JP2846939B2 - Method for producing 2,3-epoxy-2,3-dihydro-1,4-naphthoquinone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to 2,3-epoxy-2,3-dihydro-2, a raw material for synthesizing 2-hydroxy-1,4-naphthoquinone (also known as Lawson). The present invention relates to a method for producing -1,4-naphthoquinone (hereinafter abbreviated as EDNQ).

"Prior art" Production methods of EDNQ include: (1) a method in which 1,4-naphthoquinone (hereinafter abbreviated as NQ) is reacted with an aqueous alkaline hydrogen peroxide solution in a suspended state (Japanese Patent Publication No. 46-17782). (2) a method of reacting NQ with hydrogen peroxide in a water suspension in the presence of an organic base (JP-B-56-54318); (3) reacting NQ with a sodium hypochlorite aqueous solution in a water suspension Method (Chemical Abstracts. 78 , 78119x (197
3), (4) a method of reacting NQ with calcium hypochlorite in a water suspension state (Chem. Ber., 25 , 3599 (1892)), (5) NQ in an alcoholic solvent in an alkaline hydrogen peroxide solution (Chem. Ber., 61 , 1163 (1935); J.
Am. Chem. Soc., 61 , 3216 (1939)), (6) A method of reacting NQ with an aqueous solution of hypochlorite in the presence of an organic solvent incompatible with water and a phase transfer catalyst (JP-B-2) -11592) and the like.

[Problems to be Solved by the Invention] However, the EDNQ obtained in any of these cases contains a considerable amount of side reaction products and unreacted NQ, and the usually obtained EDNQ is light brown or ocher. And its purity is about 90-95% (including 1% or more of unreacted NQ).
The highest purity was 96-97%. Therefore, when these EDNQs are used as raw materials for Lawson, the obtained Lawson contains considerable impurities, and the result is not yellow but rather ocher to brown, and the purity is 94-94.
It was about 97%. Therefore, in order to obtain a high-purity Lawson, it was necessary to purify either the raw material EDNQ or the generated Lawson, or both.

An object of the present invention is to provide a high-purity EDNQ that can produce a high-purity Lawson without a purification step in the middle,
It is an object of the present invention to provide a method which can be easily, inexpensively and industrially produced at a high yield.

In particular, it aims at improving the method (6). That is, in the method (6), the oil layer of the NQ and the aqueous layer of the oxidizing agent are separately formed, and by adding a phase transfer catalyst, the reaction of both layers is smoothly performed, thereby improving the quality and yield. Things. However, during the formation of both layers, a part of the oxidizing agent is consumed by the reaction generated when the two layers are mixed, leaving unreacted NQ in the subsequent reactions, causing a decrease in the quality and purity of the obtained EDNQ. Had become.

[Means and actions for solving the problems]

The present inventors have conducted intensive studies on a method for producing a high-purity EDNQ that solves the above-mentioned problems. As a result, in the method (6), as shown in the examples, the epoxidation of NQ was carried out. When the reaction is carried out using about 1.5 mole times of hypohalite aqueous solution from the beginning, the generated EDNQ further reacts with the high-concentration and excess hypohalite present in the system. At the same time that the product was formed, it was found that this reaction consumed a large amount of hypohalite, reduced the yield of EDNQ, and resulted in unreacted NQ and low purity. Therefore, unlike the embodiment of the method (6), a phase transfer catalyst is added to the organic solvent solution of NQ to form an oil layer, and then the aqueous solution of hypohalite in the aqueous layer is gradually added according to the consumption rate. Particularly, in the latter half of the reaction when the concentration of EDNQ becomes large, an aqueous solution of hypohalite was gradually added so as to keep the concentration of hypohalite in the system (aqueous phase) low. As a result, not only can side reactions be greatly suppressed, but also the amount of hypohalite used can be reduced, and the reaction can be pushed to the point where almost no unreacted NQ remains in the product. The present inventors have found that the yield of pure EDNQ can be greatly improved, and have completed the present invention.

That is, the present invention provides a method for producing EDNQ by oxidizing NQ using an aqueous hypohalite solution in the presence of an inert organic solvent and a phase transfer catalyst which are not compatible with water, wherein the organic solvent of NQ is used. The present invention provides a method for producing EDNQ, which comprises reacting a solution while gradually adding an aqueous solution of hypohalite under stirring in the presence of a phase transfer catalyst.

In the present invention, NQ as a raw material is used after being dissolved in an organic solvent, so that any form of NQ can be used.

As the phase transfer catalyst used in the present invention, any commonly used phase transfer catalyst can be used, for example, tetrabutylammonium bromide,
Quaternary ammonium salts such as tetrabutylammonium chloride, tetraethylammonium bromide, triethylbenzylammonium chloride, and tributylbenzylammonium chloride; cyclic ethers such as crown ethers; and quaternary phosphonium salts such as tetrabutylphosphonium bromide. However, in consideration of toxicity, price, availability, ease of handling, and reactivity, a quaternary ammonium salt that is usually used is preferable in terms of catalytic effect and cost.

The amount of phase transfer catalyst used is typically 0.00
It is 1 to 0.05 part by weight, preferably 0.003 to 0.01 part by weight.

The inert organic solvent used in the present invention preferably dissolves NQ and EDNQ and is substantially incompatible with water. For example, aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane, and trichloroethylene are exemplified.

The amount of the solvent to be used may be generally an amount at which the NQ is substantially dissolved under the reaction conditions, and is usually about 1 to 30% in NQ concentration.

As the oxidizing agent for NQ used in the present invention, an aqueous solution of hypohalite is usually used. Examples of hypohalites include, for example, sodium hypochlorite, sodium hypobromite, potassium hypochlorite or potassium hypobromite. Used.

Although sodium hypochlorite also exists as a crystal, it is convenient to use an industrially commercially available aqueous solution of sodium hypochlorite because of its easy handling.

The amount of the hypohalite used is usually 1.0 to 1.5 mole times, preferably 1.1 to 1.35 mole times, more preferably 1.2 to 1.3 mole times with respect to the NQ used, and is most effective. The concentration of the aqueous solution of hypohalite is usually 5 to 15%.

The temperature of the oxidation reaction is 10 to 70 ° C, preferably 20 to 50 ° C, and the yield of EDNQ is better as the temperature is lower, but as the temperature is higher.
Since the solubility of NQ and EDNQ is high, the concentration is high, and the reaction rate is high, the productivity is high.Therefore, the reaction temperature can be appropriately selected depending on these conditions, but usually 30 to 40 ° C. It is advantageous to carry out the reaction.

It is preferable to gradually add the aqueous solution of hypohalite to the solution of NQ in an organic solvent in the presence of a phase transfer catalyst, and the longer the time, the more effective, but practically limited. The addition time depends on the stirring state, but is preferably about 40 minutes or more in consideration of the yield, purity and unreacted NQ, and practically 4 hours or less, usually about 2 hours or less. This makes it possible to produce EDNQ with high purity, high yield, and low unreacted NQ.

The present invention is generally implemented as follows. That is, raw material NQ
An aqueous solution of sodium hypochlorite is gradually added to the organic solvent solution containing the mixture at a predetermined temperature in the presence of a phase transfer catalyst while sufficiently stirring the reaction system to cause a reaction. When the reaction is performed in a single tank, the phase transfer catalyst may be added to the organic solvent solution in advance, or may be added to the aqueous sodium hypochlorite solution. In a normal reaction, the addition time is about 40 minutes or more and about 2 hours or less, but the addition rate of the aqueous solution of sodium hypochlorite can be appropriately adjusted by the stirring and heat removal capacity of the reactor. Preferably, in the latter half of the reaction, the concentration of hypochlorite in the aqueous layer may be appropriately measured to adjust the rate of addition.

After the addition is completed, after further reacting for about 0.5 to 2.0 hours,
The organic layer is separated, and EDNQ is recovered from the organic layer. When the reaction is carried out at a relatively low temperature with few impurities in the raw material, the organic solvent can be distilled off under reduced pressure and EDNQ can be recovered as a residue. In this case, the purity of EDNQ is about 96 to 98%. is there. In order to obtain EDNQ having a purity of at least 99% and containing almost no NQ, it is appropriate to concentrate the organic layer to a certain concentration, cool the concentrated solution, and filter and recover the crystallized EDNQ. is there. In this case, a recovery rate of EDNQ of 95% or more can be ensured by a method such as reconcentration of the filtrate or recirculation, and the isolation yield is 90% or more.

The stirring can be performed by any method such as mechanical stirring if sufficient stirring is performed.

〔Example〕

Examples 1 to 4 NQ 8.0 g and toluene 100 ml were added to a 500 ml bottomable separable flask and dissolved at 40 ° C. To the obtained NQ solution, 0.08 g of tetrabutylammonium bromide as a phase transfer catalyst was added, and then 40.9 g of a 12% aqueous sodium hypochlorite solution (1.3 mol times with respect to the raw material NQ) was added with stirring at 40 ° C. The time was changed to 18 minutes, 35 minutes, 55 minutes and 75 minutes, and then the reaction was carried out for 30 minutes after the addition was completed. After completion of the reaction, the aqueous layer was separated, the obtained toluene layer was washed with 40 ml of water, and the toluene layer was concentrated to dryness under reduced pressure to obtain EDNQ crystals corresponding to the respective addition times in Table 1. . In addition, purity and unreacted NQ were quantified by gas chromatography (hereinafter, referred to as GC). The results are shown in Table 1.

Comparative Example 1 8.0 g of NQ and 100 ml of toluene were added to a 500-ml bottomable separable flask and dissolved at 40 ° C. To the obtained NQ solution, 40.9 g of a 12% aqueous sodium hypochlorite solution (1.3 mol times with respect to the raw material NQ) was added, and while stirring at 40 ° C., tetrabutylammonium bromide 0.08 as a phase transfer catalyst was added.
g was added and reacted. After reaction at a reaction temperature of 40 ° C. for 60 minutes, post-treatment was carried out in the same manner as in Example 1 to obtain 8.37 g of crude crystals of EDNQ. As a result of GC analysis, EDNQ purity was 92.8%, unreacted NQ was 4.0%
And the yield was 89.1.

Comparative Example 2 8.0 g of NQ and 100 ml of toluene were added to a 500-ml bottomable separable flask and dissolved at 40 ° C. To the obtained NQ solution, 0.08 g of tetrabutylammonium bromide as a phase transfer catalyst was added, and then 40.9 g of a 12% aqueous sodium hypochlorite solution (1.3 mol times with respect to the raw material NQ) was added all at once to cause a reaction. After reacting at a reaction temperature of 40 ° C. for 60 minutes, the same post-treatment was performed as in Example 1 to obtain the same result as Comparative Example 1.

Example 5 30.05 g of NQ (purity: 96%) obtained industrially was mixed with 30 parts of toluene.
0 ml and dissolved at 50 ° C. This NQ solution was charged into a 500 ml separable flask, 0.2 g of tetrabutylammonium chloride was added to the solution, and the solution temperature was adjusted to 40 ° C. Under stirring (500 rpm), 120 ml of a 12% sodium hypochlorite solution was added to this solution at a rate of 1 ml / min for 60 minutes. After the addition was completed, the mixture was further reacted at 40 ° C. for 30 minutes, and the obtained reaction solution was raised to 50 ° C. to dissolve the precipitated crystals. After separating the aqueous layer, the organic layer was washed with 100 ml of water, and the obtained toluene solution was concentrated to dryness under reduced pressure, and 30.9 g of EDNQ crystals was dried.
I got As a result of analyzing the crystals by CG, the purity of the EDNQ crystals was 96.3%, the unreacted NQ was 0.8%, and the yield was 93.7%.
Met.

Comparative Example 3 The same amount of the NQ solution prepared in the same manner as in Example 5 was charged into a 500-ml bottomable separable flask, and 120 ml of a 12% aqueous solution of sodium hypochlorite was added to adjust the liquid temperature to 40 ° C.
0.2 g of tetrabutylammonium chloride was added to this liquid with stirring to start the reaction. After reacting for 60 minutes, the same treatment as in Example 5 was performed to obtain 30.7 g of EDNQ crystals containing 91.0% purity and 4.5% unreacted NQ. The yield of this EDNQ is 87.9%
Met.

[Effects of the Invention] According to the present invention, the reaction can be easily controlled and EDNQ can be easily added by gradually adding an aqueous solution of hypohalite.
It is possible to suppress side reactions such as analysis reaction of EDNQ, and the yield and purity of EDNQ to be produced are greatly improved.
And EDNQ with a purity of 99% or more can be obtained in good yield only by crystallizing the crystals.

Claims (2)

(57) [Claims] (1) 1,4-naphthoquinone is oxidized with an aqueous hypohalite solution in the presence of an inert organic solvent incompatible with water and a phase transfer catalyst to give 2,3-epoxy-2, 3−
In the method for producing dihydro-1,4-naphthoquinone, a phase transfer catalyst is added to an organic solvent solution of 1,4-naphthoquinone to form an oil layer, and the hypohalous salt aqueous solution is stirred under a stirring rate according to the consumption rate. 2,3-epoxy-2,3-dihydro-1,4 characterized by reacting while gradually adding
-A method for producing naphthoquinone. 2. The method according to claim 1, wherein the aqueous solution of hypohalite is an aqueous solution of sodium hypochlorite.