CN112028793A - Method for preparing nitrile by bismuth complex catalytic amide dehydration - Google Patents

Abstract

The invention discloses a method for preparing nitrile by catalyzing amide dehydration with a bismuth complex, which comprises the following steps: reacting bismuth salt and a ligand in a solvent at room temperature to obtain a solution containing a bismuth complex; adding amide into the solution containing the bismuth complex, and reacting for 6-18 h at room temperature and normal pressure to realize amide dehydration to generate nitrile, wherein the bismuth complex is used as a catalyst; and separating the obtained reaction liquid to obtain a crude product of the nitrile corresponding to the amide. The method has the advantages of mild reaction conditions, high reaction selectivity, wide substrate applicability, simple post-treatment and energy consumption reduction.

Description

Method for preparing nitrile by bismuth complex-catalyzed amide dehydration

technical field

The present invention relates to a method for preparing nitriles from amides.

Background technique

Nitrile is an important chemical raw material and synthetic intermediate, which is widely used in the manufacture of medicines, synthetic fibers and plastics. For example, adiponitrile is the raw material for the preparation of nylon 66. Acrylonitrile is a monomer for the production of polyacrylonitrile, which is copolymerized with other monomers and can be used to produce synthetic rubber and engineering plastics. Benzonitrile is mainly used as an intermediate for advanced coatings such as benzo-substituted melamine, as well as an intermediate for the synthesis of pesticides, aliphatic amines, and benzoic acid, and as a solvent for nitrile-based rubber, resins, polymers, and coatings. Phenylacetonitrile is used to produce intermediates of medicine and pesticides such as phenylacetic acid, phenylethylamine, diphenylacetonitrile, β-phenylethyl alcohol, phenylacetaldehyde, α-chlorophenylacetate, etc. powder, penicillin, phenobarbital, etc. o-Toluonitrile can be used to synthesize agricultural fungicides pyraclostrobin, rust amine, fluorinamide, etc. Isopropyl benzonitrile can synthesize isopropyl aniline. o-Chlorobenzonitrile is mainly used in the synthesis of dye intermediates 2-cyano-4-nitroaniline, and in the pharmaceutical industry for the synthesis of antimalarial drugs such as nitroquine. Phthalonitrile can be used to synthesize phthalocyanine pigments and dyes, phthalosulfonamide drugs, xylene diisocyanate plastics, high thermal resistance polyamide fibers and desulfurization catalysts.

At present, the synthesis methods of nitriles mainly include the oxidative nitrification of alkanes, alkenes, aldols and amine substrates, the direct cyanation of alkanes, halogenated alkanes, and alkene substrates by using cyano sources as reagents, and the direct cyanation of amides, carboxylic acids ( esters) and dehydration nitrification of aldoxime substrates. Among these methods, the method for preparing the corresponding nitrile by amide dehydration has the advantages of low toxicity of the reaction reagent, water by-product of the reaction, high reaction selectivity, and high environmental and economic benefits.

The traditional method of amide dehydration to prepare nitrile is to use stoichiometric acid reagents (such as P ₄ O ₁₀ , POCl ₃ , SOCl ₂ , TiCl ₄ , etc.) and basic reagents (such as NaBH ₄ ) as dehydrating agents to promote amide dehydration. A large number of acidic or basic by-products are produced, which corrode equipment and put a lot of pressure on environmental protection; on this basis, scholars have developed a series of new catalysts, including hydrosilane dehydration system, high temperature catalytic system, palladium catalytic dehydration nitrification system, etc., among which , various transition metals or nitrenes catalyze the activation of Si-H bonds of hydrosilicides to form electrophilic silicon-hydrogen species, these reaction intermediates can promote the dehydration of primary amides to form nitriles, but are accompanied by the formation of hydrogen and monosilane during the reaction. base ether, which increases the difficulty of separation; in the absence of a dehydrating agent, the dehydration of amides to nitrile requires higher reaction temperatures (>160 °C), Campbell et al. (Campbell J, McdougaldG, Mcnab H, et al.Synthesis, 2007, 20:3179-3184) reported the dehydration performance of dehydrating agent 3A silicon dioxide and tungsten trioxide catalyzing amide and oxime under the condition of rapid vacuum pyrolysis, the reaction does not produce other by-products, but the reaction temperature is relatively high (300 ℃). above), only for thermally stable amides. Sueoka et al. (Sueoka S, Mitsudome T, Mizugaki T, et al. Chem Commun, 2010, 46: 8243-8245) reported a heterogeneous catalyst for amide dehydration based on hydrotalcite-supported monomeric vanadium oxide , the amide is dehydrated into nitrile by reflux reaction in mesitylene under the catalysis of 20mol% loading. The reaction temperature of this system is high (>160°C), the energy consumption is high and the separation difficulty of nitrile and solvent is increased.

The above-mentioned amide dehydration reaction in the absence of a dehydrating agent is assumed to be carried out at a conventional room temperature, which will result in the ineffective reaction.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for preparing nitrile by catalytic amide dehydration of bismuth complex under mild conditions.

In order to solve the above-mentioned technical problems, the present invention provides a method for preparing nitrile by bismuth complex catalyzed amide dehydration, comprising the following steps:

1), bismuth salt (trivalent bismuth salt) and ligand react (2 ± 0.5) hours at room temperature in solvent to obtain a solution containing bismuth complex;

The bismuth salt: ligand=1:1～5 molar ratio;

2), adding an amide to the solution containing the bismuth complex obtained in step 1), and reacting at room temperature and normal pressure for 6 to 18 hours, thereby realizing the dehydration of the amide to generate nitrile, and the bismuth complex is used as a catalyst;

The amide: the bismuth salt in step 1)=5～25:1 mol ratio;

3) The reaction solution obtained in step 2) is separated to obtain the crude product of the nitrile corresponding to the amide.

The improvement of the method for preparing nitrile as bismuth complex catalyzed amide dehydration of the present invention:

Step 3) The solvent, catalyst and unreacted amide obtained in the separation process are subjected to cyclic reaction.

As the further improvement of the method for preparing nitrile by catalyzing amide dehydration of bismuth complex of the present invention:

The bismuth salt is at least one of bismuth acetate (preferred), bismuth trifluoride, bismuth trichloride, bismuth tribromide, bismuth nitrate (preferred), bismuth sulfate, bismuth phosphate, and bismuth borate;

Ligands are diethylamine, triethylamine, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, pyridine, 2,2'-bipyridine, 1,10-o-phenanthroline, triphenylphosphine, tricyclic At least one of hexylphosphine and 1,1'-binaphthol.

As the further improvement of the method for preparing nitrile by catalyzing amide dehydration of bismuth complex of the present invention:

The amide in the step 2) is R-(CONH ₂ ) _X , and R is C _6-20 aryl, C _1-20 straight or branched alkyl, C _1-20 straight or branched alkenyl, C _1-20 straight or branched chain alkynyl, C _3-20 cycloalkyl, C _3-20 alkenyl, C _3-20 azacyclyl, C _{3-20 oxacyclyl} , C _3-20 sulfur Heterocyclyl; X is 1 or 2;

The group R may contain at least one (one or more) halogen, hydroxyl, carboxyl, carbonyl, amino, nitro, mercapto and other groups.

By way of example, the amide is any of the following: benzamide, 2-methylbenzamide, 3-methylbenzamide, 2,3-dimethylbenzamide, 2-nitro-4-carboxybenzene Formamide, 4-tert-butylbenzamide, 4-methoxybenzamide, 2-fluorobenzamide, 2-chlorobenzamide, 2-bromobenzamide, 4-hydroxybenzamide, 3 -Methoxybenzamide, 4-nitrobenzamide, 2-aminobenzamide, 2-thiophenecarboxamide, terephthalamide, phenylacetamide, naphthalene-1-carboxamide, quinoline-6 - Formamide, 4-pyridinecarboxamide, 2,5-furandicarboxamide, butanamide, isobutyramide, caproamide, succinamide, adipamide, dodecamide, octadecylamide, cyclohexylcarboxamide.

As the further improvement of the method for preparing nitrile by catalyzing amide dehydration of bismuth complex of the present invention:

The solvent in step 1) is at least one of methanol, ethanol, ethylene glycol, isopropanol, tetrahydrofuran, acetonitrile, ethyl acetate, cyclohexane, dichloromethane, 1,2-dichloroethane and toluene .

As a further improvement of the method for preparing nitrile by catalytic amide dehydration of bismuth complex of the present invention, the separation in step 3) is as follows: the reaction solution obtained in step 2) is rectified under reduced pressure, and the distillate is respectively the crude product of solvent, water and nitrile ; The bottom liquid contains catalyst and unreacted amide.

The crude nitrile can be further purified by conventional rectification to obtain the pure nitrile.

In the present invention, 1 mol of amide is generally matched with 0.5 to 1 L of solvent; room temperature refers to 15 to 35°C.

The amide conversion rate of step 2) of the present invention is not less than 95.0%. In step 3), the reaction solution is separated to obtain nitrile (crude product of nitrile) with a purity of ≥95.0%, and further purification to obtain a nitrile with a purity of ≥99.5%.

Compared with the prior art, the present invention has the following technical advantages:

(1) The preparation of the catalyst is simple. Under the catalysis of the bismuth complex, the corresponding nitrile is prepared from the amide without using a dehydrating agent, and the by-product is only water, which reduces the discharge of three wastes;

(2) The reaction is carried out in a homogeneous catalytic system, and the reaction efficiency is high;

(3) The reaction is carried out under mild conditions, the reaction selectivity is high, the substrate applicability is wide, the post-processing is simple, and the energy consumption is reduced.

Detailed ways

The technical solutions of the present invention will be further described below according to specific embodiments. The protection scope of the present invention is not limited to the following examples, which are listed for illustrative purposes only and do not limit the present invention in any way.

Embodiment 1-1, a kind of bismuth complex catalyzed the method for the efficient dehydration of benzamide to prepare benzonitrile, carry out the following steps successively:

(1), in reaction vessel, first 3mol triethylamine is dissolved in the methanol of 10L, must contain the methanol solution of triethylamine;

Then 1 mol of bismuth acetate was dissolved in the methanol solution containing triethylamine, and stirred at room temperature for 2 h to obtain a solution containing bismuth complex; the bismuth complex was used as a catalyst;

(2) 15mol of benzamide was added to the above-mentioned reactor, and the reaction was stirred at normal pressure and room temperature for 12 hours; the reacted material (reaction solution) was obtained.

(3) The material after the reaction of step (2) gained is analyzed by GC, and the conversion rate of the raw material (benzamide) is 98.8%, and the selectivity is 99.8%;

The materials after the above-mentioned reaction are separated according to the following conditions: carry out rectification under reduced pressure (2.0kPa～5.0kPa), and the distillate successively obtains methanol, water, and benzonitrile crude products (fractions of about 80～100° C.), and the bottom liquid It is a mixture of catalyst, unreacted benzamide, etc. The purity of crude benzonitrile was 95.0%.

The benzonitrile crude product is further purified by conventional rectification to obtain the benzonitrile product. The purity of the benzonitrile product is more than 99.5%, and the yield is 96.5%. The formula for calculating the yield of benzonitrile is:

Wherein, Y---product yield;

M ₁ - the actual output of benzonitrile;

M ₂ ——the theoretical yield of benzonitrile.

Embodiment 1-2, the catalyst circulation is applied mechanically:

The first cycle is applied mechanically: after the reaction of Example 1, the addition of benzamide and methyl alcohol is added in the bottom liquid, methanol of the separated gained, until the total amount of the benzamide contained in the benzamide added and the bottom liquid is 15mol, and The total amount of methanol is 10L (that is, the same as the amount used in Example 1-1), and the rest are the same as in Example 1-1. When the reaction time is 12h, the conversion rate of benzamide is 98.6%, the reaction selectivity is 99.8%, the product yield is 96.3%, and the product purity is 99.0%.

Note: Generally, it is necessary to detect the content of benzamide in the bottom liquid of the kettle in advance.

By repeating the above cycle, at the eighth time, the benzamide conversion rate was 95.2%, the reaction selectivity was 99.0%, the product yield was 92.0%, and the product purity was 98.0%. At this time, there are many impurities in the reaction system, which reduces the product purity and is no longer recycled.

Embodiment 2～5, change the molar ratio of ligand and bismuth acetate in the catalyst, the consumption of bismuth acetate remains unchanged; other operations are equivalent to embodiment 1-1, obtain embodiment 2～5, process parameter and reaction result refer to table 1.

Table 1

Example Molar ratio of ligand to bismuth acetate Raw material conversion rate (%) Reaction selectivity (%) Product yield (%) 2 1:1 95.1 99.8 92.5 3 2:1 97.8 99.8 95.2 4 4:1 99.3 99.8 97.0 5 5:1 99.5 99.8 97.1

Examples 6-12, changing the type of bismuth salt, the consumption of bismuth salt remains unchanged, still 1mol, other operations are equivalent to embodiment 1-1, obtain embodiment 6-12, process parameter and reaction result refer to Table 2.

Table 2

Example Types of Bismuth Salts Raw material conversion rate (%) Reaction selectivity (%) Product yield (%) 6 Bismuth sulfate 96.5 99.8 94.8 7 Bismuth trifluoride 97.1 99.8 95.0 8 Bismuth trichloride 97.5 99.8 95.3 9 Bismuth tribromide 97.2 99.8 95.8 10 Bismuth nitrate 98.3 99.8 96.1 11 Bismuth Phosphate 97.8 99.8 95.2 12 Bismuth borate 98.6 99.8 96.3

In Examples 13-22, the types of ligands were changed, and the amount of the ligand remained unchanged at 3 mol. Other operations were equivalent to those of Example 1-1, and Examples 13-22 were obtained.

table 3

Example Ligand species Raw material conversion rate (%) Reaction selectivity (%) Product yield (%) 13 Diethylamine 98.5 99.8 95.8 14 Ethylenediamine 98.1 99.8 95.4 15 Diethanolamine 98.8 99.8 96.3 16 Triethanolamine 99.2 99.8 96.8 17 Pyridine 98.3 99.8 95.1 18 2,2'-bipyridine 98.8 99.8 96.2 19 1,10-phenanthroline 98.6 99.8 96.1 20 Triphenylphosphine 98.9 99.8 96.5 twenty one tricyclohexylphosphine 98.2 99.8 95.7 twenty two 1,1'-Binaphthol 98.5 99.8 96.0

In Examples 23-50, the types of amides were changed, and the amount of amides remained unchanged at 15 mol. Other operations were identical to those in Example 1-1, and Examples 23-50 were obtained. See Table 4 for process parameters and reaction results.

Table 4

Embodiment 51～54, change the molar ratio of amide and bismuth acetate, the consumption of bismuth acetate remains unchanged, still is 1mol, other operations are equivalent to embodiment 1-1, obtain embodiment 51～54, process parameter and reaction result refer to table 5.

table 5

Example Molar ratio of amide to bismuth acetate Raw material conversion rate (%) Reaction selectivity (%) Product yield (%) 51 5:1 99.1 99.8 97.0 52 10:1 99.0 99.8 96.8 53 20:1 97.5 99.8 95.0 54 25:1 95.5 99.8 93.1

In Examples 55 to 63, the type of solvent was changed, and the volume and dosage remained unchanged; other operations were identical to those of Example 1-1, and Examples 55 to 63 were obtained. See Table 6 for process parameters and reaction results.

Table 6

Example Type of solvent Raw material conversion rate (%) Reaction selectivity (%) Product yield (%) 55 Ethanol 98.5 99.8 95.8 56 Ethylene Glycol 98.7 99.8 96.2 57 isopropyl alcohol 98.4 99.8 95.7 58 tetrahydrofuran 98.5 99.8 95.9 59 Acetonitrile 97.8 99.8 95.0 60 Cyclohexane 95.5 99.8 92.7 61 Dichloromethane 97.8 99.8 95.3 62 1,2-Dichloroethane 96.4 99.8 93.8 63 Toluene 98.2 99.8 95.0

In Examples 64 to 69, the reaction time of step 2) was changed, and other operations were the same as those in Example 1-1 to obtain Examples 64 to 69. The process parameters and reaction results are shown in Table 7.

Table 7

Comparative example 1, only add bismuth acetate in the reaction system, do not add ligand;

That is, be specifically: (1), in reaction vessel, add the bismuth acetate of 1mol and the methanol of 10L; Then immediately carry out subsequent steps;

The subsequent steps are the same as in Example 1-1.

The conversion of benzamide was only 35.5%, and the yield of benzonitrile was only 31.8%.

Comparative example 2, cancel the stirring at room temperature of step (1) for 2h,

That is, be specifically: (1), in reaction vessel, add the methanol of 3mol triethylamine, 1mol of bismuth acetate and 10L; Then immediately carry out subsequent steps;

The subsequent steps are the same as in Example 1-1.

The conversion of benzamide was only 75.2%, and the yield of benzonitrile was only 70.5%.

Finally, it should also be noted that the above enumeration is only a few specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many modifications are possible. All deformations that those of ordinary skill in the art can directly derive or associate from the disclosure of the present invention shall be considered as the protection scope of the present invention.

Claims (6)

1. the method for preparing nitrile by bismuth complex catalyzed amide dehydration is characterized in that comprising the following steps: 1), bismuth salt and ligand react at room temperature in solvent for (2 ± 0.5) hours to obtain a solution containing bismuth complex; The bismuth salt: ligand=1:1～5 molar ratio; 2), adding an amide to the solution containing the bismuth complex obtained in step 1), and reacting at room temperature and normal pressure for 6-18 hours, thereby realizing dehydration of the amide to generate nitrile, and the bismuth complex is used as a catalyst; The amide: the bismuth salt in step 1)=5～25:1 mol ratio; 3) The reaction solution obtained in step 2) is separated to obtain the crude product of the nitrile corresponding to the amide. 2. the method for preparing nitrile by bismuth complex catalytic amide dehydration according to claim 1, is characterized in that: Step 3) The solvent, catalyst and unreacted amide obtained in the separation process are subjected to cyclic reaction. 3. bismuth complex catalyzed amide dehydration according to claim 1 and 2 prepares the method for nitrile, it is characterized in that in described step 1): The bismuth salt is at least one of bismuth acetate, bismuth trifluoride, bismuth trichloride, bismuth tribromide, bismuth nitrate, bismuth sulfate, bismuth phosphate, and bismuth borate; Ligands are diethylamine, triethylamine, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, pyridine, 2,2'-bipyridine, 1,10-o-phenanthroline, triphenylphosphine, tricyclic At least one of hexylphosphine and 1,1'-binaphthol. 4. the method for preparing nitrile by bismuth complex catalytic amide dehydration according to claim 3, is characterized in that: The amide in the step 2) is R-(CONH ₂ ) _X , and R is C _6-20 aryl, C _1-20 straight or branched alkyl, C _1-20 straight or branched alkenyl, C _1-20 straight or branched chain alkynyl, C _3-20 cycloalkyl, C _3-20 alkenyl, C _3-20 azacyclyl, C _{3-20 oxacyclyl} , C _3-20 sulfur Heterocyclyl; X is 1 or 2; The group R contains at least one halogen, hydroxyl, carboxyl, carbonyl, amino, nitro and mercapto. 5. the method for preparing nitrile by bismuth complex catalyzed amide dehydration according to any one of claims 1 to 4, is characterized in that: The solvent in the step 1) is at least one of methanol, ethanol, ethylene glycol, isopropanol, tetrahydrofuran, acetonitrile, ethyl acetate, cyclohexane, dichloromethane, 1,2-dichloroethane and toluene. A sort of. 6. the method for preparing nitrile by bismuth complex catalytic amide dehydration according to claim 1～5, it is characterized in that the separation in described step 3) is: step 2) the reaction solution obtained by vacuum distillation, distillate They are the crude products of solvent, water and nitrile respectively; the bottom liquid contains catalyst and unreacted amide.