JP2007084506A - Method for producing croconic acid compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a croconic acid compound, capable of being safely and economically performed in an industrial scale. <P>SOLUTION: This method for producing the croconic acid compound comprises oxidizing tetrahydroxybenzoquinone in the presence of an inorganic base containing an alkali metal, crystallizing the obtained reaction product, and then subjecting the crystallized alkali metal croconate crystals to a solid-liquid separation to isolate the crystals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a croconic acid compound. Furthermore, the present invention relates to a method for producing croconic acid which is useful as a synthetic intermediate for near-infrared dyes.

  The near-infrared dye is a dye having an absorption maximum in the near-infrared region of 750 to 1100 nm, and is a positive photosensitive lithographic printing plate (Patent Documents 1 and 2), a photothermographic material (Patent Document 3), and a silver halide. Photographic materials (Patent Document 4), optical films (Patent Documents 5 and 6), and image forming materials (Patent Document 7) for forming marks such as barcode patterns have been studied and reported. Yes. As typical near-infrared dyes, squarylium dyes, croconium dyes, and oxadibenzofurocyanine dyes are known.

  The croconium dye is synthesized by a condensation reaction of croconic acid, which is a 5-membered ring compound, with N, N-dialkylaniline, a heterocyclic active methylene compound, 2- (N, N-dialkylamino) thiophene, or the like (for example, non-patented). Reference 1). Croconic acid is a key intermediate in the synthesis of croconium dyes, and various synthetic methods are being studied.

In 1930, the formation of croconic acid as a mixture with rosic acid and triquinoyl was confirmed by oxidation of inositol with fuming nitric acid in 1930 (Non-patent Document 2).
Non-Patent Document 3 discloses a method for obtaining a croconic acid compound by reacting inositol hexanitrate with a secondary amine, but nothing is described regarding yield and the like.
Non-Patent Documents 4 and 5 disclose that tetrahydroxybenzoquinone is oxidized with manganese dioxide in the presence of potassium carbonate to convert to croconic acid skeleton, and croconic acid is isolated as a barium salt, and then protonated with sulfuric acid to produce croconic acid. Is disclosed.

On the other hand, in recent years, the environmental load of chemical manufacturing processes has been seen as a problem, and there is a need for clean chemical reactions that have little waste and do not use harmful solvents or reagents as much as possible. (For example, Non-Patent Document 6).
Japanese Patent Laid-Open No. 10-26851 JP 2002-365792 A JP 2000-160042 A JP 2001-83663 A JP 2001-194522 A JP 2004-52028 A JP 2001-294785 A Liebigs Ann Chem. , 935 (1993) J. et al. Am. Chem. Soc. 52, 2483 (1930) Tetrahedron Lett. 31, 1797 (1990) Chem Ber. 93, 1451 (1960) Chemical World, Phase 3, 139 (1999) Chemistry Frontier 4 “Green Chemistry”, Chemistry Doujinshi, GSC Network, November 30, 2001

In the methods described in Non-Patent Document 2 and Non-Patent Document 3, the reaction control of nitric acid oxidation is difficult, harmful nitrogen oxides are easily generated, and the nitrate ester produced as an intermediate is explosive. Due to the danger, it is not suitable for mass synthesis and has little practicality. In addition, in the methods described in Non-Patent Document 4 and Non-Patent Document 5, insoluble barium sulfate is formed when protonating barium croconate with sulfuric acid, and the fluidity of the reaction liquid when removing this is determined. The present inventors have clarified that the filterability is extremely poor and is not suitable for mass production.
Thus, the conventional method for producing croconic acid compound has never been an advantageous method in consideration of safety, consideration for the environment, suitability for scale-up, cost, and the like.
Therefore, the problem to be solved by the present invention is to solve the above-mentioned problems and to provide a method for producing a croconic acid compound that can be carried out safely and economically on an industrial scale.

In view of the above circumstances, the present inventors have intensively studied on a method for producing a croconic acid compound. As a result, the inventors have confirmed that the above-described problems can be solved by the following novel means, and have completed the present invention. It is.
[1] A process for producing a croconic acid compound comprising the following steps:
(Step 1) A step of oxidizing tetrahydroxybenzoquinone in the presence of an inorganic base containing an alkali metal,
(Step 2) Step of precipitating an alkali metal croconate as a crystal by crystallization from the obtained reaction product, and
(Step 3) Step [2] of isolating a crystal of an alkali metal croconate by solid-liquid separation. The inorganic base containing the alkali metal is an alkali metal hydroxide, an alkali metal alkoxide, an alkali metal carbonate or an alkali metal. The production method according to [1], which is selected from the group consisting of bicarbonates.
[3] The inorganic base containing the alkali metal is sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate and carbonic acid. The method according to [1], wherein the method is selected from the group consisting of potassium hydrogen.
[4] The production method according to any one of [1] to [3], wherein a transition metal oxide is used as an oxidizing agent in the (Step 1).
[5] The production method according to any one of [1] to [3], wherein manganese dioxide (IV) is used as an oxidizing agent in the (Step 1).

  According to the production method of the present invention, it is possible to produce a croconic acid compound without using highly dangerous nitric acid, or generating nitric ester intermediates and barium sulfate which is difficult to handle due to poor filterability. it can. For this reason, according to the present invention, a croconic acid compound can be produced safely and economically on an industrial scale.

  Below, the manufacturing method of the croconic acid compound of this invention is demonstrated in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The croconic acid compound referred to in the present invention is a general term for croconic acid, croconic acid salts, and croconic acid derivatives. If the production method of the present invention is used, such a croconic acid compound can be produced via the alkali metal croconate obtained by (Step 1) to (Step 3) of the present invention.

(Step 1) of the production method of the present invention is a step of oxidizing tetrahydroxybenzoquinone in the presence of an inorganic base containing an alkali metal.
The tetrahydroxybenzoquinone used as the raw material used in (Step 1) may be 2,3,4,6-tetrahydroxy-1,4-benzoquinone or 3,4,5,6-tetrahydroxy-1 , 2-Benzoquinone. Preference is given to 2,3,5,6-tetrahydroxy-1,4-benzoquinone. These tetrahydroxybenzoquinones can be obtained by purchasing from Tokyo Chemical Industry Co., Ltd.

  Preferred examples of the inorganic base containing an alkali metal used in (Step 1) include alkali metal hydroxides, alkali metal alkoxides, alkali metal carbonates, and alkali metal bicarbonates. More specifically, sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate are preferred. Sodium, potassium hydroxide, sodium carbonate, and potassium carbonate can be preferably used. The most preferred base in (Step 1) of the present invention is sodium carbonate or potassium carbonate.

  The molar ratio of the base used in (Step 1) is usually in the range of 3.0 to 20 times the molar amount of the raw material tetrahydroxybenzoquinone, but the reaction rate is exceeded even if it is used in excess of this range. And the yield of the target product is not significantly affected. On the other hand, if the base is used in an excessive amount, it causes problems in the process operation such as deterioration of the fluidity of the reaction mixture, and increases the amount of waste and increases the cost. The preferable usage-amount of the base with respect to the tetrahydroxy benzoquinone in (process 1) of this invention is 3.5-10 times mole, More preferably, it is 3.5-6.0 times mole.

  In (Step 1) of the present invention, it is preferable to use an oxidizing agent that oxidizes tetrahydroxybenzoquinone. The oxidant used in (Step 1) is preferably a transition metal oxide. Specific examples of the transition metal oxide include silver (I) oxide, copper (II) oxide, mercury (II) oxide, chromium trioxide (VI), manganese dioxide (IV) and the like. A preferred oxidizing agent is manganese (IV) dioxide. The molar ratio of the oxidizing agent used in the reaction is usually in the range of 2.0 to 15 times the molar amount of the raw material tetrahydroxybenzoquinone. Excessive use beyond this range does not significantly affect the reaction rate and yield, but rather increases the amount of waste and increases costs, which is an obstacle in industrial scale production. In the production method of the present invention, the preferred amount of oxidizing agent used for tetrahydroxybenzoquinone is 2.5 to 10 times mol, more preferably 3.0 to 7.0 times mol.

  The reaction solvent that can be used in the production method of the present invention does not cause problems in process operations such as impossibility of stirring, does not hinder the progress of the reaction, and adversely reacts and decomposes under the production conditions of the present invention. Is not particularly limited, for example, alcohol solvents such as 2-methyl-2-propanol, sulfone solvents such as dimethyl sulfone, diethyl sulfone, sulfolane, 2,4-dimethyl sulfolane, methyl-tert-butyl ether, anisole And ether solvents such as ethyl acetate, n-butyl acetate, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, acetonitrile, propionitrile, water, dimethyl sulfoxide and the like. Among these, sulfone solvents such as dimethyl sulfone, diethyl sulfone, sulfolane, 2,4-dimethyl sulfolane, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, propionitrile, and water are preferable as the solvent, sulfolane, acetonitrile, Propionitrile and water are more preferred. The most preferred reaction solvent in the present invention is water.

  In (Step 1) of the present invention, the reaction temperature at which tetrahydroxybenzoquinone is oxidized in the presence of an inorganic base containing an alkali metal is usually in the range of 30 ° C to 140 ° C. Since it accompanies carbonic acid, it is preferable to heat to improve the reaction rate. The preferred reaction temperature is 65 ° C to 140 ° C, more preferably 80 ° C to 110 ° C. The reaction time varies depending on the amount of tetrahydroxybenzoquinone used as a raw material, the reaction temperature, etc., but is usually 30 minutes to 5 hours.

  The reaction mixture after completion of the oxidation reaction is preferably post-treated by filtering to remove insoluble matters. In the filtration, a filter aid such as celite or florisil may be used, and an excessively used oxidizing agent or the like is removed by this operation.

Next, (Step 2) of the present invention is performed. (Step 2) is a step of precipitating croconic acid alkali metal salt as crystals by crystallization from the obtained reaction product.
When the reaction mixture obtained in (Step 1) is cooled and crystallized, the alkali metal croconate precipitates as crystals. It is also possible to crystallize and precipitate the alkali metal croconate by adding a poor solvent to the reaction mixture. Considering the yield and purification effect, a method of depositing an alkali metal croconate by adding a poor solvent while cooling is advantageous. Compared with the methods described in Non-Patent Documents 4 and 5 in which barium chloride is added to precipitate barium croconate, it is not necessary to use a new reactant and the operation is simple. This is one of the great advantages of the production method of the present invention.
Examples of the poor solvent for precipitating the alkali metal croconate include lower alcohols having 1 to 4 carbon atoms, acetonitrile, propionitrile and the like, and preferably used solvents are methanol, 2-propanol and acetonitrile.

Next, (Step 3) of the present invention is performed. (Step 3) is a step of isolating the crystals of alkali metal croconate by solid-liquid separation.
The method for solid-liquid separation is not particularly limited, and a commonly used method can be appropriately selected and used. Examples thereof include methods such as filtration, centrifugal filtration, gravity precipitation method filtration, and suction filtration. Preference is given to filtration. The precipitated alkali metal croconic acid salt can be easily isolated.

  The alkali metal croconate obtained by the production method of the present invention may be used as a croconate as it is, or may be converted into croconate, other croconate, or croconate derivatives.

Among these, since croconic acid is useful as a synthetic intermediate for a croconium dye, it is preferable that the alkali metal croconate obtained in (Step 1) to (Step 3) is protonated and converted to croconic acid. Conversion to croconic acid can be carried out by various known methods in the art. For example, it can be carried out by allowing an acid to act on a solution or suspension of an alkali metal croconic acid salt. The amount of the acid used is 2 equivalents or more, preferably 2.1 equivalents to 3.5 equivalents with respect to the alkali metal croconate. As the kind of acid, a mineral acid is preferable, and specific examples include hydrohalic acid, sulfuric acid, nitric acid, phosphoric acid and the like, but a more preferable acid is hydrochloric acid. Examples of the solvent used to bring the alkali metal croconate into a solution or suspension include water, lower alcohols having 1 to 4 carbon atoms, acetonitrile, propionitrile, and the like. It is preferable to use a solvent system that dissolves croconic acid formed by freezing, but does not dissolve alkali metal mineral salts. More preferred is methanol, ethanol, 2-propanol, acetonitrile, or a combination system of two to three solvents selected from these. The amount of the solvent to be used is 2 to 50 times, preferably 4 to 30 times, and more preferably 5 to 20 times by mass ratio to the alkali metal croconate. Alkali metal mineral salts that precipitate after protonation (for example, potassium chloride formed when protonated with croconic acid with hydrochloric acid can be easily removed by filtration). The following are concentrated, crystallized and extracted. Croconic acid can be isolated by applying a conventional separation / purification means in chemical engineering such as the above.
It is also possible to make the alkali metal croconate free using a polystyrene / sulfonic acid type strongly acidic ion exchange resin or the like, which is one of the preferred embodiments of the present invention. Since the used ion exchange resin can be recovered and reused, it is industrially advantageous.

  If croconic acid is used, various useful compounds can be further produced. For example, a croconium dye can be produced by subjecting croconic acid to a condensation reaction with N, N-dialkylaniline, a heterocyclic active methylene compound, 2- (N, N-dialkylamino) thiophene, or the like. It is also possible to produce a croconium dye from croconic acid or a salt thereof using other methods known to those skilled in the art. Furthermore, methods known to those skilled in the art can be combined as appropriate to produce useful compounds other than croconium dyes.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
Manganese dioxide (IV) (250 g) was added in portions at room temperature while stirring to a water (3 L) solution of 2,3,5,6-tetrahydroxy-1,4-benzoquinone (100 g) and potassium carbonate (300 g). The reaction mixture was heated to reflux for 2 hours. After the reaction mixture was cooled to 80 ° C., Celite was added and the reaction mixture was filtered to remove insoluble components. The filtrate was cooled to 5 ° C., and the precipitated crystals were collected by filtration and washed with methanol to obtain dipotassium croconic acid as wet crystals. IR spectrum data of croconic acid dipotassium salt obtained by drying a part of this crystal was as follows.
IR νmax (KBr) 1741 (w), 1663 (m), 1529 (br, vs), 110 (w) cm ^-1
The entire amount of dipotassium croconic acid obtained by the above operation was suspended in methanol (800 mL), concentrated hydrochloric acid (100 mL) was added, and the reaction mixture was heated to reflux for 1 hour. As time passed, yellow potassium croconate dissolved and white potassium chloride precipitated. After cooling the reaction mixture to 45 ° C., the precipitated potassium chloride was removed by filtration, and the filtrate was concentrated to obtain 56 g of croconic acid as ocher crystals.
IR νmax (KBr) 3431 (br, m), 3300-2200 (br.s), 1757 (s), 1720 (w), 1659 (s), 1533 (s), 1477 (s), 1323 (s) , 1232 (s), 1072 (s), 837 (m), 631 (w) cm ^-1

(Example 2)
According to the method described in Example 1, the reaction was performed using 2,3,5,6-tetrahydroxy-1,4-benzoquinone (100 g), sodium carbonate (300 g), manganese dioxide (IV) (250 g), Croconic acid sodium salt was obtained as wet crystals.
The total amount of sodium croconate obtained by the above operation was suspended in methanol (1 L), an ion exchange resin Amberlite IR120B (proton type) manufactured by Organo Corporation was added, and the reaction mixture was heated to reflux for 1 hour. After the reaction mixture was cooled to 50 ° C., the resin was removed by filtration, the filtrate was concentrated, and the residue was dried to obtain 57.5 g of croconic acid as ocher crystals. The IR spectrum was consistent with that of croconic acid obtained in Example 1.
The recovered ion exchange resin could be easily regenerated and reused by a conventional technique in the art, for example, by washing after acid treatment.

(Comparative Example 1)
Croconic acid was synthesized by a method via barium croconate in accordance with the method described in Non-Patent Document 4. Manganese dioxide (IV) (300 g) was added in portions at room temperature while stirring to a water (6 L) solution of 2,3,5,6-tetrahydroxy-1,4-benzoquinone (100 g) and potassium carbonate (400 g). The reaction mixture was heated to reflux for 2 hours. After cooling the reaction mixture to 70 ° C., celite was added, and the reaction mixture was filtered to remove insoluble components. Concentrated hydrochloric acid was added to the filtrate to neutralize it to pH 2, and then saturated barium chloride aqueous solution was added to precipitate golden crystals. The reaction mixture was heated to reflux for 2 hours and then cooled to room temperature. The precipitated crystals were collected by filtration and washed with methanol to obtain barium croconate as wet crystals.
The total amount of barium croconate obtained by the above operation was suspended in methanol (1 L), 1.5 mol / L sulfuric acid (200 mL) was added, and the reaction mixture was heated to reflux for 1 hour. Due to the barium sulfate precipitated in this process, the fluidity of the reaction mixture was considerably deteriorated. The reaction mixture was cooled to 25 ° C. and filtered to remove barium sulfate, but the filterability was poor and the operation was difficult. The filtrate was concentrated and the residue was dried to obtain 52 g of croconic acid as ocher crystals.

  According to the production method of the present invention, a croconic acid compound can be produced safely and economically on an industrial scale. Since croconic acid is a common intermediate that is the key to the synthesis of croconium dyes, the production method of the present invention is useful for providing useful compounds and has high industrial applicability.

Claims (5)

The manufacturing method of the croconic acid compound characterized by including the following process.
(Step 1) A step of oxidizing tetrahydroxybenzoquinone in the presence of an inorganic base containing an alkali metal,
(Step 2) Step of precipitating an alkali metal croconate as a crystal by crystallization from the obtained reaction product, and
(Step 3) A step of isolating the alkali metal croconic acid salt by solid-liquid separation   The method according to claim 1, wherein the inorganic base containing an alkali metal is selected from the group consisting of an alkali metal hydroxide, an alkali metal alkoxide, an alkali metal carbonate, and an alkali metal bicarbonate. .   The inorganic base containing the alkali metal is sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate and potassium hydrogen carbonate. The manufacturing method according to claim 1, wherein the manufacturing method is selected from the group consisting of:   The manufacturing method according to any one of claims 1 to 3, wherein a transition metal oxide is used as an oxidizing agent in the (Step 1).   The manufacturing method according to any one of claims 1 to 3, wherein manganese (IV) is used as an oxidizing agent in the (step 1).