JPH07316120A - Production of 2-phenylbytyronitrile - Google Patents

Abstract

PURPOSE:To easily obtain 2-phenylbutyronitrile in an industrial scale at a low cost by using zeolite carrying an impregnated alkali metal as a catalyst and reacting phenylacetonitrile with diethyl carbonate in a gaseous phase. CONSTITUTION:Phenylacetonitrile is reacted with diethyl carbonate in a gaseous phase using zeolite carrying an impregnated alkali metal (a zeolite carrying an alkali metal fixed by a method except an ion exchanging method) as a catalyst to obtain 2-phenylbutyronitrile. Since this method does not use a halide, there is no problem caused by the halide such as the corrosion of an apparatus and the treatment of waste liquid. Further, the method has high selectivity in producing 2-phenylbutyronitrile. The catalyst is solid and the reaction system is the gaseous phase, so the objective product can be easily separated from the catalyst and other compounds after finishing the reaction. The operation is simple and the cost is low. The catalyst is inexpensive, easy to handle and capable of being reused. The compound is useful as an intermediate for synthesizing medicines.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 2-phenylbutyronitrile, more specifically,
Using a zeolite impregnated with an alkali metal as a catalyst,
The present invention relates to a method for producing 2-phenylbutyronitrile by reacting phenylacetonitrile with diethyl carbonate in a gas phase.

[0002]

2. Description of the Related Art 2-Phenylbutyronitrile (PhCH
(Et) CN) is a synthetic intermediate for various pharmaceuticals.
It is also a useful compound as a solvent of an electrolyte for electrochromic windows. Therefore, it is desired to be manufactured by an inexpensive and simple method.

A typical method for producing 2-phenylbutyronitrile is ethylation of phenylacetonitrile. 2 by ethylation of phenylacetonitrile
-A method for producing phenylbutyronitrile includes (1)
A method of reacting phenylacetonitrile with ethanol in the presence of metallic sodium, (2) Phenylacetonitrile and ethyl halide in the presence of a catalyst,
A method of reacting in a strong base solution has been reported.

The method (1) is described in Japanese Examined Patent Publication No. 43-29579, which is a method in which sodium metal is added to ethanol and dissolved by heating, and then the solution is dissolved in an autoclave together with phenylacetonitrile and ethyl acetate. The reaction is followed by ether extraction to produce ethylphenylacetonitrile, that is, 2-phenylbutyronitrile (yield 62.5%).

The method (2) has been reported as follows. (I) JP-A-56-163757 discloses that a liquid phase heterogeneous catalyst comprising a quaternary ammonium salt is used, and phenylacetonitrile and ethyl bromide are converted into ethylphenyl in the presence of sodium hydroxide and water. A method of making acetonitrile is described. (Ii) JP-A-57-185252 discloses that a catalyst represented by the general formula R ₁ O (C ₂ H ₄ O) _m (C ₃ H ₆ O) _n R ₂ is used and potassium hydroxide and water are used. In the presence of phenylacetonitrile and ethyl bromide to produce 2-phenylbutyronitrile. (Iii) Furukawa et al. Used a tetrakis (alkylsulfinylmethyl) methane or a sulfoxide derivative as a catalyst, and in a liquid-liquid two-phase system, in the presence of an aqueous sodium hydroxide solution, phenylacetonitrile and 2-bromoethyl / iodide A method for producing phenylbutyronitrile has been reported ("Sulfoxide, a new type of phase transfer catalyst in two-phase alkylation" Chemistry Le
tters, pp.1421-1424, 1982, "Sulfoxide-substituted pyridines as phase transfer catalysts for nucleophilic substitution and alkylation," J. Chem. Soc. Perkin Trans. I pp.1833-1838, 19
84, "A New Type of Phase Transfer Catalyst for Nucleophilic Substitution and Alkylation: Tetrakis-Sulfoxide" J. Chem. So
c. Perkin Trans. I pp.333-336, 1986).

[0006]

However, the above method (1) is not suitable for industrial use because it uses metallic sodium, the reaction is a liquid phase system, and the operation is complicated. .

On the other hand, in the method (2), although the reaction time is shortened and the yield of 2-phenylbutyronitrile is improved, the inorganic halide is equimolar to the target 2-phenylbutyronitrile. (Sodium halide or potassium halide) is co-produced, and a halide is also produced by a side reaction. These inorganic or organic halides cause problems such as equipment corrosion and waste disposal. In addition, the above-mentioned methods have problems that the separation operation of the catalyst and the product is complicated and the reuse of the catalyst is difficult because all of them are liquid phase reactions. Therefore, there is a cost. Therefore, the method (2) is not suitable for industrial use.

Therefore, 2 from phenylacetonitrile
A simple method for producing phenylbutyronitrile has been desired.

[0009]

The present invention is a process for producing 2-phenylbutyronitrile characterized in that phenylacetonitrile and diethyl carbonate are reacted in a gas phase using a zeolite impregnated with an alkali metal as a catalyst. Is provided.

In a preferred embodiment of the present invention, a method for producing 2-phenylbutyronitrile is characterized in that phenylacetonitrile and diethyl carbonate are reacted in a gas phase using a zeolite impregnated with sodium or potassium as a catalyst, It is characterized in that ion exchange is performed with an alkali metal ion, and then phenylacetonitrile and diethyl carbonate are reacted in a gas phase using a zeolite impregnated with an alkali metal which may be different from the above as a catalyst.
-Method for producing phenylbutyronitrile, NaX-K, N
aY-Na, K-USY-Na, KL-Na, Na-H
A method for producing 2-phenylbutyronitrile, which comprises reacting phenylacetonitrile and diethyl carbonate in a gas phase using a catalyst composed of one or more kinds of SM-Na. Here, X represents X-type zeolite, Y represents Y-type zeolite, USY represents USY-type zeolite, L represents L-type zeolite, and HSM represents high silica mordenite. Further, for example, NaX-K is a catalyst in which potassium is impregnated and supported after ion-exchange of X-type zeolite with sodium ions.

The reaction according to the present invention is carried out by the following formula: PhCH ₂ CN + EtO (CO) OEt → PhC
It is a reaction represented by H (Et) CN + EtOH + CO ₂ .

In the present invention, diethyl carbonate is used as the ethylating agent. 2-Phenylbutyronitrile cannot be produced using ethanol.

The catalyst used in the present invention is a zeolite impregnated and supported with an alkali metal. As the zeolite, either natural or synthetic zeolite can be used. For example,
Examples of natural zeolites include chyabasite, erionite, faujasite, mordenite and the like.
On the other hand, examples of the synthetic zeolite include X-type zeolite, Y-type zeolite, L-type zeolite, USY-type zeolite, and mordenite. Among these, X-type zeolite, Y-type zeolite, L-type zeolite, USY-type zeolite, and high silica mordenite (HSM) are preferable because of the selectivity of 2-phenylbutyronitrile. Zeolites have a unique shape selectivity, and it is considered that the shape selectivity shows a high selectivity for 2-phenylbutyronitrile.

Alkali metals include Li, Na, K, Rb,
Either Cs or Fr may be used, but Na and K are particularly preferable from the viewpoint of selectivity of 2-phenylbutyronitrile and proper basic strength. The alkali metal may be impregnated and supported in an ionic form, or may be impregnated and supported in a metal form.

Any combination of zeolite and alkali metal may be used, but X-Na, X-K, and X-Na may be selected depending on the selectivity of 2-phenylbutyronitrile and proper basic strength.
Y-Na, Y-K, USY-Na, USY-Ce, L-
Na, HSM-Li, HSM-K and HSM-Na are preferred.

As used herein, the term "zeolite impregnated with an alkali metal" refers to a method other than the ion exchange method,
It is a zeolite in which an alkali metal is fixedly supported. The alkali metal may be in ionic or metallic form. As a method for impregnating and carrying an alkali metal, an existing known method can be applied without particular limitation. Specifically, there are a method of supporting an alkali metal compound, a method of supporting an alkali metal element, a method of supporting both of them, and the like.

As a method of supporting the alkali metal compound, (1) the zeolite is immersed in an aqueous solution of a soluble alkali metal compound, for example, sodium carbonate, and heated in a hot water bath with stirring to gradually evaporate the water, and the zeolite Method of uniformly drying sodium carbonate on top (afterwards, it is possible to desorb carbonate ions as carbon dioxide gas by firing in a stream of air or the like), (2) put zeolite in an evaporator and stir However, there is a method of spraying and impregnating a solution of an alkali metal compound while constantly keeping the zeolite in a dry state by exhausting. In these cases, part of the alkali metal is supported by ion exchange.

As a method for supporting an alkali metal element, for example, zeolite is exhausted at a high temperature, then cooled to room temperature under an inert gas such as nitrogen, alkali metal pieces such as sodium metal are added and exhausted, and then dry ice is used. There is a method in which ammonia gas is added at an ethanol temperature to dissolve the alkali metal pieces with liquid ammonia, and then the ammonia is desorbed by heating and exhausting.

Another method is disclosed in JP-A-50-
A method for supporting both sodium hydroxide and metallic sodium described in Japanese Patent No. 3274, J. Am. Chem. Soc., 1960,
82 , p.387, a method of introducing and supporting an alkali metal in a gaseous state on a catalyst can be mentioned.

The amount of the alkali metal supported is not particularly limited, but when it is introduced in an amount of more than 20% by weight based on the total amount of the zeolite catalyst, it is deactivated in the production reaction of 2-phenylbutyronitrile although the initial yield is high. May be intense.
Therefore, the upper limit of the amount of the alkali metal supported is preferably 20% by weight, more preferably 10% by weight, and the lower limit is preferably 0.2% by weight, more preferably 1.0% by weight, based on the total amount of the catalyst. . The amount of alkali metal supported by the impregnated carrier of the present invention was larger than the ion exchange capacity by the ion exchange method, which was confirmed by elemental analysis.

In the present invention, from the viewpoint of the productivity of 2-phenylbutyronitrile, it is preferable to impregnate and carry the alkali metal using zeolite that has been ion-exchanged with the alkali metal ion in advance. That is, the preferred zeolite catalyst used in the present invention is ion-exchanged with alkali metal ions,
Next, a zeolite catalyst impregnated with an alkali metal, which may be different from the above, is carried. In this case, the alkali metal ion-exchanged zeolite used is NaX, NaY, KU.
SY, KL and Na-HSM are preferred.

The method for preparing the alkali metal ion-exchanged zeolite is not particularly limited, and existing known methods can be applied.
As an example, a method of adding an alkali metal compound aqueous solution to zeolite and performing ion exchange can be mentioned, but other methods may be used. The alkali metal ion compound may be any of chlorides, bromides, iodides, hydroxides and the like of alkali metals.

In the zeolite catalyst which is ion-exchanged with an alkali metal ion and then impregnated with an alkali metal, any combination of zeolite and alkali metal may be used, but the selectivity of 2-phenylbutyronitrile and the appropriate basic strength are sufficient. From the above, NaX-K, NaY-Na, K
-USY-Na, K-USY-Cs, KL-Na, Na
-HSM-Li and Na-HSM-Na are preferred, and N
aX-K, NaY-Na, K-USY-Na, KL-N
a and Na-HSM-Na are particularly preferred.

In the method of the present invention, the above zeolite catalyst is charged into a reactor, and phenylacetonitrile and diethyl carbonate are introduced into the reactor to carry out the reaction in the gas phase. As the reaction device, any device may be used as long as it can carry out the reaction in the gas phase. The inflow of phenylacetonitrile and diethyl carbonate may be two or more, and other carrier gas such as nitrogen gas may be used, but an inert gas is preferable as the carrier gas.
Regarding the molar ratio of phenylacetonitrile and diethyl carbonate in the inflow, the lower limit is preferably diethyl carbonate 0.5 to acetonitrile 1, more preferably 1, and the upper limit is preferably acetonitrile 1 to diethyl carbonate 3 and 2 is 2. More preferable. This is because the yield and selectivity of 2-phenylbutyronitrile decrease if it is out of this range. From the viewpoint of reaction efficiency, the flow velocity is the weight space velocity (W.
H. S. V. ), The lower limit is preferably 0.05 hours ^-1 ,
0.2 hours- ¹ is more preferable, and the upper limit is preferably 5 hours- ^{1 and} more preferably 2 hours- ¹ . The reaction temperature and reaction pressure may be any as long as the system is kept in the gas phase. Specifically, the following reaction temperature and reaction pressure are preferable from the viewpoint of reaction efficiency. The lower limit of the reaction temperature is preferably 200 ° C, more preferably 220 ° C, and the upper limit is preferably 450 ° C, more preferably 350 ° C. Upper limit of reaction pressure is 3
kg / cm ² G is preferable, 2 kg / cm ² G is more preferable,
The lower limit may be 0 kg / cm ² G.

According to the method of the present invention, since the halide is not used in the reaction system, the problems caused by the halide, such as corrosion of the apparatus and treatment of waste liquid, do not occur. Furthermore, since the catalyst is a solid and the reaction system is in a gas phase, the target product can be easily separated from the catalyst and other compounds after the reaction, for example, by only distillation separation. Therefore, the operation is simple, the productivity of 2-phenylbutyronitrile per catalyst can be improved, and the cost is low. The catalyst used is inexpensive, easy to handle, and reusable. Further, there is almost no by-product of diethylphenylacetonitrile, and the selectivity of 2-phenylbutyronitrile is high.

Further, the method of the present invention shows superior conversion of phenylacetonitrile, yield of 2-phenylbutyronitrile and selectivity as compared with the case where a zeolite catalyst ion-exchanged with alkali metal ions is used. Therefore,
The production method of the present invention is very useful for industrially producing 2-phenylbutyronitrile.

[0027]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

Preparation of Catalyst (Preparation Example 1) a) X-type zeolite (extruded product, Molecular Sieve 13X manufactured by Union Showa Co., Ltd.) was finely pulverized by a ball mill until the particle size became 20 μm or less. To 100 g of this powder, 10 times equivalent of 1N sodium chloride aqueous solution (exchange solution) was added and stirred at 90 ° C. for 2 hours. The centrifuge was used to separate the exchange liquid from the zeolite. The same amount of new exchange liquid was added again, and the above operation was repeated 10 times in total, followed by washing with water until no chlorine ion was detected in the washing liquid by the qualitative analysis method using silver nitrate. After washing with water, the zeolite is dried at 100 ° C for 3 hours and then at 500 ° C for 3 hours.
Baking for an hour, sodium ion exchange type zeolite (Na
X) was obtained.

B) To 100 g of this NaX, 0.2 equivalent of 0.01N potassium carbonate aqueous solution was added, and ion-exchanged water was added little by little while heating on a water bath so that potassium carbonate was uniformly dispersed. While stirring, the mixture was gradually evaporated to dryness. After that, it is dried at 120 ℃ for 2 hours, then 500 ℃
NaX impregnated with potassium ions and baked for 3 hours
(NaX-K) was prepared. This NaX-K is 3 mm x
It was molded into pellets of 3 mmφ.

(Preparation Example 2) Sodium ion exchange Y type was used in the same manner as in Preparation Example 1a) except that Y-type zeolite (powder type, TSZ-320 manufactured by Tosoh Corporation) was used and fine pulverization by a ball mill was omitted. Zeolite (NaY)
Was prepared. Then, using NaY prepared above,
NaY (NaY—Na) impregnated with sodium ions was prepared in the same manner as in Preparation Example 1b) except that 0.15 times equivalent of 0.01 N sodium carbonate aqueous solution was used.
Pelletized.

Preparation Examples 3 to 4 Preparation examples except that USY type zeolite (powder type, TSZ-330 manufactured by Tosoh Corporation) was used, fine grinding by a ball mill was omitted, and potassium chloride was used instead of sodium chloride. 1a), potassium ion exchange USY type zeolite (K-
USY) was prepared. Then, the K-US prepared above
K-USY impregnated with sodium ions (K-USY-Na) was carried out in the same manner as in Preparation Example 1b) except that Y was used and a 0.10 times equivalent amount of a 0.01 N sodium carbonate aqueous solution or a cesium carbonate aqueous solution was used. ), K-USY impregnated with cesium ions (K-USY-Cs) is prepared,
Pelletized.

(Preparation Example 5) Mordenite (powder type, TSZ-600 manufactured by Tosoh Corp.) was used in an amount of 10 times equivalent of 2.
The mixture was stirred in a normal hydrochloric acid aqueous solution (exchange solution) at 80 ° C for 1.5 hours. Using a centrifuge, the mordenite and the exchange liquid were separated, the same amount of new exchange liquid was added again, and the above operation was repeated 10 times in total. Then, it was washed with water and dried in the same manner as in Preparation Example 1a) to prepare a proton mordenite (HM). 6 this HM under steam of 10-20%
Steam treatment was performed at 00 to 700 ° C. for 3 hours. Then 1
Aluminum was extracted by stirring at 90 ° C. for 8 hours in a 0-fold equivalent of 12 N hydrochloric acid aqueous solution, and then washed with water and dried in the same manner as in Preparation Example 1a). Finally, steam treatment was performed at 700 ° C. for 3 hours under 10% steam. In this way, high silica mordenite (H—H) ion-exchanged with protons having a silica / alumina molar ratio of 114.
SM (114)) was prepared. This H-HSM (11
4) To 100 g, 10 times equivalent of 1N sodium chloride aqueous solution was added, and the mixture was stirred at 90 ° C. for 2 hours. Using a centrifuge, separate the mordenite and the exchange liquid, add the same amount of a new exchange liquid again, repeat the above operation 15 times in total, wash with water and dry in the same manner as in Preparation Example 1a), Ion exchange high silica mordenite (Na-HSM (11
4)) was prepared.

Next, the Na-HSM (1
14) was used and in the same manner as in Preparation Example 1b) except that 0.3 times equivalent of 0.01N sodium carbonate aqueous solution was used,
Na-HSM impregnated with sodium ions (11
4) (Na-HSM (114) -Na) was prepared and pelletized.

(Preparation Example 6) HM prepared above is 10
Steamed at 600-700 ° C. for 3 hours under 20% steam. Next, aluminum is extracted by stirring at 90 ° C. for 8 hours in 10 times equivalent of 6N hydrochloric acid aqueous solution,
Then, it was washed with water and dried in the same manner as in Preparation Example 1a). Finally, steam treatment was performed at 700 ° C. for 3 hours under 10% steam. Thus, high silica mordenite (H-HSM (65)) ion-exchanged with protons having a silica / alumina molar ratio of 65 was prepared.
This H-HSM (65) was ion-exchanged in the same manner as in Preparation Example 5 to prepare sodium ion-exchanged high silica mordenite (Na-HSM (65)). Then, Na-HSM impregnated with lithium ions was carried out in the same manner as in Preparation Example 1b) except that the Na-HSM (65) prepared above was used and 0.4 times equivalent of 0.01N lithium carbonate aqueous solution was used. -HSM (65) (Na-HSM (65) -L
i) was prepared and pelletized.

(Preparation Example 7) The HM prepared above was mixed with 10
Steamed at 600-700 ° C. for 3 hours under 20% steam. Next, aluminum was extracted by stirring at 90 ° C. for 18 hours in a 10-fold equivalent of 12N aqueous hydrochloric acid solution, and then washed with water and dried in the same manner as in Preparation Example 1a). Finally, steam treatment was performed at 700 ° C. for 3 hours under 10% steam. Thus, high silica mordenite (H-HSM (185)) ion-exchanged with proton having a silica / alumina molar ratio of 185 was prepared. This H-HSM (185) was ion-exchanged in the same manner as in Preparation Example 5 to prepare sodium ion-exchanged high silica mordenite (Na-HSM (185)). Then, using Na-HSM (185) prepared above,
Na-HSM (185) (Na-H) impregnated with sodium ions was carried out in the same manner as in Preparation Example 1b) except that 0.05 times the equivalent of 0.01 N sodium carbonate aqueous solution was used.
SM (185) -Na) was prepared and pelletized.

Preparation Example 8 Instead of the X-type zeolite, an L-type zeolite (powder type, manufactured by Tosoh Corp. TSZ-
500) was used, and the fine grinding by a ball mill was omitted, and potassium ion-exchanged L-type zeolite (KL) was prepared in the same manner as in Preparation Example 1a) except that potassium chloride was used instead of sodium chloride. Then, using the KL prepared above, KL (KL-Na) impregnated with sodium ions was carried out in the same manner as in Preparation Example 1b) except that 0.3 times equivalent of 0.01 N sodium carbonate aqueous solution was used. Prepared,
Pelletized.

(Preparation Examples 9 to 10 for comparison) Hydrogen ion exchange X was carried out in the same manner as in Preparation Example 1a) except that ammonium chloride or magnesium chloride was used instead of sodium chloride.
Type zeolite (HX) and magnesium ion-exchanged X type zeolite (MgX) were prepared and pelletized.

(Preparation Examples 11 to 12: For Comparison) The same procedure as in Preparation Examples 9 and 10 was repeated except that Y-type zeolite (powder type, TSZ-320 manufactured by Tosoh Corporation) was used instead of X-type zeolite. Hydrogen ion exchange Y-type zeolite (H
Y), magnesium ion-exchanged Y-type zeolite (Mg
Y) was prepared and pelletized.

(Preparation Example 13: Comparative) For 100 g of alumina (N613N manufactured by JGC Chemical Co., Ltd.), 2.0 times equivalent of 0.
In the same manner as in Preparation Example 2, an aqueous solution of 01N sodium carbonate was added to prepare alumina (Al ₂ O ₃ —Na) impregnated with sodium ions.

Reaction (Example 1) NaX-K10 prepared above as a catalyst
g was charged into a fixed-bed reaction tube made of SUS316 (internal diameter 15 mm, length 600 mm), and pretreatment was performed at 480 ° C. for 1 hour under an air stream of 1 atm. Then, diethyl carbonate (DEC) / phenylacetonitrile (PAN) molar ratio of 1.5, PAN partial pressure of 0.30 atm, DEC partial pressure of 0.
45 atm, N ₂ partial pressure 0.25 atm, W. H. S. V.
A 2-phenylbutyronitrile (PNB) synthesis reaction was performed under the conditions of 0.4 hours ^-1 and 250 ° C. The product was analyzed by gas chromatography. The results are shown in Table 1 below.

(Examples 2 to 9) Using the catalysts and reaction conditions shown in Table 1, a PBN synthesis reaction was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0042]

[Table 1]

Comparative Examples 1 to 4 NaX or K-USY prepared above was molded into pellets of 3 mm × 3 mmφ. As a catalyst, NaX or KU molded into pellets
Fixed bed reaction tube made of SUS316 (15m inside diameter)
m, length 600 mm) and fired at 480 ° C. for 1 hour in an air stream of 1 atm as a pretreatment. Then, diethyl carbonate (DEC) / phenylacetonitrile (PA
N) Molar ratio 1.5, PAN partial pressure 0.36 atm, DE
C partial pressure 0.54 atm, N ₂ partial pressure 0.10 atm, and 2-phenylbutyronitrile (PN
B) A synthetic reaction was performed. The results are shown in Table 2.

[0044]

[Table 2]

(Comparative Examples 5 to 13) Instead of NaX-K,
HX, HY, MgX, MgY, HM and H-HSM prepared above, and M, which is a metal oxide showing solid basicity.
A 2-phenylbutyronitrile synthesis reaction was carried out using gO, ZrO ₂ and Al ₂ O ₃ in the same manner as in Example 1. However, the formation of 2-phenylbutyronitrile was not detected.

Comparative Example 14 Example 1 was repeated except that the Al ₂ O ₃ —Na prepared above was used instead of NaX—K.
A 2-phenylbutyronitrile synthesis reaction was carried out in the same manner as in. Formation of 2-phenylbutyronitrile was observed very early after the start of the reaction, but the catalyst was rapidly deactivated, and 2-phenylbutyronitrile was not formed at all 2 hours after the start of the reaction.

[0047]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a simple industrially useful method for producing 2-phenylbutyronitrile from phenylacetonitrile and diethyl carbonate in a gas phase. Since the method of the present invention does not use a halide in the reaction system, it is caused by the halide.
Problems such as equipment corrosion and waste liquid treatment do not occur.
Furthermore, the selectivity of 2-phenylbutyronitrile is high, and since the catalyst is a solid and the reaction system is in the gas phase, the target product can be easily separated from the catalyst and other compounds after the reaction. Is simple and the cost is low. The catalyst used is inexpensive, easy to handle, and reusable.

Claims (1)

[Claims] 1. A method for producing 2-phenylbutyronitrile by ethylating phenylacetonitrile,
Using a zeolite impregnated with an alkali metal as a catalyst,
A method for producing 2-phenylbutyronitrile, which comprises reacting phenylacetonitrile with diethyl carbonate in a gas phase.