JPH0353292B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a carboxylic acid ester by reacting a carboxylic acid amide, an alcohol, and carbon monoxide. Carboxylic acid esters are industrially important substances, and examples of producing carboxylic acid esters from carboxylic acid amides include methyl acetate from acetamide,
Examples include the production of acrylic ester from acrylamide, methacrylic ester from methacrylamide, and α-hydroxyisobutyric ester from α-hydroxyisobutyric acid imide, all of which are industrially useful processes. Conventionally, as a method for producing a carboxylic acid ester from a carboxylic acid amide, a method of decomposing the carboxylic acid amide using water and methanol in the presence of sulfuric acid is known. However, this method has various drawbacks, such as the production of a large amount of ammonium sulfate as a by-product, and the need to use expensive corrosion-resistant materials because of the use of sulfuric acid. In order to overcome these drawbacks, a method is known in which a carboxylic acid amide is reacted with an alcohol to produce a carboxylic acid ester without using sulfuric acid. For example, JP-A-52-3015 describes a method in which a carboxylic acid amide and a primary alcohol are reacted in the presence of an at least partially dissolved metal carboxylate in which the anion is the residue of an acid forming an ester. In 141216/1987, at least one member selected from the group consisting of copper, nickel, cobalt, and their compounds, and at least one of a phenol group, an aldehyde group, a ketone group, a carboxylic acid group, an amide group, and a basic nitrogen-containing group. A method is described in which methacrylamide and a primary alcohol are reacted in the presence of a catalyst comprising a combination of at least one compound selected from the group consisting of one compound. Furthermore, in JP-A-53-144524, the reaction is carried out using at least one member selected from the group consisting of lead, cadmium, titanium, tin bromide, fluoride, iodide, nitrate, phosphate, and borate. The method is described. However, in all of these methods, the activity is low, or the generated carboxylic ester and ammonia easily react and change into carboxylic acid amide and alcohol again, so the generated ammonia must be used intermittently or continuously. It requires operations such as carrying out the reaction while removing it from the reaction system, and is not necessarily an advantageous method from an industrial perspective. The present invention is a method for producing a carboxylic acid ester without generating ammonia, and is a method for producing a carboxylic acid ester by reacting a carboxylic acid amide, alcohol, and carbon monoxide, and producing formamide as a by-product. Formamide can be used as a solvent, etc., and can also be converted into hydrocyanic acid by dehydration or deetherification, so it can be recycled and used as a raw material for carboxylic acid amide. The carboxylic acid amide used in the present invention can be a commonly known amide obtained by hydration of nitrile, reaction of amine with carbon monoxide, or other methods, and has the general formula (Here, R ₁ , R ₂ , and R ₃ are hydrogen, a hydroxyl group, or a C ₁ to C ₅ alkyl group or alkenyl group, and may be the same or different. Also, R ₄ , _R5 is hydrogen or a _C1 - _C5 alkyl group). Examples of the carboxylic acid amide represented by this formula include acetamide, lactic acid amide, acrylamide, methacrylamide, α-hydroxyisobutyric acid amide, and the like. Furthermore, examples of the alcohol used in the present invention include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, and octyl alcohol. In addition, when performing the reaction of alcohol, carbon monoxide, and carboxylic acid amide in the presence of a formic acid ester, the reaction can be carried out without any problems by making the alcohol correspond to the alkyl group of the formic acid amide. Further, the molar ratio of carboxylic acid amide and alcohol used in the present invention is 1:1 to 30, preferably 1:3 to 1:20. The partial pressure of carbon monoxide is 10 to 500 Kg/cm ² , preferably 30 to 400 Kg/cm ²
It is. Note that these conditions are not particularly limited to the above numerical values, and may be appropriately selected in consideration of the type of amide, reaction conditions, etc. The catalyst used in the present invention is an amidine or a tertiary amine, and by using an amidine or a tertiary amine in combination with a metal carbonyl, a more favorable effect can be obtained than when using an amidine or a tertiary amine alone. . Specifically, the amidine includes 1,3-diazabicyclo-[5,4,0]-undecene (DBU), 1,5-diazabicyclo-[4,3,
0]-Nonene (DBN), and the tertiary amines include N-methylpyrrolidine, N-ethylpyrrolidine, 4,4'-trimethylenebis(N-methylpiperidine), N-methylpyrrolidine, N-ethyl Pyrrolidine, dipiperidinomethane, dipiperidinoethane, dipiperidinopropane, N,N'-dimethylpiperazine, N,N'-diethylpiperazine,
Trimethylamine, triethylamine, tripropylamine, tributylamine, tetramethylethylenediamine, tetramethyltetramethylenediamine, dimethylethylamine, triethylenediamine, N,N-dimethylcyclohexylamine, and the like are used. In addition, metal carbonyls include chromium carbonyl Cr(CO) ₆ and molybdenum carbonyl Mo
(CO) ₆ , tungsten carbonyl W (CO) ₆ , manganese carbonyl Mn ₂ (CO) ₁₀ , rhenium carbonyl Re ₂ (CO) ₁₀ , iron carbonyl Fe (CO) ₅ , Fe ₂
(CO) ₉ , Fe ₃ (CO) ₁₂ , Ruthenium carbonyl Ru ₃
(CO) ₁₂ , Osmium carbonyl Os ₃ (CO) ₁₂ , Cobalt carbonyl CO ₂ (CO) ₈ , Rhodium carbonyl
Rh ₄ (CO) ₁₂ , Iridium carbonyl Ir ₄ (CO) ₁₂ ,
Nickel carbonyl Ni(CO) ₄ etc. are used. In addition, in the present invention, in place of the metal carbonyl, oxides, hydroxides, sulfates, nitrates, carbonates, formates, acetates, and hydroxides of the corresponding metals capable of forming the metal carbonyl under the reaction conditions are used. It is also possible to use acid salts, naphthenates, acetylacetone salts, chelate compounds of polyaminocarboxylic acid salts, halides, and the like. The amount of catalyst used in the present invention is in the range of 0.001 to 1 mole per mole of carboxylic acid amide when using amidine or tertiary amine.
It is not economically advisable to add more than necessary, and if the amount added is too small, a sufficient reaction rate cannot be obtained, so the preferable amount is 0.003 to 0.5 mol. Further, the amount of metal carbonyl to be used can be selected in the range of 0.0001 to 0.5 mol, preferably in the range of 0.001 to 0.2 mol, per 1 mol of carboxylic acid amide. The reaction temperature in the present invention is 50 to 400°C, preferably 100 to 300°C. If the reaction temperature is lower than 50°C, the reaction rate is slow and sufficient reaction results cannot be obtained, and if the reaction temperature is higher than 400°C, side reactions such as decomposition and polymerization of carboxylic acid amides, carboxylic acid esters, and formamide may occur. Should be avoided due to triggering. The present invention can be carried out using any of the batch, semi-batch and flow methods. In the present invention, without using ester as a raw material, carboxylic acid amide and alcohol,
Carboxylic acid esters can be obtained with high selectivity by reacting with carbon monoxide. In addition, in the present invention, ammonia is not produced as a by-product, and formamide, which is useful as a solvent or as a raw material for producing hydrocyanic acid, is simultaneously produced, so it has extremely great industrial significance. Example 1 70ml of α-hydroxyisobutyric acid amide was placed in a stainless steel autoclave with an internal volume of 100ml.
mol, methanol 560 mmol, DBU3.0 as catalyst
mmol, the inside of the autoclave is replaced with carbon monoxide gas, and the autoclave is further pressurized with carbon monoxide gas, followed by heating and shaking. The temperature inside the autoclave is
When the temperature reaches 180℃, the reaction is continued for 180 minutes while supplementing carbon monoxide gas so that the reaction pressure becomes 150Kg/cm ² . After cooling, the autoclave was returned to normal pressure, and the reaction product was taken out and analyzed by gas chromatography. The conversion rate of α-hydroxyisobutyric acid amide is 45.0
% and the yield of methyl α-hydroxyisobutyrate is
The rate was 44.4%, and the selection rate was 98.6%. Also,
The yield of formamide at this time was 40.8%, and the selectivity was 90.8%. Examples 2 to 15 Table 1 shows the results of reactions conducted using the same autoclave and the same experimental method as in Example 1.

【table】

【table】

[Table] Example 16 The same autoclave as in Example 1 was used, and a reaction was carried out in the same manner as in Example 1, except that 70 mmol of lactic acid amide, 560 mmol of methanol, and 3.0 mmol of DBU as a catalyst were charged. As a result, the conversion rate of lactic acid amide was 55.5%, the yield of methyl lactate was 45.5%, and the selectivity was 82.0%.
It was hot. The yield of formamide at this time was 45.0%
The selection rate was 81.1%. Example 17 Using the same autoclave as in Example 1, methacrylamide 70 mmol and methanol 560 m
The reaction was carried out in the same manner as in Example 1, except that 3.0 mmol of DBU was charged as a catalyst. As a result, the conversion rate of methacrylamide was 39.5
% and the yield of methyl methacrylate is 34.6
%, the selectivity was 87.6%, the yield of formamide at this time was 35.1%, and the selectivity was 88.9%.

Claims (1)

[Claims] 1. Method for producing carboxylic acid ester, characterized by reacting carboxylic acid amide, alcohol, and carbon monoxide