JPS6136813B2 - - Google Patents

Description

[Detailed description of the invention] The present invention is based on the general formula

[Formula] (R represents hydrogen or an alkyl group) 3-methyl-2 which is dehydrated and condensed with γ-methyl-γ-lactones
- Concerning a method for producing cyclopentenones. 3-Methyl-2-cyclopentenones are fragrances,
It has useful uses as a starting material for pharmaceuticals, agricultural chemicals, etc. Conventionally known methods for producing 2-cyclopentenones include the following. (1) Method of heating γ-lactone with phosphorus pentoxide [J.Am.Chem.Soc., 70, 1379, (1948)]. (2) Method of adding γ-lactone to a mixture of phosphorus pentoxide and phosphoric acid and heating it [J.Indian Chem.
Soc.34, 169-77 (1957)]. (3) A method in which γ-lactone is heated in the presence of a solid acid catalyst (Japanese Patent Publication No. 18493/1983). In method (1), the yield of 2-cyclopentenones is low, especially at the γ-position. In the case of γ-lactones whose alkyl group has a small number of carbon atoms, it is almost impossible to produce them.Method (2) has almost the same problems as (1).Method (3) has problems such as (1), ( Although the yield is improved compared to 2), it is still not sufficient, especially for γ-
If the number of carbon atoms in the alkyl group at position is small, the yield will be low, and the selectivity will be poor, resulting in several types of products, making purification complicated, and the reaction will be carried out at high temperatures, making the equipment complicated, etc. There is a problem. In order to solve the above problems, the present inventors first discovered that when condensed phosphoric acid is expressed as X・H ₂ O・y・P ₂ O ₅ , X/y=R is 1.5<R. We have found that 2-cyclopentenones can be produced in high yield from γ-lactones using condensed phosphoric acid with <2.7 as a catalyst. However, the condensed phosphoric acid incorporates water generated during the reaction, reducing its catalytic effect, so it must be used in large amounts relative to the γ-lactone.In addition, in order to recover the condensed phosphoric acid, The recovery process is complicated, as it requires dehydration of the aqueous layer containing the catalyst in two stages: heating under atmospheric pressure and heating under high vacuum, and is still not satisfactory. As a result of intensive research to solve this problem, we found that by using a solvent that is insoluble in water and inert to the reaction system, phosphoric acid and/or condensed phosphoric acid was added as a catalyst, and γ-methyl-γ- By heating the lactones to near the boiling point of the solvent and removing the generated water from the system together with the solvent, the reaction can proceed smoothly and 3-methyl-2-cyclopentenones are produced in high yield. In addition, we have found that the catalyst can be easily recovered by heating the aqueous layer containing the catalyst to near the boiling point of the solvent and removing water together with the solvent. That is, the present invention is based on the general formula

γ- represented by [Formula] (R represents hydrogen or an alkyl group)
By dehydrating and condensing methyl-γ-lactones, the general formula

When producing 3-methyl-2-cyclopentenones represented by the formula, phosphoric acid and/or condensed phosphoric acid is added in a solvent that does not dissolve the dehydration condensation in water and is inert to the reaction system. In addition, the method is characterized in that water generated by the reaction is removed from the system together with the solvent while heating the solvent to near its boiling point. The present invention will be specifically described in detail. The γ-methyl-γ-lactones used in the present invention are not particularly limited, but common examples include γ-methyl-γ-valerolactone, γ-methyl-γ-hexalactone, and γ-methyl-γ-heptalactone. , γ-methyl-γ-octalactone, γ
-Methyl-γ-nonalactone, γ-methyl-γ-
Decalactone, etc. In particular, γ-methyl-γ-
Regarding valerolactone, the yield is significantly improved compared to the conventional method. Examples of solvents that are insoluble in water and inert to the reaction system used in the present invention include ethylbenzene, n-propylbenzene, iso-propylbenzene, n-butylbenzene, iso-butylbenzene, n-amylbenzene, and n-propylbenzene. -Aromatic hydrocarbons such as hexylbenzene, xylene, ethyltoluene, and trimethylbenzene. The amount of these solvents to be used should be 1 part by weight or more based on the γ-methyl-γ-lactone from the viewpoint of reaction yield. Preferably, it is 1 to 50 parts by weight. If too large a quantity is used, no improvement in the reaction yield will be observed, and the solvent will be recovered by distillation after the reaction, which will be uneconomical, which is not preferable. The reaction of the present invention is preferably carried out at 130°C or higher. At temperatures lower than 130°C, the reaction rate is slow and productivity is poor. More preferred temperature is 150-230
It is ℃. At temperatures higher than 230°C, the reaction rate is fast, but the selectivity of the reaction deteriorates, which is not preferable. In the present invention, there is no difference in yield whether phosphoric acid or condensed phosphoric acid is used alone or in combination as a catalyst. The amount of catalyst used is 1 to 20 per γ-methyl-γ-lactone.
Double molar ratio is preferred. If the amount is less than 1 mole, the reaction rate will be extremely slow, which is not preferable. on the other hand,
Even if more than 20 times the mole is used, no improvement in reaction yield is observed, and furthermore, the amount of solvent added during dehydration treatment in the recovery step described later increases, which is uneconomical. The dehydrated condensate solution after the reaction of the present invention is treated as follows. 0.5 to the catalyst contained in the dehydration condensation liquid
~5 parts by weight of water is added to separate the organic and aqueous layers, from which the raw materials and products are recovered by distillation. On the other hand, for example, γ-methyl-γ-valerolactone and its dehydrated product 3-methyl-2-
Substances with a small number of carbon atoms, such as cyclopentenone, are easily soluble in water and are present in large quantities in the aqueous layer. It will be collected. Organic solutions that do not dissolve in water used here include chloroform, dichloromethane, dichloroethane,
Ether etc. are used. For example, γ-methyl-
γ-decalactone and its dehydrated product 2-
Products with a large number of carbon atoms, such as pentyl-3-methyl-2-cyclopentenone, are difficult to dissolve in water, so extraction with the solvent used in the reaction is not a problem. This extract, together with the organic layer, is sent to a recovery step in order to recover the contained raw materials and products by distillation. It is of course possible to recover the catalyst contained in the aqueous layer after the raw materials and products have been extracted and removed by simply evaporating the aqueous layer. However, it is preferable to collect it in the following manner. By adding 0.5 to 5 parts by weight of the solvent used in the reaction based on the amount of catalyst contained and heating to near the boiling point of the solvent, water is removed and recovered together with the solvent. Next, the present invention will be explained in more detail with reference to specific examples, but the present invention is not limited thereto.
Each component was measured by gas chromatography analysis. Example 1 A thermometer, a stirring device,
A condenser was installed. 450 g of 85% phosphoric acid and 900 g of mesitylene were placed in a four-necked flask and heated until the mesitylene refluxed, and then the water that had refluxed together with the mesitylene was distilled off together with a small amount of mesitylene. The total amount of mesitylene and water distilled off is
It weighed 825g. Next, put 90g of γ-methyl-γ-valerolactone into a four-necked flask and bring the internal temperature to 165.
℃ and stirred for 1 hour while the water produced was distilled off along with a small amount of mesitylene. Immediately after the reaction was completed, the mixture was cooled to room temperature. The total amount of mesitylene and water distilled off was 11 g. Next, 760 g of water was added, stirred, and allowed to stand to separate into an organic layer and an aqueous layer. Then add 150ml of chloroform to the aqueous layer,
Dissolved raw materials and products were extracted. The same operation was performed three times. Next, mesitylene was distilled off from the organic layer, and chloroform was distilled off from the chloroform layer. The respective residual liquids were combined and distilled under reduced pressure to obtain 3-methyl-2-cyclopentenone and γ-methyl-γ-valero. 16.4 lactones each
g and 96.4 g were obtained. The conversion rate of γ-methyl-γ-valerolactone was 22.9%, and the conversion rate of 3-methyl-2-
The selectivity for cyclopentenone was 94.3%. Example 2 After extracting and removing the raw materials and products of Example 1, the aqueous layer and 300 g of mesitylene were placed in a four-necked flask and heated until the mesitylene refluxed, and then the water that had refluxed together with the mesitylene was distilled off together with the mesitylene. The catalyst was recovered. The total amount of catalyst and mesitylene remaining in the four-necked flask was 531 g. Next, 750g of mesitylene and γ-methyl
90 g of γ-valerolactone was added and the same experiment as in Example 1 was conducted to obtain a conversion rate of γ-methyl-γ-valerolactone of 21.1% and a selectivity of 3-methyl-2-cyclopentenone of 95.5%. Example 3 Same procedure as Example 1 except that γ-methyl-γ-decalactone was used instead of γ-methyl-γ-valerolactone in Example 1, and mesitylene was used instead of chloroform as the extraction agent. The experiment was conducted and 32.9 g and 31.2 g of 2-pentyl-3-methyl-2-cyclopentenone and γ-methyl-γ-decalactone were obtained, respectively. γ-methyl-γ
-The conversion rate of decalactone was 65.3%, and the selectivity of 2-pentyl-3-methyl-2-cyclopentenone was 62.0%. Example 4 450 g of 85% phosphoric acid and 900 g of xylene were placed in a four-necked flask (No. 3) and heated until the xylene refluxed, and then the water that had refluxed with the xylene was distilled off together with a small amount of xylene. The total amount of xylene and water distilled off was 79.2 g. Next, 90 g of γ-methyl-γ-valerolactone was placed in a four-necked flask, the internal temperature was raised to 140°C, and the mixture was stirred for 5 hours while the produced water was distilled off along with a small amount of xylene.
Immediately after the reaction was completed, the mixture was cooled to room temperature. The total amount of xylene and water distilled off was 13.1 g. Next, 760 g of water was added, stirred, and allowed to stand to separate into an organic layer and an aqueous layer. Then, 150 ml of chloroform was added to the aqueous layer to extract dissolved raw materials and products. The same operation was performed three times. Next, xylene was distilled off from the organic layer, chloroform was distilled off from the chloroform layer, and the respective residual liquids were combined and distilled under reduced pressure to obtain 3-methyl-2-cyclopentenone and γ-methyl-γ-valero. 13.5 g and 69.5 g of lactone were obtained, respectively. The conversion rate of γ-methyl-γ-valerolactone was 22.8%,
The selectivity of 3-methyl-2-cyclopentenone is
It was 78.0%. Example 5 The aqueous layer after extracting and removing the raw materials and products of Example 4 and 300 g of xylene were placed in a four-necked flask (No. 3), heated until the xylene refluxed, and then the water that had refluxed together with the xylene was refluxed together with the xylene. The catalyst was recovered by distillation. The total amount of catalyst and xylene remaining in the four-necked flask was 542.5 g. Next, 40 g of xylene and 90 g of γ-methyl-γ-valerolactone were added and the same experiment as in Example 4 was carried out, and the conversion rate of γ-methyl-γ-valerolactone was 20.9% and 3-methyl-2-cyclopentenone. The selection rate was 75.1%. Example 6 Same as Example 4 except that γ-methyl-γ-decalactone was used instead of γ-methyl-γ-valerolactone, the stirring time was 3 hours, and xylene was used instead of chloroform as the extraction agent. An experiment similar to Example 4 was carried out and 2-pentyl-3-methyl-2-cyclopentenone and γ-methyl-γ-
48.9 g and ^43-7 g of decalactone were obtained, respectively.
The conversion rate of γ-methyl-γ-decalactone is 51.5
%, and the selectivity of 2-pentyl-3-methyl-2-cyclopentenone was 60.3%. Example 7 200g of orthophosphoric acid and 1000g of mesitylene in 3/4
The mixture was placed in a neck flask, the internal temperature was brought to 165°C, and 50 g of γ-methyl-γ-valerolactone was added. 1 while distilling off the produced water along with a small amount of mesitylene.
Stir for hours. Immediately after the reaction was completed, the mixture was cooled to room temperature. The total amount of mesitylene and water distilled off was 4.3
It was hot at g. Next, 400 g of water was added, stirred, and allowed to stand to separate into an organic layer and an aqueous layer. Then, 50 ml of chloroform was added to the aqueous layer to extract dissolved raw materials and products. The same operation was performed three times. Next, mesitylene was distilled off from the organic layer, and chloroform was distilled off from the chloroform layer. The respective residual liquids were combined and distilled under reduced pressure to obtain 3-methyl-2-cyclopenteno and γ-methyl-γ.
- Obtained 7.2g and 41g of valerolactone, respectively. The conversion rate of γ-methyl-γ-valerolactone is
The selectivity for 3-methyl-2-cyclopentenone was 95.1%. Example 8 142 g of phosphorus pentoxide and 48.6 g of water were placed in a four-necked flask (No. 3) and stirred to convert condensed phosphoric acid into XH ₂ O.
A condensed phosphoric acid in which X/y=R when expressed as yP ₂ O ₅ was 2.7 was obtained. Next, add 1000g of mesitylene,
The internal temperature was raised to 165°C, 50 g of γ-methyl-γ-valerolactone was added, and the mixture was stirred for 1 hour while the produced water was distilled off along with a small amount of mesitylene. Recovery of raw materials and products followed Example 7. 3-Methyl-2-cyclopentenone and γ-methyl-γ-
10.8g and 36.2g of valerolactone were obtained, respectively. The conversion rate of γ-methyl-γ-valerolactone is
The selectivity for 3-methyl-2-cyclopentenone was 93.3%. Example 9 150 g of orthophosphoric acid and 50 g of condensed phosphoric acid (R=2.7) were placed in a four-necked flask (No. 3) and stirred. Next, 1000 g of mesitylene was added, the internal temperature was raised to 165°C, 50 g of γ-methyl-γ-valerolactone was added, and the mixture was stirred for 1 hour while distilling off the produced water along with a small amount of mesitylene. Recovery of raw materials and products is as in Example 7.
I followed. 3-methyl-2-cyclopentenone and γ-methyl-γ-valerolactone, respectively.
8.0g and 39.8g were obtained. The conversion rate of γ-methyl-γ-valerolactone was 20.4%, and the conversion rate of 3-methyl-γ-valerolactone was 20.4%.
The selectivity for 2-cyclopentenone was 94.1%.

Claims (1)

[Claims] 1 γ-Methyl-γ- represented by the general formula [Formula] (R represents hydrogen or an alkyl group)
When producing 3-methyl-2-cyclopentenones represented by the general formula [formula] by dehydration condensation of lactones, the dehydration condensation is carried out in a solvent that does not dissolve in water and is inert to the reaction system. 3-methyl-2-cyclopene, characterized in that phosphoric acid and/or condensed phosphoric acid is added as a catalyst, and water generated by the reaction is removed from the system together with the solvent while heating near the boiling point of the solvent. Method 2 for producing tenones Method 3 according to claim 1, wherein R of γ-methyl-γ-lactones is an alkyl group and has 1 to 5 carbon atoms Process 3 of γ-methyl-γ-lactones Method 4 according to claim 1, in which R is hydrogen; Method 5 according to claim 1, in which the solvent is an aromatic hydrocarbon; γ-methyl-γ-lactones 1, where the solvent is Method 6 according to claim 1 or 4, wherein the catalyst is used in an amount of 1 part by weight or more and 50 parts by weight or less. The method according to claim 1, wherein the catalyst is phosphoric acid. 7. The method according to claim 6, wherein the phosphoric acid is recovered from the aqueous layer after adding water to the dehydration condensation liquid and separating it into two layers, an organic layer and an aqueous layer. Method 9 according to claim 7, which is carried out by adding a solvent to the aqueous layer, heating it, and dehydrating it together with the solvent. Phosphoric acid and/or condensed phosphoric acid is a γ-methyl-γ-lactone. Method 10 according to claim 1 or 6, which is used in an amount of 1 to 20 times the molar amount, Method 11 according to claim 1, wherein the heating temperature is 130° C. or higher is 150°C or more and 230°C or less, the method according to claim 10