phosphate ions used in the present invention include, for example, alkali metal cations such as sodium, potassium, lithium, cesium and rubidium, and ammonium ions, with sodium and potassium being preferred for economical reasons.

There are no particular restrictions on the use of inorganic salts containing phosphate ions, as long as the electrical resistance of the emulsion is not extremely high and the 'C'W solution can be carried out smoothly. It is used in a range of 30% by weight.

Although the aldehyde used in the present invention is not particularly limited, industrially preferred is an aliphatic aldehyde having -/3 carbon atoms, and more preferably a saturated linear aldehyde. For example, propanal, butanal, pentanal,
Hexanal, heptanal, octanal, nonatele, etc.1, inorganic compounds with phosphate ions and phase transfer catalysts such as quaternary ammonium salts or quaternary phosphonium salts are used, respectively. J
Ii T-v By applying electrolysis in the fusion state [
The yield will increase.

The degree of effectiveness of the quaternary ammonium salt and quaternary phosphonium salt used in the present invention varies depending on the type thereof. The effectiveness of quaternary menseptinium salts and quaternary phosphonium salts also differs depending on the type of aldehyde. That is, when the aldehyde has a small number of carbon atoms, for example, when the aldehyde has a carbon number of Co-Da, quaternary ammonium salts and quaternary phosphonium salts in which the total number of carbon atoms in the general formula described below is 10 or more and F2j or less are used. It is preferable to use. 1. When the number of carbon atoms in the aldehyde is large, for example, in the case of an aldehyde with a carbon number of j~/3, the current efficiency and reaction yield are lower. It is preferable to use one in which the total number of carbon atoms is 10 or more, 20 or less, and it is more preferable to use one in which the total number of carbon atoms is 76 or more. The total number of carbon atoms is 10 or more, θ
At temperatures below t, the current efficiency and reaction yield decrease.

The quaternary ammonium salts and quaternary sulfonium salts described above have the general formula (in which R1, R2, R3, and R4 are each the same).

or different alkyl or aralkyl groups), and the total number of carbon atoms in these groups is /θ~25.

X- is a unit corresponding to the monovalent anion). These quaternary I immonium salts and quaternary phosphonium salts [2] are generally Bl, H
Preference is given to those in which a, Hj and R4 are alkyl groups from the group consisting of methyl, ethyl, biyl, butyl, amyl, among others.

R1, l (at least 311 of 2, R3, and R4
It is more preferable that M is an alkyl group having 3 or more carbon atoms [
, 1, More preferably, all the alkyl groups are butyl groups. These include, for example, detra-111 or iso)-propyl, detra-(n or iso'l-
Butyl, detra(n or iso)-amyl, ena1
Examples include ammonium salts and phosphonium salts of 1-tripropyl, ethyltributyl, and ethylbrobildizonal.

The key of the quaternary ammonia l-salt and the quaternary phosphonium salt in the aqueous layer of the aqueous emulsion is θ, 0/IjlI
It is sufficient if the number is 11 to 42, and preferably θ, /hoe to ks blood filtration. If the quaternary ammonium salt and quaternary phosphonium salt have too few wrinkles, current efficiency and reaction yield will decrease.

As the counter anion X- of the quaternary ammonium salt or quaternary phosphonium salt, for example, phosphate ion, sulfate ion, halogen ion, etc. are used, but among these,
Phosphate ions are preferred [7].

Sulfate ions, halogen ions, etc. slightly reduce the reaction yield and current efficiency. Among these, halogen ions are undesirable because they increase electrode wear.

The cathode material used in the present invention [7]
Alloys containing antimony, such as hard lead containing antimony, lead-
Examples include tin alloys. These cathode materials also have a mechanical strength of 1 minute and do not cause pollution problems. Even when used in a bipolar filter press type battery case, it is capable of continuing stable operation for a long period of time.

The anode material may be any material that is sufficiently benign to the anolyte, such as lead, lead alloys, platinum, silver, or alloys mainly composed of these metals, or other metals containing these metals. Alternatively, one plated with an alloy is used.

In the method of the present invention, in order to prevent the possibility of the generation of explosive gas due to the mixing of the oxygen generated at the anode surface corresponding to the through-hole at the anode surface and the hydrogen generated slightly at the cathode surface t, when performing electrolysis, It is preferable to use a diaphragm to separate the 14-electrode chamber and the cathode chamber. As a diaphragm, a cation exchange membrane, an unglazed diaphragm, or the like may be used, but a cation exchange membrane is generally preferred.

As the anolyte, a water bath solution of an inorganic acid such as sulfuric acid or phosphoric acid is used.

The catholyte contains reactants such as acrylic varnish 1A, aldehydes and their electrolyzed products gobutanolide, adipic acid diester, propylene chloride, alcohol, and other reactants and water immersion. It is a mixture of conductive substances to increase conductivity, and exists as a two-phase system of an organic phase and an aqueous phase. In some cases, it is also possible to add an acrylic acid ester polymerization inhibitor. 7. Using emulsifiers or the like to stabilize Lujo' may have a negative effect on emulsion formation.7. - It is possible to add a catalyst as long as the
It is now possible to carry out electrolysis without using these additives or bath media.

As the acrylic ester used in the present invention, lower alkyl esters of acrylic acid are preferred from the viewpoint of bath solubility when burned in water, and furthermore, acrylic esters are inexpensive and industrially easy to handle. Methyl ester (hereinafter abbreviated as methyl acrylate) is most preferable.The cell ratio of aldehyde to acrylic ester is preferably /~10 from the viewpoint of yield; In consideration of the separation of Good to have.

The volume ratio of the organic phase in the emulsion to the total emulsion is preferably O1θS~O,S from the viewpoint of ease of product separation.

'As for the temperature during electrolysis, H-polishing is good if the aldehyde is above the boiling temperature of the acrylic ester, but usually it is 20 to 60°C, especially to prevent thermal denaturation of the aldehyde and acrylic acid ester. It is preferable that the temperature is between θ and θ°C.

Regarding the current density in the cathode direction E, -C is / A/W ~
5 o yctm" is preferable. If it is more than 7M, the productivity will be low and a wide area electrode will be required.
In this case, the heat generated by the liquid resistance is extremely large, making it impractical. Usually it is done at 5-20 AAM'.

The electrolytic reaction solution is prepared by dipping the electrolytic solution for 1 minute (preferably in a tank-type lysis tank) onto the cathode surface in a state in which the aqueous phase and the organic phase are suspended in granular form. - It is necessary to stir the electrolytic reaction solution in a sonoil terpress electrolytic cell, and it is preferable that the flow linear velocity of the electrolytic reaction solution is at least 1°C to sufficiently form an emulsion, and usually /θO This is carried out in the range of .about.da θθcw+b.

In the present invention, the treatment of the catholyte after the completion of the problem-solving reaction is carried out in a conventional manner. That is, first, the electrolytic solution is separated into two layers, an organic layer and an aqueous layer, and then the conductive substance distributed in the organic layer is extracted with a small amount of water. Next, in-house distillation is carried out to first remove low-boiling point organisms such as alcohol, and then the main reaction raw material is recovered, and then a product is obtained. On the other hand, for the aqueous layer, low boiling point materials such as alcohol
After the living organisms are removed by # addition, the water corresponding to the mobile water from the anolyte is removed by distillation, and the remaining liquid containing conductive substances is recycled and used as the aqueous layer of the catholyte. The method of the present invention is distinguished by the fact that the product can be separated very easily through such treatment, and the conductive substance can also be recovered very easily.

The advantages of the present invention are listed above.

By adjusting the pH of the aqueous phase to a range of 6 to 9 in the fly emulsion state and electrolyzing in the presence of an electrically conductive substance having a phase transfer catalytic function, coubutanolide can be produced without using expensive reagents. ? It can be obtained with extremely high current efficiency and excellent selectivity. Furthermore, the adipic acid diester produced as a by-product is also extremely important industrially. 9.2) The product is extremely easy to separate. Namely.

By simply allowing the emulsion to leave the electrolytic cell, the emulsion can be separated into a monolayer mainly composed of acrylic acid ester, aldehyde, and gobutanolide, and a water layer mainly composed of water and conductive substances. Can be easily separated. If only this m-layer is extracted and distilled, the product can be easily isolated and purified. In this #trade, many solvents like homogeneous #
There is no need for trade collection, and the utility costs are extremely low. After separating the electrolyte into two layers, the aqueous phase can be subjected to subsequent electrolysis after some treatment.

3) The conductive substance in terbutanolide can be easily separated and recovered. That is, as mentioned in 2) above, organic J-
The aqueous and aqueous layers can be easily separated and recovered in this organic layer.

As mentioned above, the present invention has great significance in that it provides a very advantageous process for producing gobutanolides from acrylic esters and aldehydes. .

Next, in order to further explain the present invention in practical terms, examples will be presented. Note that 3]l# of reaction rate, selectivity, and current efficiency was calculated using the first-order g1 formula.

Reactivity of acrylic acid ester Selectivity of goobutanolides based on acrylic ester Selectivity of goobutanolides based on aldehyde Selectivity of adipic acid diester based on acrylic ester Current efficiency However, the current efficiency is 2. 1
It was calculated assuming that moles are produced.

Example: Both the anode and cathode were lead electrodes with a current-carrying area of 01θ4tdx, and a cation exchange membrane obtained by sulfonating a divinylbenzene-styrene-butadiene copolymer with M/≦■ was used to fill the anode and cathode compartments. A partitioned H-type cell was used as an electrolytic cell.The anolyte and sulfuric acid were used.As the catholyte, 2.73 t of potassium dihydrogen phosphate was used.
Potassium hydroxide with a purity of 0.93F is bath-dissolved in water, an aqueous solution of 1-thora-n-buteran7inium phosphate is added thereto, and this water bath solution is dissolved in phosphoric acid. Adjust one mouth to 7, then butanal!, j3”
? , methyl acrylate 2.2θ? The total liquid volume is 202
A mixture was used in which water was added to give the following results. Electrolysis was carried out at a current density of /θA/lk' while maintaining the temperature of the catholyte at 2j to 3θ°C and thoroughly stirring with a magnetic stirrer. After 5 hours passed (after the start of electrolysis), the electrolysis was stopped and the catholyte was analyzed by gas chromatography [7].The reaction rate of methyl acrylate was 9145g-n-propyl-l based on methyl acrylate. -Selectivity of butanolide! Otsu, Yuo, Selection of dimethyl adipate*'s, Selectivity of 41-n-propyl-goobutanolide based on butanal was 95.4t%, and current efficiency of n-propyl-goobutanolide was ♂3.0. .

Example Sodium dihydrogen cholate 5. % Otsu? , sodium hydroxide/,3/t is bath-dissolved in water, and tetra-n-
amyl ammonium phosphate j0 bath 1&/l
Add /r, adjust this water bath solution to 7 with phosphoric acid C, then add butakar j, -ta 3v, methyl acrylate 2.20t, and add water so that the total fetit becomes 7θt. Electrolysis was carried out in the same manner as in Example 1, except that a catholyte of 1 Selectivity of dimethyl adipate/3 or less, selectivity of 41-n-propyl-goobutanolide based on butanal? t, 2To, 4t-
The current efficiency of In-propyl-goobutanolide is 76.4
It was t%.

Example 3 Using tetra-n-butylammonium sulfate instead of tetra-n-butylammonium phosphate
Electrolysis was carried out in the same manner as in Example 1, except that water bath liquids /, +, and 11 were used. The reaction rate of methyl acrylate was 91%, and 4l-n-propyl-
Selectivity of gobutanolide ♂/, 0, dimethyl adipate/%, 41-n-propyl-y- based on butyl
Selectivity of butanolide♂7. The current efficiency of ♂ Excellent and Good 〇-propyruder butanolide was 77 Excellent.

Example jθ of tetra-n-butylphosphonium postnoate instead of datetra-n-butylammonium phosphate
When electrolysis was carried out in the same manner as in Example 1, except that a water bath solution of , %, selectivity of dimethyl adipate/ti, selection of gouropropyl-goobutanolide based on butanal 4A9j, j, regret, selection of n-propyl-goobutanolide? The flow rate of 4 was 3.2%.

Example j Heptanal t5',7A instead of butanal? , vomiting time 31. Example/ except that f time is changed to 2.0 hours
When electrolysis was carried out in the same manner as above, the reaction rate of methyl acrylate j6. θ bun, 9-〇- based on methyl acrylate
Selection of hexyl-goobutanolide tF169, da, ajibire: 1 dimethyl selectivity 27.7, heptanal standard g -n --, xyl-goobutanolide selectivity 21, co-n-hexyluda-butanolide The current efficiency was 6j, Ochi.

Example 3 Preparation of tetra-n-butylammonium phosphate and tetra-n-ammonium bosphate
Electrolysis was carried out in the same manner as in Example J except that ♂♂V was used, and the reaction rate of methyl acrylate was 6.
♂, 5'*, Selection of glue-n-hexyl-goobutanolide based on methyl acrylate 4Sj9.7th, Selectivity of dimethyl adipate 2ηθ, 41- based on heptanal
Selectivity of n-hexyl-goobutanolide 7/excellent, Kuhn
-The current efficiency of Hekyleroogubutanolide is s 11.0
Example 2 5O of tetra-n-butylammonium sulfate instead of tetra-n-butylammonium phosphate
Electrolysis was carried out in the same manner as in Example J except that qb water bath solution/, g tr was used, and the reaction rate of methyl acrylate was ! t7. /To, 17- based on methyl acrylate
Selection of n-~Kyzyruder-butanolide 4At3.2, selection of dimethyl adipate 4-9/%, selectivity of 4t-n-hekizyruder-butanolide based on heptanal 74t%, 41-n-hexyl- The current efficiency of terbutanolide was λ/%.

Example! 5θ of tetra-n-butylphosphonium phosphonium phosphate instead of tetra-n-butylammonium phosphate
Electrolysis was carried out in the same manner as in Example 2, except that 7.6 V of the water bath solution was used, and the reaction rate of methyl acrylate was
t, 4t%, methyl acrylate J! 1! , Hayabusa no 41-
Selection of n-hexyl-y-butanolide*tz, 3 regrets, selectivity core of dimethyl adipate, 0%, selectivity of n-hexyl-goobutanolide based on heptanal 79.
The current efficiency of 0-hexyl-coubutanolide was 66.0%.

Comparative Example Potassium dihydrogen phosphate λ, 73v, 5θ chronological water bath removal of tetra-n-nocalan7nium phosphoate/, 6t
, water 3 da, 7/f, acrylic acid metelco, λt
, heptanal, electrolysis was carried out in the same manner as in Example J, except that a catholyte of 2V (the pH in the aqueous layer was 0.05V) was used, and the reaction rate of methyl acrylate was 0.
Unfortunately, the selectivity of Gourohexyl-goobutanolide based on methyl acrylate is 3, and the selectivity of dimethyl adipate is 6.2. , 47-n-
The current efficiency of hexyluda-butanolide is 3 yen, 3%
Met.

Patent applicant: Asahi Kasei Corporation Ne1 432-

Claims (1)

[Claims] / A battery containing a mixture of an acrylic ester and an aldehyde with a lead or lead alloy as an electrode and separated by a cation exchange membrane, using an inorganic salt having phosphate ions as a supporting electrolyte, In the presence of at least seven electrically conductive substances having a phase transfer catalytic function selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts, the pH of the aqueous layer of the aqueous emulsion is reduced to 6. A method for producing goobutanolides, characterized in that the inorganic salt having a phosphoric acid ion is an alkali gold salt of phosphoric acid. Method 3 The method according to claim 2, in which the alkali metals are natritam and potassium. The method according to claim 7, in which the aldehyde is an aliphatic aluminum hydroxide having a carbon number of λ to 13. It is an aliphatic aldehyde having 2 to 3 carbon atoms, and quaternary ammonium salts and quaternary, ↓, sulfonium salts have the general formula (quaternary ammonium salts) (quaternary phosphonium salts) (Hl-% in the formula , Hs, and R4 are the same -
or different alkyl groups or aralkyl groups, the total number of carbon atoms of these groups is 70 to coj, and X- is a unit corresponding to a monovalent anion). Method 6 according to claim 1, wherein R1, R2, R3, and R4 in the general formula are all alkyl groups, and the total number of carbon atoms of these alkyl groups is 20. Method 74 aldehyde is an aliphatic aldehyde having 5 or more carbon atoms, and the quaternary ammonium salt and quaternary phosphonium salt have the general formula (quaternary ammonium salt) (quaternary phosphonihum salt)
(In the formula, R1, R2, R1, and R4 are the same or different alkyl groups or aralkyl groups, and the total number of carbon atoms in these groups is /θ to λθ, and X- is a monovalent anion. The method according to claim 1, which is a compound represented by The method according to claim 2, wherein all the alkyl groups are butyl groups; The method according to claim ♂, wherein X- in the general formula is a unit corresponding to a monovalent phosphate ion. 178 g j , jJ and the method according to claim 7 // The method according to claim 1, wherein Nisder acrylate is a lower r-alkyl ester of acrylic acid 7.2 The lower alkyl ester of acrylic acid is a lower alkyl ester of acrylic acid 73 The method according to claim 1/claim 73, wherein the concentration of the quaternary ammonium salt and the quaternary phosphonium salt in the aqueous layer of the aqueous emulsion is θ, θ/car M The method according to claims 5 and 7 below: