KR19980015530A - Preparation method of 2,6-dihydroxybenzoic acid - Google Patents
Preparation method of 2,6-dihydroxybenzoic acid Download PDFInfo
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- KR19980015530A KR19980015530A KR1019960034895A KR19960034895A KR19980015530A KR 19980015530 A KR19980015530 A KR 19980015530A KR 1019960034895 A KR1019960034895 A KR 1019960034895A KR 19960034895 A KR19960034895 A KR 19960034895A KR 19980015530 A KR19980015530 A KR 19980015530A
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- C07C51/10—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide
- C07C51/12—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide on an oxygen-containing group in organic compounds, e.g. alcohols
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- C07C65/00—Compounds having carboxyl groups bound to carbon atoms of six—membered aromatic rings and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups
- C07C65/01—Compounds having carboxyl groups bound to carbon atoms of six—membered aromatic rings and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups containing hydroxy or O-metal groups
- C07C65/03—Compounds having carboxyl groups bound to carbon atoms of six—membered aromatic rings and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups containing hydroxy or O-metal groups monocyclic and having all hydroxy or O-metal groups bound to the ring
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Abstract
디히드록시 방향족 화합물에 보호기를 도입하고, 고압의 이산화탄소 가스가 채워진 반응 용기 내에서 보호기로 치환된 디히드록시 방향족 화합물을 물과 유기 용매에 용해시켜 반응시켜 2,6 디히드록시 벤조산을 제조하는 방법은, 부산물인 2,4 디히드록시 벤조산이 생성되는 반응 사이트의 활성을 약화시켜 그 생성을 막아 최종 물질 정제시 분리공정을 거치지 않아도 되며, 유기 용매가 촉매 역할을 하여 반응성을 증대시킴에 따라 고수율로 2,6 디히드록시 벤조산을 제조할 수 있는 새로운 방법이다.Dihydroxybenzoic acid is prepared by introducing a protecting group into a dihydroxyaromatic compound and dissolving a dihydroxyaromatic compound substituted with a protecting group in a reaction vessel filled with high-pressure carbon dioxide gas in water and an organic solvent to obtain a dihydroxybenzoic acid , The activity of the reaction site in which 2,4-dihydroxybenzoic acid is produced as a by-product is weakened to inhibit the production thereof, thereby eliminating the separation step in the purification of the final material and increasing the reactivity of the organic solvent as a catalyst Dihydroxybenzoic acid can be prepared at a high yield.
Description
본 발명은 2,6 디히드록시 벤조산에 관한 것으로서, 더욱 상세하게는 고순도, 고수율로 2,6 디히드록시 벤조산을 제조하는 방법에 관한 기술이다.The present invention relates to 2,6-dihydroxybenzoic acid, and more particularly, to a process for producing 2,6-dihydroxybenzoic acid at a high purity and a high yield.
디히드록시 벤조산은 의약, 염료, 자외선 안정제의 중간 제품으로서 널리 사용되고 있는 물질로서, 이와 같은 디히드록시 벤조산은 일반적으로 레조시놀의 카르복실화 반응에 의해 제조된다. 이때 생성물은 2,6 디히드록시 벤조산과 2,4 디히드록시 벤조산의 두 개의 이성체의 혼합물의 형태로 나타난다. 그러나 최근 2,6 디히드록시 벤조산의 사용범위가 넓어져 그 수요가 2,4 디히드록시 벤조산의 수요보다 증가되고 있으며 또 높은 순도를 요구하고 있다.Dihydroxybenzoic acid is widely used as an intermediate product of medicines, dyes and ultraviolet stabilizers. Such dihydroxybenzoic acid is generally prepared by the carboxylation reaction of resorcinol. Where the product appears in the form of a mixture of two isomers of 2,6 dihydroxybenzoic acid and 2,4 dihydroxybenzoic acid. However, recently, the use range of 2,6-dihydroxybenzoic acid has widened and the demand thereof has been increasing more than the demand of 2,4-dihydroxybenzoic acid, and a high purity is required.
이에 따라 2,6 디히드록시 벤조산을 제조하기 위해서는 상기와 같은 방법으로 제조된 디히드록시 벤조산 이성체 혼합물로부터 2,6 디히드록시 벤조산을 분리하여 사용하고 있다.Thus, in order to prepare 2,6-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid is separated from the dihydroxybenzoic acid isomer mixture prepared by the above-mentioned method.
디히드록시 벤조산 이성체의 혼합물에서 2,6 디히드록시 벤조산을 분리하는 방법으로서 일본국 공개 특허 평62-440호에는, 2,6 디히드록시 벤조산이 50%이상 포함되어져 있는 알칼리 분위기인 디히드록시 벤조산 이성체 혼합물을 산으로 중화하여 pH를 4로 맞춘 후 녹지 않고 침전으로 떨어진 물질을 제거하고, 그 용액을 pH=1로 맞춘 후 생성된 침전을 여과하고 최종 물질을 얻는 기술이 개시되어 있다.As a method for separating 2,6 dihydroxybenzoic acid from a mixture of dihydroxybenzoic acid isomers, Japanese Patent Application Laid-Open No. 62-440 discloses a method for separating 2,6 dihydroxybenzoic acid from dihydroxybenzoic acid, which is an alkali atmosphere containing 2,6 dihydroxybenzoic acid in an amount of 50% A technique for neutralizing a mixture of a hydroxybenzoic acid isomer with an acid to adjust the pH to 4, removing a substance which has not dissolved and precipitating, removing the precipitate, adjusting the pH of the solution to pH = 1, and filtering the resulting precipitate to obtain a final product.
또한 GB-A-916,548에는 알카리 용액안의 디히드록시 벤조산 혼합물을 염산으로 산성화하여 2,6 디히드록시 벤조산을 얻고, 이 물질을 75 ℃의 물에 다시 녹인 후 녹지 않는 물질을 제거하고 이 용액을 냉각하면 순수한 2,6 디히드록시 벤조산이 얻어짐이 개시되어 있다.In GB-A-916,548, a dihydroxybenzoic acid mixture in an alkaline solution is acidified with hydrochloric acid to obtain 2,6-dihydroxybenzoic acid. This material is again dissolved in water at 75 ° C, and the insoluble material is removed. It is disclosed that pure 2,6 dihydroxybenzoic acid is obtained by cooling.
상기와 같은 방법들은 pH value를 조절함으로써 알카리용액 속의 디히드록시 벤조산 이성체의 혼합물로부터 2,6 디히드록시 벤조산과 2,4 디히드록시 벤조산을 분리하는 기술이다. 그러나 위의 방법들에 의해서 얻어지는 2,6 디히드록시 벤조산은 2,4 디히드록시 벤조산에 의하여 쉽게 오염될 수 있으므로 고순도의 2,6 디히드록시 벤조산을 얻기 어렵다는 문제점이 있으며 또한 카르복실화 반응에 의해 생성되는 결과 물이 2,6 디히드록시 벤조산과 2,4 디히드록시 벤조산의 혼합물임으로 2,6 디히드록시 벤조산의 제조 수율이 낮다는 문제점 있다.Such methods are a technique for separating 2,6 dihydroxybenzoic acid and 2,4 dihydroxybenzoic acid from a mixture of dihydroxybenzoic acid isomers in an alkaline solution by adjusting the pH value. However, 2,6-dihydroxybenzoic acid obtained by the above methods can be easily contaminated by 2,4-dihydroxybenzoic acid, so that it is difficult to obtain 2,6-dihydroxybenzoic acid of high purity. Also, Is a mixture of 2,6 dihydroxybenzoic acid and 2,4 dihydroxybenzoic acid, the production yield of 2,6 dihydroxybenzoic acid is low.
본 발명은 상기와 같은 종래 기술의 문제점을 해결하기 위하여 개발된 것으로서, 본 발명의 목적은 부산물인 2,4 디히드록시 벤조산의 생성을 억제하여 고수율로 2,6 디히드록시 벤조산을 제조하는 방법을 제거하고, 아울러 2,6 디히드록시 벤조산을 고순도로 분리할 수 있는 벤조산의 분리 방법을 제공한다.Disclosure of the Invention The present invention has been developed in order to overcome the problems of the prior art as described above, and an object of the present invention is to provide a process for producing 2,6-dihydroxybenzoic acid at a high yield by inhibiting the production of 2,4-dihydroxybenzoic acid, And separating the 2,6-dihydroxybenzoic acid in high purity. The present invention also provides a method for separating benzoic acid.
상기와 같은 본 발명의 목적을 달성하기 위하여 본 발명은, 알콕시 금속염 용액 내에서 레조시놀과 알킬 아세토아세테이트류를 반응시켜 레조시놀에 보호기를 도입하는 공정과, 알카리 금속이 용해된 혼합 용매에 상기 보호기가 도입된 반응물을 첨가하고 이산화탄소 가스를 주입하여 보호기가 도입된 레조시놀을 카르복실화하는 공정과, 상기 카르복실화된 반응물로부터 보호기를 제거하는 공정을 포함하는 2,6 디히드록시 벤조산의 제조 방법을 제공한다.In order to accomplish the above object, the present invention provides a process for producing a metal complex, comprising the steps of reacting a resorcinol and an alkyl acetoacetate in an alkoxy metal salt solution to introduce a protecting group into the resorcinol, A step of adding a reactant into which the protecting group is introduced and introducing a carbon dioxide gas to carboxylate the resorcinol into which the protecting group is introduced and removing the protecting group from the carboxylated reactant, Benzoic acid.
상기한 본 발명에 있어서, 상기 알킬 아세토아세테이트류는 메틸 아세토 아세테이트, 에틸 아세토 아세테이트, 프로필 아세토 아세테이트로 이루어진 군에서 선택되는 것이 바람직하다. 그리고 상기 알콕시 금속염은 t-부톡시 나트륨, t-부톡시 칼륨, 에톡시 나트륨, 메톡시 나트륨으로 이루어진 군에서 선택되는 촉매로서, 레조시놀 1몰에 대하여 0.2∼3몰을 사용하는 것이 바람직하며, 상기 알카리 금속은 탄산칼슘, 수산화나트륨, 수산화칼슘, 탄산나트륨으로 이루어진 군에서 선택되는 것으로서, 레조시놀 1몰에 대하여 1∼4몰 사용하는 것이 바람직하다.In the present invention, the alkyl acetoacetates are preferably selected from the group consisting of methyl acetoacetate, ethyl acetoacetate, and propyl acetoacetate. The alkoxy metal salt is preferably selected from the group consisting of t-butoxy sodium, t-butoxy potassium, ethoxy sodium and methoxy sodium, and is preferably used in an amount of 0.2 to 3 mol based on 1 mol of resorcinol , And the alkali metal is selected from the group consisting of calcium carbonate, sodium hydroxide, calcium hydroxide, and sodium carbonate, and it is preferable to use 1 to 4 moles relative to 1 mole of resorcinol.
또 상기한 본 발명에 있어서, 상기 혼합용매는 물과 유기 용매의 혼합 용매로서, 상기 유기 용매는 X-(CH2)n-OH (여기서 X는 저급알콕시, n은 3∼6의 정수), 또는 CH3-(CH2)n-OH (여기서 n은 2∼5의 정수)이며, 상기 혼합용매에서 물과 유기용매의 무게비는 1:0.5∼0.05인 것이 바람직하다.In the present invention, the mixed solvent is a mixed solvent of water and an organic solvent, and the organic solvent is X- (CH 2) n -OH (wherein X is lower alkoxy, n is an integer of 3 to 6) CH3- (CH2) n-OH wherein n is an integer of 2 to 5, and the weight ratio of water to the organic solvent in the mixed solvent is preferably 1: 0.5 to 0.05.
그리고 상기한 본 발명에 있어서, 상기 카르복실화하는 공정은 CO2 가스 압력을 4기압 내지 30기압의 압력으로 공급하고 40 내지 190℃의 온도에서 실시하는 것이 바람직하다.In the present invention, it is preferable that the step of carboxylation is carried out at a temperature of 40 to 190 ° C by supplying a CO 2 gas pressure at a pressure of 4 atm to 30 atm.
또 본 발명은 상기 제조된 2,6 디히드록시 벤조산을 용매에 녹여 농축한 후 난용성 용매를 이용하여 재결정하여 2,6 디히드록시 벤조산의 순도를 높이는 공정을 더욱 포함하는 것이 바람직하다. 이 때 상기 용매로는 메탄올, 에탄올, 프로판올로 이루어진 군에서 선택되는 것이며, 상기 난용성 용매는 탄화수소류인 것이 바람직하다.Further, it is preferable that the present invention further comprises a step of dissolving 2,6 dihydroxybenzoic acid in a solvent, concentrating it, and then recrystallizing using a poorly soluble solvent to increase the purity of 2,6 dihydroxybenzoic acid. At this time, the solvent is selected from the group consisting of methanol, ethanol and propanol, and the poorly soluble solvent is preferably a hydrocarbon.
본 발명을 보다 상세하게 설명하면 다음과 같다.The present invention will be described in more detail as follows.
본 발명은 디히드록시 방향족 화합물의 카르복실화에 의하여 부산물로 2,4 디히드록시 벤조산이 생성되는데 디히드록시 방향족 화합물에 보호기를 도입하여 부산물인 2,4 디히드록시 벤조산이 생성되는 반응사이트의 활성을 약화시켜 그 생성을 막아 최종 물질 정제시 분리공정을 거치지 않도록 한 것이며, 또 고압의 이산화탄소 가스가 채워진 반응 용기 내에서 보호기로 치환된 디히드록시 방향족 화합물을 물과 유기 용매에 용해시켜 반응시킴으로서 유기 용매가 촉매 역할을 하여 반응성을 증대시킴에 따라 고수율로 2,6 디히드록시 벤조산의 새로운 제조방법에 관한 것이다. 또 본 발명에 따라 제조된 2,6 디히드록시 벤조산을 난용성용매(nonsolvent)를 사용하여 용해도 차이를 이용하여 부산물과 목표 물질을 효과적으로 분리하여 고순도의 2,6 디히드록시 벤조산을 제조하는 것이다.In the present invention, 2,4-dihydroxybenzoic acid is produced as a by-product by the carboxylation of a dihydroxyaromatic compound, and a reaction site in which 2,4-dihydroxybenzoic acid, which is a byproduct, is produced by introducing a protecting group into the dihydroxyaromatic compound The reaction is carried out by dissolving the dihydroxyaromatic compound substituted with a protecting group in water and an organic solvent in a reaction vessel filled with carbon dioxide gas at a high pressure, To a new process for preparing 2,6-dihydroxybenzoic acid in high yield by increasing the reactivity of the organic solvent as a catalyst. Further, 2,6 dihydroxybenzoic acid prepared according to the present invention is effectively separated from the by-products and the target materials by using a difference in solubility using a nonsolvent to prepare 2,6 dihydroxybenzoic acid of high purity .
본 발명의 대표적인 실시예는 다음과 같다.A representative embodiment of the present invention is as follows.
레조시놀과 알카리염을 물에 용해시킨 후 알킬 아세토아세테이트류의 물질을 투입하고 약 50 내지 100℃ 온도로 가열하여 부산물이 생길 수 있는 반응 사이트의 반응성을 떨어뜨리는 보호기를 도입한다. 그런 후 교반기가 부착되어 있는 고압반응기에 위의 반응 물질과 콜베-쉬미트 반응에 사용되는 알카리 금속염을 물과 유기 용매(무게비 9:1)를 섞은 혼합 용매와 함께 투입한 후, 이산화탄소 가스를 4내지 30기압으로 채우고 120 내지 190℃의 온도로 가열하여 3 내지 7시간 반응시킨 후 감압 증류하여 유기용매를 제거하고 30 ℃ 이하로 냉각한다. 여기에 산을 적가하여 디히드록시 벤조산염을 산성화하면 침전물이 생성된다. 이 물질은 보호기가 붙어 있으므로 보호기를 제거하기 위하여 수산화나트륨이 녹아있는 물에 투입하여 3 내지 5시간 환류시킨후 산으로 다시 산성화시키면 최종 물질인 2,6 디히드록시 벤조산이 생성된다. 최종 물질의 순도를 높이기 위하여 생성된 물질을 알코올에 녹여 농축시킨 후 탄화수소류의 용매를 투입하여 고순도의 2,6 디히드록시 벤조산을 제조한다.Resorcinol and an alkali salt are dissolved in water, alkyl acetoacetate is added thereto, and the reaction is heated at a temperature of about 50 to 100 ° C. to introduce a protecting group which lowers the reactivity of the reaction site where byproducts may occur. Then, the above reactant and the alkali metal salt used in the Kolbe-Schmid reaction were added to a high-pressure reactor equipped with a stirrer together with a mixed solvent of water and an organic solvent (weight ratio 9: 1). Then, To 30 atm. The reaction mixture is heated at a temperature of 120 to 190 ° C and reacted for 3 to 7 hours. The reaction mixture is distilled under reduced pressure to remove the organic solvent and cooled to 30 ° C or less. Acidification of the dihydroxybenzoate by dropwise addition of acid thereto produces a precipitate. Since this material has a protecting group, it is added to water in which sodium hydroxide is dissolved to remove the protecting group, and after refluxing for 3 to 5 hours, acidification with acid again results in 2,6 dihydroxybenzoic acid as a final product. In order to increase the purity of the final material, the resulting material is dissolved in alcohol and concentrated, and then a hydrocarbon solvent is added thereto to produce high purity 2,6-dihydroxybenzoic acid.
상기 본 발명에 사용되는 용매로는 물과 유기 용매의 혼합 용매이며, 유기 용매로는 알코올, 알콕시 알코올, 그리고 디메틸 포름아마이드을 사용할 수 있다. 이 때 유기 용매는 일반적으로 디히드록시 방향족 화합물에 대해서 0.5에서 10배를 사용한다. 사용하는 알카리금속염으로는 탄산칼슘, 수산화나트륨, 수산화칼륨, 탄산나트륨 등이며 디히드록시 방향족 화합물의 1에서 4배를 사용한다.The solvent used in the present invention is a mixed solvent of water and an organic solvent, and examples of the organic solvent include alcohols, alkoxy alcohols, and dimethyl formamide. In this case, the organic solvent is generally used in an amount of 0.5 to 10 times with respect to the dihydroxy aromatic compound. As the alkali metal salt to be used, calcium carbonate, sodium hydroxide, potassium hydroxide, sodium carbonate and the like are used, and 1 to 4 times of the dihydroxy aromatic compound is used.
이하 본 발명의 바람직한 실시예를 기재한다. 그러나 하기한 실시예는 본 발명의 이해를 돕기 위한 본 발명의 바람직한 일 실시예일 뿐 본 발명이 하기한 실시예에 한정되는 것은 아니다.Hereinafter, preferred embodiments of the present invention will be described. However, the following embodiments are merely preferred embodiments of the present invention in order to facilitate understanding of the present invention, and the present invention is not limited to the following embodiments.
실시예 1Example 1
1L 삼구둥근플라스크에 28중량% 메톡시 나트륨 용액 100g(0.52몰)을 넣고 교반하면서 레조시놀 95g(0.86몰)을 투입하고 완전히 용해시켰다. 교반시 질소를 서서히 불어주면서 여기에 에틸 아세토아세테이트 103g(0.79몰)을 천천히 투입한 후 반응 온도를 80℃로 하여 10시간동안 가열하였다. 반응 종료후 반응물을 50℃로 냉각하여 35중량% 염산 50g과 물 100g을 혼합하여 천천히 적가하면 연노랑색 고체가 침전이 생성되었다. 이 고체를 건조하여 4-메틸-7-히드록시 큐마린 128g(수율:85%)를 얻었다.100 g (0.52 mol) of a 28 wt% methoxysodium solution was added to a 1 L three-neck round flask, and 95 g (0.86 mol) of resorcinol was added while stirring to completely dissolve. 103 g (0.79 mol) of ethyl acetoacetate was slowly added thereto while slowly stirring nitrogen while stirring, and the reaction temperature was raised to 80 ° C for 10 hours. After completion of the reaction, the reaction product was cooled to 50 캜, and 50 g of 35% by weight hydrochloric acid and 100 g of water were mixed. When the mixture was slowly dropped, a pale yellow solid precipitated. This solid was dried to obtain 128 g (yield: 85%) of 4-methyl-7-hydroxyquimarnine.
온도계, 리본 형태의 교반기가 부착되어 있는 500ml의 고압반응기에 150ml의 물과 40ml의 에탄올을 투입한 후 질소로 1시간동안 불어주었다. 그런 후 4-메틸-7-히드록시 큐마린 128g(0.73몰)과 탄산칼륨 96.6g(0.7몰)을 투입하고 반응기를 밀폐시킨 후 160℃로 승온하였다. 그리고 반응기에 이산화탄소가스 압력이 15기압이 되도록 유지하며 4시간 반응시키고, 반응 종료후 30℃로 교반하면서 냉각하였다. 여기에 물을 50g가량 첨가한 후 30중량% 염산 200g을 2시간 동안 적가하면 침전이 생성되고 이 고체를 여과하여 다시 300g의 물에 용해시키고 30중량% 수산화나트륨386g(2.92몰) 용액을 적가한 후 5시간 동안 환류하였다. 그리고 20℃로 냉각후 35중량%염산을 적가하여 pH=1로 맞추었다. 그러면 흰색고체인 2,6 디히드록시 벤조산 83g(0.54몰, 수율:63%)를 얻었다.150 ml of water and 40 ml of ethanol were added to a 500 ml high-pressure reactor equipped with a thermometer and a ribbon-type stirrer, and then the mixture was blown with nitrogen for 1 hour. Thereafter, 128 g (0.73 mole) of 4-methyl-7-hydroxyquimarnine and 96.6 g (0.7 mole) of potassium carbonate were charged and the reactor was sealed and then heated to 160 ° C. The reaction was continued for 4 hours while keeping the pressure of the carbon dioxide gas at 15 atm in the reactor. After completion of the reaction, the reaction mixture was cooled with stirring at 30 캜. 50 g of water was added thereto, and 200 g of 30% by weight hydrochloric acid was added dropwise for 2 hours to form a precipitate. The solid was filtered off again and dissolved in 300 g of water, and a solution of 386 g (2.92 mol) of 30 wt% sodium hydroxide was added dropwise And refluxed for 5 hours. After cooling to 20 캜, 35% by weight hydrochloric acid was added dropwise to adjust pH = 1. 83 g (0.54 mol, yield: 63%) of 2,6-dihydroxybenzoic acid as white solid was obtained.
실시예 2Example 2
1L 삼구둥근플라스크에 28중량% 메톡시 나트륨 용액 120g(0.62몰)을 넣고 교반하면서 레조시놀 112g(1.02몰)을 투입하고 완전히 용해시켰다. 교반시 질소를 서서히 불어주면서 여기에 메틸 아세토아세테이트 106g(0.94몰)을 천천히 투입한 후 반응온도를 80℃로하여 10시간동안 가열하였다. 반응 종료후 반응물을 50℃로 냉각하여 35중량% 염산 70g과 물 120g을 혼합하여 천천히 적가하면 연노랑색 고체가 침전이 생성되었다. 이 고체를 건조하여 4-메틸-7-히드록시 큐마린 154.9g(수율:86%)를 얻었다.120 g (0.62 mol) of a 28 wt% methoxysodium solution was added to a 1 L three-neck round flask, and 112 g (1.02 mol) of resorcinol was added while stirring to completely dissolve. 106 g (0.94 mol) of methyl acetoacetate was slowly added thereto while slowly stirring nitrogen while stirring, and then the reaction temperature was raised to 80 ° C for 10 hours. After completion of the reaction, the reaction product was cooled to 50 캜, 70 g of 35% by weight hydrochloric acid and 120 g of water were mixed. When the mixture was slowly dropped, a pale yellow solid precipitated. The solid was dried to obtain 154.9 g (yield: 86%) of 4-methyl-7-hydroxyquimarine.
온도계, 리본형태의 교반기가 부착되어 있는 500ml의 고압반응기에 200ml의 물과 20ml의 1-메톡시-2-프로판올을 투입한 후 질소로 1시간동안 불어주었다. 그런 후 4-메틸-7-히드록시 큐마린 154.9g(0.88몰)과 탄산칼륨 117g(0.85몰)을 투입하고 반응기를 밀폐시킨 후 175도로 승온하였다. 그리고 반응기에 이산화탄소가스 압력이 20기압이 되도록 유지하며 4시간 반응하였다. 반응 종료후 30℃로 교반하면서 냉각하였다. 여기에 물을 80g가량 첨가한 후 35중량% 염산 250g을 2시간 동안 적가하면 침전이 생성되고 이 고체를 여과하여 다시 350g의 물에 용해시키고 30중량% 수산화나트륨 462g(3.52몰) 용액을 적가한 후 5시간동안 환류하였다. 그리고 20℃로 냉각후 35중량% 염산을 적가하여 pH=1로 맞추었다. 그러면 흰색고체인 2,6 디히드록시 벤조산 100g(0.65몰, 수율:63%)를 얻었다. 그런 후 이 고체를 120g의 메탄올에 녹여 1시간동안 환류한 후 20도로 냉각하였다. 여기에 헥산 250g을 넣고 교반하여 흰색침전이 생성되고 이것을 여과하면 순도 99%이상인 2,6 디히드록시 벤조산 93g(수율:59%)를 얻었다.200 ml of water and 20 ml of 1-methoxy-2-propanol were added to a 500 ml high-pressure reactor equipped with a stirrer, a thermometer and a ribbon type stirrer, followed by blowing with nitrogen for 1 hour. Thereafter, 154.9 g (0.88 mol) of 4-methyl-7-hydroxyquimarine and 117 g (0.85 mol) of potassium carbonate were added, and the reactor was sealed. The reactor was maintained at a pressure of 20 atm for 2 hours and reacted for 4 hours. After completion of the reaction, the mixture was cooled with stirring at 30 캜. 80 g of water was added thereto, and 250 g of 35% by weight hydrochloric acid was added dropwise for 2 hours to form a precipitate. The solid was filtered and dissolved again in 350 g of water, and a solution of 462 g (3.52 mol) of 30% by weight sodium hydroxide was added dropwise And refluxed for 5 hours. After cooling to 20 캜, 35% by weight hydrochloric acid was added dropwise to adjust pH = 1. 100 g (0.65 mol, yield: 63%) of 2,6-dihydroxybenzoic acid as a white solid was obtained. The solid was then dissolved in 120 g of methanol and refluxed for 1 hour and then cooled to 20 degrees. To this was added 250 g of hexane and the mixture was stirred to form a white precipitate, which was filtered to obtain 93 g (yield: 59%) of 2,6 dihydroxybenzoic acid having a purity of 99% or more.
상기한 실시예에서 알 수 있는 바와 같이, 본 발명은 물과 유기용매를 혼합용매로 하여 유기 용매를 촉매로 사용하므로 반응의 평형조건을 개선하여 수율을 증대시켰으며 레조시놀에 보호기를 도입, 부산물의 생성을 억제하여, 언제나 단점으로 대두되어 왔던 레조시놀의 카르복실화에 의한 디히드록시 벤조산 이성체 혼합물에서 목표 물질을 분리하는 복잡하고 어려운 공정을 거치지 않아도 되는 우수한 2,6 디히드록시 벤조산의 제조 방법이다.As can be seen from the above examples, the present invention uses water and an organic solvent as a mixed solvent and uses an organic solvent as a catalyst, thereby improving the equilibrium condition of the reaction to increase the yield, introducing a protecting group into the resorcinol, It is an object of the present invention to provide a process for producing 2,6-dihydroxybenzoic acid, which is free from the complicated and difficult process of separating the target material from the dihydroxybenzoic acid isomer mixture by the carboxylation of the resorcinol, .
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