JPS6293257A - Production of 3-2-oxocyclohexyl propionic acid ester - Google Patents

Abstract

PURPOSE:To obtain the titled compound in high conversion and yield, by reactying a cyclohexanone having active hydrogen atom at the alpha-position with an acrylic acid ester in the liquid phase in the presence of a specific amount of pyrrolidine. CONSTITUTION:A cyclohexanone having active hydrogen atom at the alpha-position is reacted with an acrylic acid ester in the liquid phase in the presence of 0.02-0.2mol, based on 1mol acrylic acid ester, pyrrolidine at 120-200 deg.C to afford the aimed compound. The use of excess cyclohexanone suppresses side reaction and 1.2-8mol, based on 1mol acrylic acid ester, cyclohexanone is preferably used. USE:An intermediate raw material for dihydrocoumarin or coumarin, etc., useful in perfume industry.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing 8-(2-oxocyclohexyl)propionic esters by reacting cyclohexanones and acrylic esters.

a-(2-oxocyclohexyl)propionic acid esters are useful as intermediate raw materials, etc., and can be converted into dihydrocoumarin or coumarin useful in the fragrance industry, for example, by the method described in U.S. Pat. No. 8,442,910. <Prior art> Cyclohexanone having an active hydrogen atom at the α-position can be
When producing 8-(2-oxocyclohexyl)propionic ester by adding acrylic ester, which is an ester of β-unsaturated carboxylic acid, pyrrolidine enamine obtained by the reaction of pyrrolidine and cyclohexanone is used as MK. What is sulco? , Journal of A
me-rican Chemical 5ociety
, Vol. 85.196B.

It is described in P2O7-222 and is well known.

JP-A-55-28988 also discloses the use of an adduct of pyrrolidine and acrylic ester as a catalyst.

<Problem that the invention attempts to solve> However, using the former pyrrolidine enamine, 8-
When producing (2-oxocyclohexyl)propionic acid ester, it is necessary to use at least an equimolar amount of pyrrolidine to cyclohexanone, and furthermore, it is complicated to synthesize pyrrolidine enamine in advance.

On the other hand, when using the latter adduct of pyrrolidine and acrylic ester as a catalyst, it is necessary to preliminarily synthesize the adduct and the conversion rate of acrylic ester is 20 to 20%.
It has drawbacks such as the need for 90% pongee retention.

Means for Solving Problems〉 The present invention involves reacting cycloJ hexanones having an active hydrogen atom at the d-position in an acrylic acid ester liquid phase.
．． - In the production of (2-oxocyclohexyl)propionic acid esters, 0.0 per mole of acrylconister to be converted at temperatures between 120 and 200°C.
The present invention relates to a method for producing 8-(2-oxocyclohexyl)propionic acid esters, characterized in that 2 to 0.2 moles of pyrrolidine are present.

Examples of the cyclohexanones having an active hydrogen atom at the α-position used in the present invention include cyclohexanone, 2-alkylcyclohexanone, 4-alkylcyclohexanone, and other cyclohexanone derivatives.

Examples of acrylic esters include esters of acrylic acid and aliphatic alcohols, ring alcohols, and aromatic alcohols, and among these, methyl esters and ethyl esters are preferred.

The molar ratio of cyclohexanones to acrylic ester is
Theoretically, the ratio is 1:1, but side reactions can be suppressed by using an excess of cyclohexanones. Although the optimum molar ratio of cyclohexanone to acrylic ester can be easily determined by experiment, it is preferred to use 1.2 to 8 moles of cyclohexanone per mole of acrylic ester.

Further, in order to prevent polymerization of the acrylic ester during the reaction, a polymerization inhibitor such as hydroquinone may be added.

It is not necessary to prepare and add pyrrolidine in advance as an adduct with cyclohex. The amount of pyrrolidine is preferably between 0.02 and 0.2 mole per mole of acrylic ester to be converted. Below this range, the reaction rate is slow and it takes a long time to complete the reaction. Moreover, beyond this, 3-(2-
The yield of oxocyclohexyl)propionic acid esters decreases.

The process according to the invention is carried out at temperatures between 100 and 220°C. For example, when the temperature exceeds 220°C, the reaction yield decreases, and conversely, when the temperature falls below 100°C, the reaction rate becomes extremely slow. A particularly preferred temperature is 120 to 200°C.

The reaction pressure is not critical and may be adjusted so that the reaction occurs in the liquid phase. As a solvent, well-known hydrocarbons can also be used, but if cyclohexanones are used in excess of the acrylic ester, there is no need to use them. Any effective container may be used, and examples include a mixing tank equipped with a simple stirrer blade or a tank equipped with an external circulation pump. It may be continued in succession or in batches.

In the method of the present invention, it is possible to convert all or part of the acrylic ester, but it is preferable to convert 90% or more of the acrylic ester. This is because the circulating amount of unreacted acrylic ester, which is relatively highly polymerizable, can be reduced.

After the reaction is completed, the reaction solution can be separated, for example, by distillation, and the unreacted acrylic ester and cyclohexanones can be reused.

<Examples> The method of the present invention will now be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A glass autoclave with an internal volume of 1 t was charged with 867.5 f cyclohexanone, 215 f methyl acrylate, and 8.8 f pyrrolidine and stirred for 1 L.
The mixture was heated to 150° C. and then reacted for 5 hours. The reaction solution was then rapidly cooled and analyzed by gas chromatography, which revealed that it contained 124.9y of cyclohexanone, 4.81 of methyl acrylate, and 482.4f of methyl 8-(2-oxocyclohexyl)propionate. .

The conversion rates of cyclohexanone and methyl acrylate were 66% and 98%, respectively, and the yield was 94% based on the charged methyl acrylate.

Example 2.3 The same procedure as in Example 1 was carried out except that the temperature was changed. The results are shown in Table 1 below.

Table 1 Comparative Example 1.2 The same procedure as in Example 1 was carried out except that the reaction temperature was changed. The results are shown in Table 2 below.

Table 2 Example 4.5 The same procedure as in Example 1 was carried out except that the amount of pyrrolidine used as a catalyst was changed. The results are shown in Table 8 below.

Table 8 Comparative Example 3.4 The same procedure as in Example 1 was carried out except that the amount of pyrrolidine used as a catalyst was changed. The results are shown in Figure 4 below.

Table 4 Example 6 Contents 867.51 cyclohexanone, 2501 ethyl acrylate, and 8.8 g of pyrrolidine were charged into a glass autoclave with contents@It, and the mixture was heated to 150° C. under autogenous pressure while stirring, and then reacted for 6 hours. Ta. Next, the reaction solution was rapidly cooled and analyzed by gas chromatography, and it was found that 122.5N cyclohexanone, 2.6
f of ethyl acrylate and 468.81 of 8-(2-
It contained ethyl oxocyclohexyl)propionate.

The conversion rates of cyclohexanone and ethyl acrylate were 66.7% and 99%, respectively, and the yield was 98.6% based on the charged ethyl acrylate.

<Effects of the Invention> According to the present invention, the reaction in column 2 can be performed without performing the two-step reaction of reacting either cyclohexanones or acrylic acid ester with pyrrolidine and then reacting with scolding. pyrrolidine and pyrrolidine can be reacted simultaneously in one step, with a high conversion rate,
yield can be obtained.

Claims (1)

[Claims] Acrylic acid to be converted at a temperature of 120 to 200°C when producing 3-(2-oxocyclohexyl)propionic esters by reacting cyclohexanones having an active hydrogen atom at the α-position with acrylic esters in a liquid phase. A method for producing 3-(2-oxocyclohexyl)propionic acid esters, characterized in that 0.02 to 0.2 mol of pyrrolidine is present per 1 mol of ester.