DE1593320C - Process for the preparation of carboxamides - Google Patents

Description

1 2

The invention relates to a method for production. According to a further preferred embodiment

of carboxamides by hydration of car- form of the process of the invention is the nitrile

boron nitriles in the presence of catalysts. dissolved in a liquid organic solvent,

Process for converting nitriles to amides whose boiling points are working at elevated tems known in the art. In general, 5 ■ temperature is allowed. Thereby the solution of the nitrile heated to a catalyzed by acid or alkali, preferably to reflux temperature, sierle hydrolysis under carefully regulated conditions. In order to keep the formation of acid to a minimum, use a suitable solvent measure limit. Most of these methods are dissolved nitrile with a sufficient amount of hydra the conversion of nitriles generally non-ionized manganese dioxide, the one molar equivalent of what is applicable. A widespread method is derived from containing water, heated for a suitable time to the von Radzisewskik, Ber. 17 (1884). 1289 to effect conversion of the nitrile into the amide. 1290, in which, using an alkali, the minimum temperature to which the reaction catalyst hydrogen peroxide is heated as a reactant mixture is not particularly used will. Although this synthesis is relatively 15 dend. as long as practically effective over the surrounding star it is dangerous and therefore not peralur lying temperatures are used, fully satisfactory. To get practical reaction rates too

In conventional manufacturing processes, temperatures are above about 50C

z. B. Acrylamide from acrylonitrile is sulfuric acid used. Very high temperatures, such as B. 400'C.

monohydrate used. The resulting acrylamide ⁵ 20 must be avoided in order to avoid the possibility of it entering

Sulphate is an anhydrous "salt", which should then be avoided under reverse reactions. Also the

Use of various alkaline materials. The time required for implementation varies widely

like ammonia, is neutralized. If in the first limits and depends on the ease. with the

Step too little water is available. is the hy- the nitrile is converted into the amide. In general

dratization is incomplete, and the sales are 25 mine, the implementation time is several hours

low. When there is too much water. occurs as the.

second reaction has another hydrolysis to form the amide synthesis of the present invention

of acrylic acid, which, in turn, has a wide range of applications and is generally used for

yields of amide can be reduced. It is therefore not possible to generate amides from nitriles. So

manoeuvrable, the amount of water available to 30, the ^ Nilril the general formula R —-C == N

regulate, as well as have the ratio of water to nitrile, in which R is a hydrocarbon free. So

and / or amide control. The usual one can be R z. B. an alkyl, cycloalkyl, alkenyl. Cyclo-

Neutralization with, for example, sodium hydroxide, alkynyl, aryl, alkary, alkyl or heterocyclic

not satisfactory, since again water can be one of the reac radicals, which may have additional substituents.

tion product, so that further hydrolysis occurs, 35 such as halogen atoms, alkoxy, nitro, ester, ketone

which can lead to the formation of acid. or can contain acid groups. Polynitriles can

In addition, because of the reactions shown, must also be according to the inventive method

the other reaction parameters. drive to be converted.

such as temperature, reaction time, concentration and It is known that certain nitriles are more difficult

Mixing ratios are carefully regulated, 40 are converted into amides than others, namely

to avoid this further hydrolysis. due to certain factors, such as steric hindrance

The invention was based on the object of a change by substituents on the nitrile. General

new process for converting nitriles into is that aryl and heterocyclic nitriles are more easily converted into

Finding amides, the broad applicability amides are convertible as alkyl nitriles or vinyl

owns, safe to handle and convenient 45 nitrile. When it comes to nitriles that are difficult to

is to be carried out. riger to convert, you will feel the usual

The invention use a method of chemical aids and the reaction preparation of carboxamides by hydrazine conditions vary so that the synthesis of carboxylic acid in the presence of optitation _ma le "provides results. Such modifications umKatalysatoren, which is characterized, take 50 E.g. the use of higher temperatures so that the carboxylic acid nitrile in the presence of longer reaction times, other solvents water and manganese dioxide or hydrated manganese dioxide or larger quantities of manganese dioxide Reakamidbildung sufficient time to a heated above üonsbedingungen of illustration only and are intended to about 50 ⁰ C lying temperature and the preservation 55 understood that the invention do not limit, tene carboxamide in a known manner to a preferred embodiment of the reaction Erfinvon separating products. Many solvents can be used.

In the process according to the invention none of the nitrile to be converted was dissolved and their boiling point was further Hydrolysis with formation of acid, such as dot. as stated earlier, the application increased Acrylic acid, observed; a large 60 temperatures are therefore allowed. Suitable solvents are Range of variation with regard to the reaction conditions, inter alia, dioxane, chloroform, benzene. Toluene, possible without drastic effects on the pyridine. / i-picoline or tert-amyl alcohol. Even though Reaction outcome would be expected. it is not necessary in the case of the according to the invention

A preferred embodiment of the invention to apply a solvent synthesis. ~ Used

is characterized in that 65 _m as a catalyst, but preferably one, because solution

Uses manganese dioxide; which practically neutral means facilitate the implementation of the reaction

is, d. H. in the case of a slurry of 1 g in 10 g insofar as they are used to control the temperature and

Water shows a pH of 6.0 to 8.0. serve as a diluent in the filtration.

IO

Anhydrous manganese dioxide can be used as a catalyst, it being necessary that water is present in the reaction mixture. Molar equivalents of water are required for the reaction. However, it is best to use hydrated or activated manganese dioxide to provide the required water to deliver. The amount of catalyst to be used depends on various factors such as the reaction temperature and the desired conversion speed. In general, (on the Nitrile based) about 0.1 to about 5 molar equivalents of catalyst is used.

The following examples illustrate the synthesis according to the present invention in detail. In these examples, the activated manganese dioxide was prepared from the reaction of equivalent amounts of manganese sulfate with potassium permanganate in the presence of a small excess of sodium hydroxide, the temperature being kept at 80 ° C. The manganese dioxide produced was filtered off and washed with distilled water until the wash waters were neutral. Since the manganese dioxide catalyst should preferably be practically neutral, it should therefore be washed with acid, if necessary, in order to neutralize it. A “practically neutral” manganese dioxide catalyst is understood to be one which has a pH of about 6.0 to 8.0 when 1.0 g of catalyst is suspended in 10 g of water. The product was exposed in an oven at 100 to 110 ⁰ C to constant weight and then dried to atmospheric moisture until its weight did not increase more. The manganese dioxide produced in this way contained about 13.5% water, corresponding to the approximate molecular formula MnO ₂ · 1 / 2H ₂ O.

example 1

A solution of 1.56 g of acetonitrile was stirred with 10.0 g of the manganese dioxide prepared above heated under reflux in 100 ecm of dioxane for 5 hours. After filtering and evaporating the 1.90 g (84%) of acetamide were obtained from the solvent, melting point 68 to 72 ° C.

Example 2

A mixture of 4.125 g of benzonitrile and 5.0 g of the above prepared manganese dioxide was added with stirring Heated under reflux in 100 ecm benzene for 5 hours. After filtering and removing the solvent 2.522 g of moist, yellowish crystals were isolated. The infrared spectrum indicated that the product Was benzamide containing some unreacted benzonitrile.

35

40

45 The reaction was carried out using 4.96 grams of benzonitrile and 10.0 grams of the above Manganese dioxide and 100 ecm benzene repeated for 5 hours. The yield of benzamide, the only one Containing trace nitrile was 3.74 g (65%). Mp. 126 to 128 ° C.

Example 3

A solution of 4.96 g of benzonitrile in 100 ecm of dioxane was mixed with 10.0 g of the manganese dioxide prepared above Heated under reflux with stirring for 5 hours. Filter and evaporate the solvent gave 5.35 g (92%) of benzamide crystals, melting point 125 to 128 ° C. The infrared spectrum showed that the product contained little or no unreacted benzonitrile.

Example 4

A suspension of 10 g of the above prepared Manganese dioxide in 100 ecm of dioxane, which contained 1.59 g of acrylonitrile, was stirred for 5 hours on Heated to reflux. Filtration and evaporation of the solvent gave 0.777 g (37%) of white crystals of acrylamide; Melting point 54 to 56 ° C.

Example 5

A similar reaction using 1.59 grams of acrylonitrile, 10.0 grams of the manganese dioxide prepared above and 100 ecm of dioxane gave after 16 hours 1.282 g (60%) of acrylamide, melting point 43 bis 66 ° C. After recrystallization from benzene-hexane the melting point rose to 72 to 73 ° C.

Examples 6 to 51

In the following examples, a solution of a conventional amount (usually 0.03 to 0.07 mol) of a nitrile in 100 ecm of dioxane with a slight excess (10 to 20 g) of hydrating manganese dioxide (MnO ₂ · 1 /? H ₂ O) 6 hours with stirring ~ heated under reflux. Unless otherwise stated, the solid was filtered off and the crude product was isolated by evaporation of the solvent under reduced pressure. In all cases the identity of the amide and the presence of any unreacted nitrile were determined by means of the infrared spectrum of the crude product. The amide was recrystallized from a suitable solvent and its melting point was determined. In some cases, deviations were made from the above procedure with regard to the use of anhydrous manganese dioxide or the type of work-up of the product. These deviations are noted in the following table, in which the results are compiled.

Table I.
The hydration of nitriles to amides using manganese dioxide

example Nitrile Propionitrile Quantity ■ nitrile crowd MnO ₂ *) yield
of amide % Melting point, C. literature n-butyronitrile G Mole G Mole G 61 observed 79 6th Isobutyronitrile 3,915 0.071 20th 0.208 3.182 60 73-74 115 7th n-valeronitrile 5,000 0.072 20th 0.208 3.754 56 115-117 128 8th n-capronitrile 5,000 0.072 20th 0.208 3.531 57 127-129 114-116 9 5,000 0.060 20th 0.208 3.483 40 105-107 101 10 5,000 0.052 10 0.104 2,379 100-101

*) Calculated as MnO ₂ · '/, H ₂ O: anhydrous material plus added water was only used for a).

5 continuation Mole crowd MnO ₂ *) 6th % Melting point, ⁰ C literature example Nitrile Amount of nitrile 0.005 G Mole yield
of amide 80 observed 98.5 G 0.043 10 0.104 G 5 98-99 140 11th n-tridecanonitrile 0.966 0.043 10 0.104 0.847 91 143 97 12th o-tolunitrile 5,000 0.043 10 0.104 0.310 99 91-92 160 13th m-tolunitrile 5,000 0.042 10 0.104 5.296 90 160-161 112 14th p-tolunitrile 5,000 0.025 10 0.104 5.718 10 109-111 205 15th 3,4-dimethylbenzonitrile 5.450 0.048 10 0.104 5.603 93 207-208 129-131 16 α-naphthonitrile 3.858 0.048 10 0.104 0.432 90 127-131 155 17th Nicotinonitrile 5,000 0.075 10 0.104 5.440 34 157-158 102-106 18th Isonicotinonitrile 5,000 0.075 20th 0.208 5.247 85 109 125-126 19th Methacrylic acid nitrile 5,000 0.079 20th 0.208 2.154 87 128-129 170 20th Cyclopropanecarbonitrile 5,000 0.063 20th 0.208 5.437 47 168-171 250 21 Malonitrile ¹ ) 5,200 _# 0.053 20th 0.208 6,993 82 236-240 174 22nd Succinonitrile ¹ ) 5,000 * 0.046 20th 0.208 2.280 36 181-184 220 23 Glutaronitrile ¹ ) 5,000 0.041 20th 0.208 5.668 68 229-233 174 24 Adiponitrile ¹ ) 5,000 0.040 20th 0.208 2,379 94 172-174 - 25th Pimelonitrile ¹ ) 5,000 0.039 20th 0.208 5.147 63 > 300 233 26th 1,4-cyclohexanedicarbonitrile ¹ ) 5,400 0.047 20th 0.208 6.413 54 233-235 - 27 Phthalonitriles ³ ) 5,000 0.060 10 0.104 4,139 64 - 170 28 Ethyl cyanoacetate 5.315 0.040 20th 0.208 3,344 83 158-168 158 29 Cyanoacetamide ¹ ) 5,000 0.042 10 0.104 3.739 73 154-158 119 30th Cyanoacetanilide ¹ ) 6,400 0.025 10 0.104 5.944 29 118-120 102 31 α-chloroacetonitrile 3.150 0.024 10 0.104 2.852 14th 71-77 110-111 32 / J-chloropropionitrile 2.276 0.042 10 0.104 0.796 61 76-80 25th 33 / f-bromopropiitrile 3.271 0.041 10 0.104 0.503 81 - 50 34 y-bromobutyronitrile ² ) 6,200 0.042 10 0.104 4.257 82 39 ^ 13 - 35 / J-methoxypropionitrile 3,500 0.051 10 0.104 3.435 66 52-55 40 36 / Msopropoxypropionitrile 4,700 0.040 20th 0.208 4.497 69 - - 37 / f-dimethylaminopropionitrile 5,000 0.071 10 0.104 3.903 32 - 182-184 38 ß-isopropylaminopropionitrile 4,700 0.020 20th 0.208 3.603 97 163-173 - 39 Dimethylcyanamide ¹ ) ■ 5,000 0.0065 20th 0.208 1,978 98 - - 40 Cyanoethyl glycerine ⁴ ) 5,000 0.044 20th 0.208 5,892 8th - 182 41 Cyanoethyl sucrose ⁴ ) 4,978 0.042 20th 0.208 5.797 37 178-182 145 42 Thiodipropionitrile 6,200 0.040 " 20th 0.208 0.612 91 140-144 143 43 Iminodipropionitrile 5,200 0.027 20th 0.208 2,411 93 54 (decomp.) 205 (decomp.) 44 Iminodiacetonitrile ^l ) 3,800 0.020 20th 0.208 4,794 100 201 (decomp.) - 45 Nitrilotriacetonitrile ¹ ) 3,600 0.043 20th 0.208 4,740 (85) 120-132 - 46 Ethylenediamine tetraacetonitrile ¹ ) 4,400 0.052 10 0.104 6.419 - - - 47 Phenylacetonitrile ⁵ ) 5.075 0.035 20th 0.230 4.306 (84) 203-209 - 48 Diphenylacetonitrile ^s ) a) 10,000 0.039 10 0.104 12,440 (74) 190-191 - 49 p-chlorophenylacetonitrile ⁵ ) 5.245 0.040 10 0.115 4.393 (73) - - 50 p-methoxyphenylacetonitrile ⁵ ) a) 5,800 10 0.115 4,314 228 (decomp.) 51 p-nitrophenylacetonitrile ⁵ ) a) 6,500 4.717

*) Calculated as MnO ₂ - '/ ₂ H ₂ O; only in a) was anhydrous material plus added water used.

') The insolubility of carboxylic acid diamides in dioxane made a modification of the general procedure for work-up of the products from the hydration of dinitriles. After filtering the reaction mixture, the manganese dioxide became resuspended in warm water, filtered again and the filtrates evaporated to dryness. The combined weights of the two Fractions (dioxane soluble and water soluble) were taken as the crude yield. This procedure was used for work-up the products made from all dinitriles, from cyanoacetamide, cyanoacetanilide and from several other polyfunctional compounds are used, where the products were insoluble in dioxane.

Another modification of the above procedure was necessary in the case of 1,4-cyclohexanedicarbonitrile, in which the amide is insoluble in both water and dioxane. The manganese dioxide was washed with dimethylformamide as above with water. However, the combined weight of all three fractions was only 712 mg. Therefore the manganese dioxide was dissolved by adding it to 500 ecm 10% sulfuric acid was suspended and a solution of 50 g of sodium metabisulfite in 200 ecm of water was slowly added. The white solid was filtered off, washed thoroughly with water and, after drying in air, gave 5.701 g of the diamide.

² ) The infrared spectrum indicated that the major product obtained from 4-bromobutyronitrile was pyrrolidone (γ-butyrolactam).

³ ) The product was phthalimide.

⁴ ) The reactions were allowed to proceed for 24 hours and worked up according to procedure 1.

⁵ ) Phenylacetonitrile and its derivatives did not easily suffer hydration to the amide, rather a complex mixture of products containing (also the amide) was obtained. Without being bound by any particular theory, these results could be explained on the basis of a side reaction in which coupling between sensitive active methylene groups occurs. There may be competition between the “main” (hydration) reaction and the “side” (coupling) reaction.

As can be seen from the above examples, the conversion of carboxylic acid nitriles into amides generally be accomplished with good yields. However, the examples illustrate furthermore, that in certain cases, depending on the particular nitrile starting material or the solvent in question, the yield of amide will be lower as was desired or special procedures had to be used in order to obtain the product to win. Of course, these examples are only intended for. Explanation of the basics of the present Invention, namely the conversion of nitriles into amides with the help of water and manganese dioxide serve as a catalyst. In special cases, experts will, after knowing the description, “5 knowing without difficulty of taking the various tools disclosed in order to obtain the amide yield increase and / or decrease by-product generation.

One convenient manufacturing method for converting certain nitriles to amides makes use of one azeotropic mixture of nitrile with water. So form z. B. acetonitrile and water a constant Boiling mixture that contains 83.7% nitrile and has a boiling point of 76.5 °. A mixture of equimolar Amounts of acetonitrile and water are refluxed in an apparatus in which the vapors (des azeotropic mixture) envelop a porous container in which there is a certain amount of manganese dioxide is located as a catalyst, and which is attached so that the condensate of the azeotropic mixture strokes through the catalyst bed. Some of the nitrile and water combine under the Influence of the catalyst with the formation of the amide (e.g. acetamide). The unreacted nitrile and the the amide-containing water then passes through the container and is returned to the vessel. The amide is practically non-volatile under these conditions and is concentrated in the Vessel. An effective manufacturing process is thus achieved through continuous circulation. the Experiments have shown that the catalyst does not noticeably decrease in activity on repeated use loses.

Claims (4)

Patent claims: 1. A process for the preparation of carboxylic acid amides by hydration of carboxylic acid in the presence of catalysts, characterized in that heating the carboxylic acid nitrile in the presence of water and manganese dioxide or hydrated manganese dioxide as a catalyst sufficient for the Carbonsäureamidbildung Zeillang to a temperature above about 50 ⁰ C Temperature and separating the carboxamide obtained from the reaction products in a manner known per se. 2. The method according to claim 1, characterized in that the catalyst used is manganese dioxide is used that is practically neutral, d. H. with a slurry of 1 g in 10 g of water exhibits a pH of 6.0 to 8.0. 3. The method according to claim 1 and 2, characterized in that the nitrile in one liquid organic solvent dissolves whose boiling point works at elevated temperature permitted. 4. The method according to claim 1 and 3, characterized in that the solution of the nitrile heated to reflux temperature. 109544/390