MXPA00004990A - Method for separating contaminants from 3-(2'-acetoxy-ethyl-dihydro-2(3h)furanone - Google Patents

Abstract

The invention relates to a method for separating contaminants from 3-(2'-acetoxy-ethyl-dihydro-2(3H)furanone (I), whereby the 3-(2'-acetoxy-ethyl-dihydro-2(3H)furanone containing the undesired contaminants is first produced using known methods by acetylization of 3-(2'-hydroxy-ethyl-dihydro-2(3H)furanone and is subsequently treated with strong mineral acids. Finally, the decomposition products of the undesired contaminants of (I) are separated.

Description

ELIMINATION OF IMPURITIES FROM 3- (2'- ACETOXYETHYL) DIHYDRO-2 (3H) -FURMTONA The present invention relates to a process for removing undesirable impurities of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone of the formula I. 3- (2'-Acetoxyethyl) dihydro-2 (3H) -furanone is an initial material for preparing methyl tetrahydropyran-4-carbsxylate, which in turn is an intermediate in the preparation of agents for the protection of crops. 3- (2'-Acetoxyethyl) dihydro-2 (3H) -furanone is prepared, for example, by processes that are known per se and are described, for example, in US-A 5,350,863, starting from methyl acetoacetate and ethylene oxide. Another variant of the process by which 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone is described in Dokl. Akad. Nauk SSSR 21_ (1940), 956-959 and US-A 5,283,326. In both variants, the desired 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone is formed as a mixture with an undesirable number of by-products, in particular dihydro-3- (2-methyl-1, 3 -dioxolan-2-yl) - (3H) -furanone II isomeric.

If the compound I contaminated in this way is reacted in a gas / continuous phase reaction, with methanol in the presence of acid catalysts to obtain methyl tetrahydropyran-4-carboxylate, considerably lower yields and shorter catalyst times are obtained in the compared to when a high purity product is used without the by-products. This is probably due to the fact that most of the by-products contain acetal groups which decompose on the catalyst surface in oligomeric and polymeric products. The removal by distillation of II in particular from the mixtures containing I and II can be carried out only with difficulty and at a high cost, due to the boiling points, which is very expensive. An object of the present invention is to provide a process by which undesirable byproducts, in particular II, can be removed from mixtures with I without changing I in the process. We have found that this goal is achieved by a process to remove impurities from 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone (I), which consists of initially preparing 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone containing the undesirable impurities in a manner known per se by acetylation of 3- (2'-hydroxyethyl) dihydro-2 (3H) -furanone, subsequently treating it with strong mineral acids and finally eliminating the decomposition products of the undesirable impurities from I. Surprisingly, the desired compound I is not degraded during the treatment with mineral acids and therefore can be obtained in good yield and high purity. Preferred embodiments of the process according to the invention are described in the sub-clauses and the following description. The process according to the invention begins with the mixture of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone and undesirable impurities which can be obtained by known processes which were described in the introduction. This mixture is initially acetylated in as complete a form as possible. Preferred acetylating agents are acetic anhydride or acetic acid itself; in principle, however, all the acetylating agents known to those skilled in the art are suitable for the corresponding acetylations. The acetylation is carried out, generally, at temperatures in the range of 40 ° C to 2'00 ° C, preferably from 60 to 140 ° C, during a period from 0.5 to 10, preferably from 0.8 to 5 and in particular from 1 to 3 hours. To ensure complete acetylation, the acetylating agent is generally employed in a molar excess of 5 to 50%, preferably 5 to 20%, based on 3- (2'-hydroxyethyl) dihydro-2 (3H) - furanone present in the mixture. In the subsequent step, the acetylation product is treated with strong mineral acids. The preferred mineral acids are hydrochloric acid, nitric acid and, particularly preferably, sulfuric acid. This is preferably used at a concentration of at least 80% and in particular in the form of concentrated sulfuric acid. The amount of sulfuric acid used can vary within wide ranges; in some cases, it was found convenient to use a molar ratio of strong mineral acid, based on the amount of the acetylating agent used in the previous step, in the range from 1:20 to 1: 3, preferably from 1:15 to 1 : 7 and, in particular, from 1: 8 to 1:12. For the treatment with the mineral acid, the temperature is generally in the range from 10 to 80, preferably from 20 to 60 and in particular from 30 to 50 ° C. The duration of the treatment is generally in the range from 0.3 to 10, in particular from 1 to 5 hours, but in principle, it can vary within wide limits.

After treatment with strong mineral acids, the products of the decomposition of unwanted impurities, in particular of dihydro-3- (2-methyl-l, 3-dioxolan-2-yl) -2 (3H) -furanone II they can be eliminated in a simple way. According to a preferred variant, the mineral acid is initially neutralized by the addition of base / preferably aqueous alkali metal hydroxide, and the acetic acid formed as co-product in the acetylation subsequently / if appropriate, is distilled. The separation of ~ phases is then carried out by the addition of a. suitable organic solvent and water, and the organic phase is then extracted. Suitable organic solvents are in particular aromatic hydrocarbons and especially alkylated benzene derivatives, such as xylene or toluene, the organic extracts are combined and the solvent is removed, and the residue can then be rectified under reduced pressure, providing, in good yield and high purity, the desired product that can later be further processed. The degree of purity of I can be further increased by carrying out more than one rectification in succession. The conditions for rectification are known per se to those skilled in the art and are described in the literature, so that no further details are required herein. After the process according to the invention has been carried out, the purity of I is generally at least 98%, preferably at least 98.5 and particularly preferably at least 99% by weight. The compound I obtainable by the process according to the invention can be reacted in a manner known per se with high yield and good catalyst times in stream to obtain methyl tetrahydropyran-4-carboxylate. This is an important intermediary in the preparation of agents for the protection of crops.

Example 1 (Comparison) In a 3.5 1 [sic] pressure vessel, a mixture of 1009 g (8.7 mol) of methyl acetoacetate, 1218 ml (969 g) of methanol and 110 g (0.61 mol) of a 30% strength solution of Sodium methoxide in methanol was initially charged, and 765.6 g (17.4 mol) of ethylene oxide were subsequently pumped at 60 ° C with stirring-over a period of 8 hours. The mixture was then stirred at 60 ° C, for 24 hours. The reaction discharge was repeatedly flooded with nitrogen and then transferred to an agitated apparatus having a column attached. The catalyst was then neutralized by the addition of 29.6 g (0.3 mol) of sulfuric acid (96%). The low-boiling components / mainly methanol, methyl acetate and methyl glycol were distilled at 10 mbar (1013 Pa) to a lower temperature of 100 ° C. At 100 ° C, 806 g (7.9 mol) of acetic anhydride were added over a period of one hour with stirring to the distillation residue, and the mixture was then stirred at 100 ° C for 2 hours. The excess acetic anhydride and acetic acid formed as a co-product during acetylation were subsequently distilled, and the crude discharge was cooled. After the addition of 726 g of toluene and 300 g of water, the phases were separated and the aqueous phase was extracted twice with 200 ml of toluene each time. The organic extracts were combined and the solvent was purified under reduced pressure using a rotary evaporator. The residue was rectified in batches under reduced pressure at 10 mbar (boiling point 161 ° C / 10 mbar). This produced 1077 g (72%) of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone (100% calculated).

Composition: 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone: 95.0% dihydro-3- (2-methyl-l, 3-dioxolan-2-yl) -2- (3H) -furanone: 3.5 % 3- (2 r -hydroxyethyl) dihydro-2 (3 H) -furanone: - 0.50% others: 1.0% Example 2 (A single rectification in batches) In a 3.5 1 [sic] pressure vessel, a mixture of 1009 g (8.7 mol) of methyl acetoacetate, 1218 ml (969 g) of methanol and 110 g (0.61 mol) of a solution at 30% concentration of methoxide in methane [sic] was initially charged, and 765.6 g (17.4 mol) of ethylene oxide were subsequently pumped to 60 ° C with shaking for a period of 8 hours. The mixture was then stirred at 60 ° C, for 24 hours. The reaction discharge was repeatedly flooded with nitrogen and then transferred to an agitated apparatus having a column attached. The catalyst was then neutralized by the addition of 29.6 g (0.3 mol) of sulfuric acid (96%). The low-boiling components, mainly methanol, methyl acetate and methyl glycol, were distilled at 10 mbar to a lower temperature of 100 ° C. At 100QC, 806 g (7.9 mol) of acetic anhydride were added during a period of one hour to the distillation residue, and the mixture was then stirred at 100 ° C for 2 h. To decompose dihydro-3- (2-methyl-1, 3-dioxolan-2-yl) -2 (3H) -furanone, the reaction mixture was cooled to 40 ° C, 72.5 g (0.73 mol) of sulfuric acid (96%) were added - and the mixture was then stirred at this temperature for 2 hours. To neutralize the sulfuric acid, 127.5 g (1.59 mol) of NaOH at 50% concentration were subsequently added at 40-45 ° C. The acetic acid that formed as a ce-product during acetylation was distilled and the crude discharge was cooled. After the addition of 726 g of toluene and 850 g of water, the phases were separated and the aqueous phase was extracted twice with 200 ml of toluene each time. The organic extracts were combined and the solvent was distilled under reduced pressure using a rotary evaporator. The residue was rectified in batches under reduced pressure at 100 mbar (boiling point 161 ° C / 10 mbar). This produced 1056 g (71%) of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone (100% calculated).

Composition: 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone: 98.5% dihydro-3- (2-methyl-l, 3-dioxolan-2-yl) -2- (3H) -furanone: 0.3 % 3- (2'-Hydroxyethyl) dihydro-2 (3H) -furanone: 0.3% other: 0.9% Example 3 (Triple continuous rectification) In a pressure vessel of 1 m, a mixture of 348 kg (3.0 kmol) of methyl acetoacetats, 420.1 1 (334.2 kg) of methanol and 37.9 kg (210.3 mol) of a solution at 30% concentration of sodium methoxide in methanol was initially charged and 264.1 kg (6.0 k ol) of Ethylene oxide were subsequently pumped with agitation at 60 ° for a period of 8 hours. The mixture was then stirred at 60 ° C, for 24 hours. The reaction was flushed repeatedly with nitrogen and then transferred to a stirred apparatus of 1 m 3 [sic] having a column attached. The catalyst was then neutralized by the addition of 10.2 kg (103.5 mol) of sulfuric acid (96%). The low-boiling components, mainly methanol, methyl acetate and methyl glycol, were distilled to 10 steal (1013 Pa) to a waste temperature of 100 ° C. At 100 ° C, 278 kg (2.7 kmol) of acetic anhydride were added with stirring for a period of one hour to the residue of the distillation, and the mixture was then stirred at 100 ° C for 2 hours. To decompose dihydro-3- (2-methyl-1, 3-dioxolan-2-yl) -2 (3H) -furanone, the reaction mixture was cooled to 40 ° C, 25.0 kg (251.8 mole) of sulfuric acid (96%) were added and the mixture was then stirred at this temperature for 2 hours. To neutralize the sulfuric acid, 439.7 kg (548 mol) of NaOH at 50% concentration were subsequently added at 40-45 ° C. The acetic acid formed as a co-product during acetylation was distilled, and the crude discharge was cooled. After the addition of 250.4 kg of toluene and 293.2 kg of water, the phases were separated and the aqueous phase was extracted twice with 100 kg of toluene each time. The organic extracts were combined and processed further. This gave 375.3 kg (73%) of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone (100% calculated).

Composition: 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone: 99.5% dihydro-3- (2-methyl-1,3-dioxolan-2-yl) -2- (3H) -furanone: < 0.1% " 3- (2'-Hydroxyethyl) dihydro-2 (3H) -furanone: 0.3% other: 0.1% To investigate the effects of the degree of purity of I in the subsequent reaction, the products obtained by the Examples 1 to 3 were converted to methyl tetrahydropyran-4-carboxylates according to the following general equation: Per hour, a solution containing 172 g of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone and 192 g of methanol was evaporated and passed to a tubular reactor at 250 ° C on 2000 g of an oxide catalyst. of? -aluminum (Pural SB ™, formed in 2 mm strands, dried for 16 h at 120 ° C and calcined for 3 h at 520 ° C). The gaseous reaction discharge was condensed and the resulting terahydropyran-4-carboxylate ester was purified by distillation in batches (boiling point 117 ° C / 30 mbar). The results of the reactions of 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone I with different proportions of dihydro-3- (2-methyl-l, 3-dioxolan-2-yl) -2 (3H ) - furanone II are summarized in Table 1: Table 1: The results of the previous table show the strong effect of the content of impurities, in particular II, on the other processing of I.

Claims (3)

1. REI INDICATIONS
2. A process for removing impurities from 3- (2'-acetygxyethyl) dihydro-2 (3H) -furanone (I), which consists initially of preparing 3- (2'-acetoxyethyl) dihydro-2 (3H) -furanone containing the undesirable impurities in a manner known per se by acetylating
3. 3- (2'-hydroxyethyl) dihydro-2 (3H) -furanone, subsequently treating it with strong mineral acids and finally eliminating the decomposition products of the unwanted impurities of I. The process as recited in claim 1, wherein the acetylating agent used is acetic anhydride or acetic acid. The process as mentioned in any of claims 1 or 2, wherein the strong mineral acid used is sulfuric acid. The process as mentioned in any of claims 1 to 3, wherein the treatment with sulfuric acid is carried out at temperatures from 20 to 70 ° C. The process as mentioned in any of claims 1 to 4, wherein the decomposition products are removed by phase separation, subsequent extraction and distillation or rectification. The process as mentioned in any of the claims [lacuna] 5, where distillation or rectification is carried out in multiple steps.