JP3500794B2 - Method for producing 2-cyanobiphenyls - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 2-cyanobiphenyls which are useful as intermediates for medical and agricultural chemicals and liquid crystal raw materials.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as methods for synthesizing 2-cyanobiphenyls. (1) Method by Ullman reaction using aromatic iodine compound and copper (
(JP-A-4-257564) (2) Method for coupling organic zinc, boron or tin compound with 2-halobenzonitrile in the presence of Pd complex catalyst
(JP-A-5-97813, JP-A-6-234690, JP-A-4-330073) (3) A method of coupling chlorobenzenes and 2-chlorobenzonitrile in the presence of a Ni catalyst and a metal powder (JP-A-2-15036 , 6-65153)

However, the method (1) is not suitable as an industrial method because the raw materials are expensive and the selectivity of the reaction is not sufficient. Also in the method (2), the raw materials and the catalyst are relatively expensive, and there are problems in handling and treating the organometallic compound and the like. The method of (3) is a reaction suitable for homocoupling as described in J. Org. Chem., Vol51.2627 (1986), and although improvements have been made, by-product homocoupling Generation suppression,
There is a problem of separation and removal, and there is a problem of treatment of waste metal and metal salt that are produced in large quantities after the reaction.

Meanwhile, the cinnamic acid derivative and the diene Diel
As a method of synthesizing a tetrahydrobiphenyl skeleton by the s-Alder reaction and aromatic cyclizing it, J. Am. Chem.
c., vol 65, 356 (1943), but when the diene is butadiene, the yield is extremely low, and it does not suggest the present invention. US PAT.5,138069 also suggests the possibility of this method, but there is no detailed explanation. Also, J.Org.
Chem., Vol55., 2545 (1990) describes the synthesis of 2-cyanobiphenyls by the Diels-Alder reaction of benzylidene malon nitrile and butadienylmorpholine. There is an industrial problem.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrial method for selectively producing 2-cyanobiphenyls by using inexpensive raw materials and without causing problems such as waste.

[0006]

[Means for Solving the Problems]
As a result of repeated research on the production method of cyanobiphenyls, the reactivity of α-cyanocinnamic acid esters with respect to butadiene is significantly higher than that of α-unsubstituted cinnamic acid derivatives, and high yields and high selectivity can be obtained. 2-cyano-2 which is a chemical adduct
-We found that it gave alkoxycarbonyltetrahydrobiphenyls and then hydrolyzed it to produce 2-cyanobiphenyls easily by decarboxylation and dehydrogenation of 2-cyano-2-carboxytetrahydrobiphenyls. The inventors have found what can be done and have completed the present invention.

That is, the present invention relates to 2-
The present invention relates to a method for producing 2-cyanobiphenyls represented by the formula (I), which comprises dehydrogenating and decarboxylating cyano-2-carboxytetrahydrobiphenyls.

[0008]

[Chemical formula 3]

[0009]

[Chemical formula 4]

The 2-cyano-2-carboxytetrahydrobiphenyls of the formula (IV) are represented by the formula (III) by cycloaddition reaction of α-cyanocinnamic acid esters of the formula (II) with butadiene. It is produced by producing 2-cyano-2-alkoxycarbonyltetrahydrobiphenyls and then subjecting them to further hydrolysis reaction.

[0011]

[Chemical formula 5]

[0012]

[Chemical formula 6]

The 2-cyanobiphenyls of the present invention can be produced by the method of producing 2-cyano-2-carboxytetrahydrobiphenyls of the formula (IV) by the above-mentioned method, followed by dehydrogenation and decarboxylation. Particularly preferred.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The α-cyanocinnamic acid esters of the formula (II) used in the present invention are obtained by dehydration condensation of benzaldehydes represented by the following formula (VI) and cyanoacetic acid esters represented by the following formula (VII).

[0020]

[Chemical formula 7]

[0021]

[Chemical formula 8]

Specific examples of benzaldehydes include benzaldehyde, p-tolualdehyde, m-tolualdehyde, p-ethylbenzaldehyde, p-anisaldehyde and the like. The cyanoacetic acid ester is preferably methyl or ethyl ester.

For the reaction of benzaldehydes with cyanoacetic acid ester, a reaction widely known as a condensation reaction of active methylene compounds (for example, Org. React., Vol15., P.204.) Is applied, and a known catalyst or reaction is applied. It can be performed by adopting conditions. However, a secondary amine such as piperidine, morpholine, or dibutylamine is desirable as a catalyst for synthesizing in a particularly high yield. The amount used is 0.5 to 50 mol%, preferably 2 to 30 mol% based on the benzaldehyde used.

The amount of cyanoacetic acid ester used is 0.9 to 2 mol, preferably 1.0 to 1. per mol of benzaldehyde.
It is 5 mol. The reaction temperature is usually room temperature to 180 ° C, preferably 50 to 150 ° C. Hydrocarbons, halogenated hydrocarbons, alcohols and the like can be used as the solvent, but the boiling point thereof is within the range of the above reaction temperature at around normal pressure, and the produced water can be removed azeotropically from the reaction system. Solvents such as benzene or toluene are preferred. The amount of the solvent used is 200 to 4000 ml, preferably 300 to 2000 ml, based on 1 mol of the aldehyde used. The reaction time is 0.1 to 15 hours, preferably 0.5 to 8 hours. The resulting α-cyanocinnamic acid esters are easily separated and purified by distillation or recrystallization using a hydrocarbon or alcohol solvent.

Next, the 2- of the above formula (III) is formed by a cycloaddition reaction between α-cyanocinnamic acid esters and butadiene.
A method for producing cyano-2-alkoxycarbonyltetrahydrobiphenyls will be described.

The amount of butadiene used is from 1 to 10 mol, preferably 2 to 1 mol of α-cyanocinnamic acid esters.
~ 5 mol. Note that, instead of butadiene, it is within the scope of the present application to use a butadiene equivalent such as 3-sulfolene which produces butadiene in the reaction.

The reaction is carried out in a pressure vessel at a temperature of 120 to 250 ° C., preferably 150 to 200 ° C. for 1 to 15 hours, preferably
Do 2 to 8 hours. Hydrocarbons, halogenated hydrocarbons, alcohols and the like can be used as the solvent, but they are not particularly required. From the viewpoint of yield, it is preferable to carry out without solvent.

Next, the 2-cyano-2-carboxytetrahydrobiphenyls of the formula (IV) can be obtained by further hydrolyzing the 2-cyano-2-alkoxycarbonyltetrahydrobiphenyls thus obtained. At this time, it is not necessary to separate and purify the 2-cyano-2-alkoxycarbonyltetrahydrobiphenyls.

The hydrolysis can be carried out with either acid or alkali, but the cyano group is also hydrolyzable, so it can be carried out at a lower temperature, and the alkoxycarbonyl group can be hydrolyzed quickly, such as sodium hydroxide or potassium hydroxide. Is preferably used. The amount used is 1 to 4 with respect to 2-cyano-2-alkoxycarbonyltetrahydrobiphenyl.
It is an equivalent, preferably 1.1 to 2 equivalents. As the solvent, an alcohol solvent such as methanol, ethanol or ethylene glycol or a hydrocarbon solvent such as benzene or toluene can be used. In the case of an alcohol type, since the solubility of the alkaline component is increased, water may be contained within a range not inhibiting the reaction. In the case of a hydrocarbon solvent, the reaction is carried out in a two-phase system with an alkaline aqueous solution. At this time, the concentration of the alkaline aqueous solution is preferably 10 to 60 wt%. Further, a mixed solvent of an alcohol solvent and a hydrocarbon solvent may be used. The amount used is 200 to 4000 ml, preferably 400 to 2 mol, per 1 mol of 2-cyano-2-alkoxycarbonyltetrahydrobiphenyls.
It is 2000 ml. The reaction temperature is 0 to 180 ° C, preferably room temperature to 100 ° C. Below this temperature the reaction is slow,
When it is high, the amount of side reactions increases. The reaction time is 0.5 to 15 hours, preferably 1 to 8 hours. After the reaction, 2-cyano-2-carboxytetrahydrobiphenyls can be obtained by neutralizing the reaction solution with hydrochloric acid or the like. Purification can be performed by recrystallization using a hydrocarbon solvent or alcohol solvent.

Next, a process for producing 2-cyanobiphenyls by dehydrogenation and decarboxylation using 2-cyano-2-carboxytetrahydrobiphenyls as a raw material will be described.

2-Cyano-2-carboxytetrahydrobiphenyls are easily decarboxylated by heating. Since this decarboxylation proceeds very rapidly at the temperature during the dehydrogenation reaction described below, it is not necessary to carry out the decarboxylation reaction independently, and it is possible to perform it simultaneously with the dehydrogenation reaction. This is extremely advantageous.

The dehydrogenation reaction is carried out in the presence of a known appropriate dehydrogenation catalyst. The catalyst that can be preferably used is one containing at least one platinum group element consisting of platinum, palladium, osmium, iridium, ruthenium and rhodium as a catalyst component, and particularly preferably at least one of palladium and platinum. It is a waste. These platinum group elements can be used alone or as salts such as chlorides, acetates, nitrates and the like. When used as a salt, it is preferably calcined by a conventional method before use.

These catalyst components may also be used in any suitable carrier such as activated carbon, graphite, silica, alumina, silica.
-It may be in the form of being supported on alumina, zeolite, titania, magnesia, zirconia, diatomaceous earth, barium sulfate or the like. The method for preparing these catalysts is not particularly limited, and they can be prepared by a known method such as an impregnation method or an ion exchange method.

The dehydrogenation reaction may be carried out in either a flow system or a batch system. Reaction temperature is 100-350
C., preferably 150 to 300.degree. From the viewpoint of reaction rate, it is advantageous that the reaction temperature is high, but if it is higher than the above range, it is not preferable because of problems such as side reaction and decomposition reaction. Although the dehydrogenation reaction can be performed under pressure, the reaction under pressure is not a good idea from the point of equilibrium.

In the case of the batch system, the reaction can be carried out without solvent, but the reaction is carried out under reflux at normal pressure or under reduced pressure with a high-boiling point solvent because it is efficient in removing hydrogen generated outside the system. is there. Examples of such a solvent include cumene,
Examples thereof include cymene, diisopropylbenzene, decahydronaphthalenequinoline, benzonitrile, nitrobenzene, and diglyme, and these can also be used as a mixed solvent. In particular, the selectivity is improved when benzonitrile, nitrobenzene or a solvent containing these is used. The amount used is 100 to 5000 ml, preferably 300 to 3000 ml, per 1 mol of 2-cyano-2-carboxytetrahydrobiphenyls. The amount of catalyst used is 2-cyano
-2- 0.0001 to 1, preferably 0.001 to 0.5 in terms of molar ratio of platinum group element to carboxytetrahydrobiphenyls
Is the range. The reaction time is 0.5 to 50 hours, preferably 1
~ 24 hours.

On the other hand, in the case of the flow system, it can be carried out by supplying a solution of 2-cyano-2-carboxytetrahydrobiphenyls into a reaction tube filled with the above catalyst. As the solvent that can be used, in addition to the solvent that can be used in the batch system, preferred solvents include benzene, toluene, and xylene. The supply rate is 0.1 to 200 mol per hour, which is the amount of 2-cyano-2-carboxytetrahydrobenzene per 1 mol of the platinum group element of the catalyst component,
It is preferably 1 to 50 mol, and the amount of catalyst and the flow rate are set so that such conditions are satisfied.

Further, in the present invention, it is preferable to carry out the dehydrogenation reaction in the presence of oxygen in order to improve the selectivity. This is because oxygen combines with hydrogen generated by the dehydrogenation reaction to form water, which has an effect of suppressing by-products caused by hydrogen.
Oxygen may be used as pure oxygen, may be air, or may be diluted with another inert gas such as helium, argon, nitrogen or carbon dioxide. The amount used is 2-cyano-2-carboxytetrahydrobenzene
It is 0.05 to 10 mol, preferably 0.2 to 3 mol per 1 mol. If it is less than this range, the substantial effect is small,
When the amount is large, side reactions due to oxygen may be a problem. The supply of oxygen or diluted oxygen can be carried out by blowing it into the reaction solution for a predetermined reaction time in the case of the batch system, and by carrying it with the supply solution in the case of the flow system.

[0038]

EXAMPLES The present invention will be described more concretely with reference to the following examples. [Example 1] Condensation reaction step (Production example of α-cyanocinnamic acid esters of formula (II)): p-tolualdehyde 120.15 g ( 1mol), ethyl cyanoacetate 115.40g (1.02m
ol), 8.72 g (0.1 mol) of morpholine and 500 ml of toluene, and heat to reflux in an oil bath. With the start of reflux, the produced water flows out together with toluene and starts to accumulate in the dehydrated trap. After 2 hours, the flask was allowed to cool and a part of the reaction solution was taken out and analyzed by gas chromatography.The conversion rate of p-tolualdehyde was 99%, and the selectivity was 98%, 4-methyl-α-
Ethyl cyanocinnamate had formed. The water in the dehydration trap was about 18 ml. The reaction solution was washed twice with 300 ml of water and then concentrated, and the residue was recrystallized from isopropanol to obtain 193.73 g of ethyl 4-methyl-α-cyanocinnamate. The yield was 90% based on p-tolualdehyde.

[Examples 2 and 3 and Comparative Examples 1 to 4]
The same reaction as in 1 was carried out by replacing morpholine with the same amount of another catalyst. The reaction conditions and the like are the same as in Example 1. The results are shown in Table 1. The conversion and selectivity are based on p-tolualdehyde and are the analytical values after 2 hours obtained by gas chromatography.

[0040]

[Table 1]

[Examples 4 to 6] The same reaction as in Example 1 was carried out using the same amount of other benzaldehydes. The results are shown in Table 2. The conversion rate and the selectivity are the values analyzed by gas chromatography based on the benzaldehydes used.

[0042]

[Table 2]

Example 7 Cycloaddition reaction step (formula (II
Synthesis of 2-cyano-2-alkoxycarbonyltetrahydrobiphenyls of I)): 4-methyl-obtained in Example 1
50.00 g (0.232 mol) of ethyl α-cyanocinnamate was charged into a 300 ml autoclave, and 60 g of butadiene (1.1 mol) was added to this.
l) was press-fitted. After heating to 200 ° C. and stirring for 3 hours, the mixture was allowed to cool, 100 ml of toluene was added to form a solution, and the mixture was taken out. When analyzed by gas chromatography, 4-methyl-
The conversion of ethyl α-cyanocinnamate is 98% and the selectivity is 99%.
2-Cyano-2-ethoxycarbonyl-4′-methyltetrahydrobiphenyl was produced in an amount of%.

[Examples 8 to 11] The same reaction as in Example 7 was carried out by changing the amount of butadiene, the reaction temperature and the reaction time. The results are shown in Table 3. Conversion and selectivity are 4-methyl-
It is a value analyzed by gas chromatography based on α-ethyl cyanocinnamate.

[0045]

[Table 3]

[Example 12] Hydrolysis reaction step (formula (I
V) Synthesis of 2-cyano-2-carboxytetrahydrobiphenyls): The total amount of the toluene solution of the reaction solution obtained in Example 7 was transferred to a 500 ml three-necked flask, and
40 g of a 30 wt% sodium hydroxide aqueous solution was added, and the mixture was vigorously stirred at room temperature for 2 hours. After this, 100 ml of toluene and 10%
120 ml of a hydrochloric acid aqueous solution was added for neutralization, and the mixture was allowed to stand and then separated. Further, the toluene phase was washed twice with 100 ml of water. Toluene
100 ml of the solvent was distilled off, and crystals were deposited on standing, so this was filtered and dried to obtain 47.64 g of 2-cyano-2-carboxy-4'-methyltetrahydrobiphenyl. Yield is 4-methyl-α
-85% based on ethyl cyanocinnamate. Got 2
Physical properties of -cyano-2-carboxy-4'-methyltetrahydrobiphenyl were as follows. ¹ H-NMR (CDCl ₃ , δ (based on tetramethylsilane)), ppm: 2.32 (3H, s), 2.6 to 2.9 (4H, m), 3.23 (1
H, dd, J = 7Hz, 12Hz), 5.7 ~ 6.0 (2H, m), 7.10 (2H, d, J = 8H
z), 7.26 (2H, d, J = 8Hz), 10.86 (1H, br.s) ¹³ C-NMR (CDCl ₃ , δ (tetramethylsilane standard)), ppm: 20.9, 30.0, 34.9, 44.5, 49.5 , 117.
2, 121.3, 127.6, 128.0, 129.4, 135.3, 137.8, 173.9 Melting point (under nitrogen): 93.1 ° C (decomposition / decarboxylation) Infrared absorption spectrum: Fig. 1

[Example 13] Decarboxylation / dehydrogenation step (synthesis of 2-cyanobiphenyls of the formula (I)): Powdery Pd in which 10% Pd is supported in a glass tubular reactor having an inner diameter of 12 mm / 0.21 g of activated carbon catalyst was charged and heated to 200 ° C. Example 11
A solution of 2.41 g of 2-cyano-2-carboxy-4'-methyltetramethylbiphenyl obtained in 1. in 80 ml of xylene was continuously introduced from the top of this reactor at a flow rate of 8 ml / hour. At this time, nitrogen was introduced at a flow rate of 100 ml / min and air was introduced at a flow rate of 1 ml / min at the same time. The reaction product was collected by a trap attached at the bottom of the reaction tube. When the reaction mixture was analyzed by gas chromatography, 2-cyano-4′-methylbiphenyl was produced in a yield of 78% (1.51 g). (Yield is 2-cyano
-2-Carboxy-4'-methyltetrahydrobiphenyl standard, synonymous with Examples 14-19 below. )

[Examples 14 to 16] The same reaction as in Example 13 was carried out without changing the kind of catalyst, the amount of catalyst and the reaction temperature. Other conditions are the same as in Example 13. The results are shown in Table 4. The yield is the value analyzed by gas chromatography.

[0049]

[Table 4]

[Example 18] Pd / activated carbon catalyst in pellet form in which 2% Pd was loaded in a tubular reactor made of glass having an inner diameter of 24 mm
11.81 g was charged and heated to 220 ° C. A solution of 28.95 g of 2-cyano-2-carboxy-4'-methyltetrahydrobiphenyl in 1200 ml of xylene was added 50 m from the top of this reactor.
It was introduced continuously at a flow rate of l / h. At this time, nitrogen
250 ml / min, air was introduced at a flow rate of 5 ml / min. The reaction product was collected by a trap attached at the bottom of the reaction tube. When the reaction mixture was analyzed by gas chromatography,
The yield of 2-cyano-4'-methylbiphenyl was 80%.
After xylene was distilled off from this reaction mixture, the residue was distilled to give 20.60 g of crude 2-cyano-4'-methylbiphenyl having a boiling point of 140 to 15
Obtained as a 2 ° C. fraction. This fraction was recrystallized twice from n-hexane to obtain 13.91 g of 2-cyano-4'-methylbiphenyl. The yield was 60%, and the purity was 99.5% as analyzed by liquid chromatography.

Example 19 2-Cyano-2-carboxy-4'-methyltetrahydrobiphenyl obtained in Example 12
48 g (2.0 mmol), 3 ml of benzonitrile and 10% Pd supported
0.040 g of Pd / activated carbon catalyst was charged into a three-necked flask having an internal volume of 20 ml equipped with a condenser, and heated and refluxed for 8 hours. After the reaction, the yield was 72% when analyzed by gas chromatography.
2-cyano-4'-methylbiphenyl was produced at

[0052]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide an industrial method for selectively producing 2-cyanobiphenyls using inexpensive raw materials and free from problems such as waste.

[Brief description of drawings]

1 is the 2-cyano-2-carboxy obtained in Example 12.
3 is an infrared absorption spectrum of -4'-methyltetrahydrobiphenyl.

Continuation of front page (56) References JP-A-2-3653 (JP, A) JP-A 64-79137 (JP, A) JP-A 9-59240 (JP, A) J. Org. Chem. , Vol. 59, No. 25 (1994) p. 7774-p. 7778 Tetrahedron: Asym METRY, Vol. 6, No. 6 (June 1995) p. 1409-p. 1418 (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 253/30 C07C 255/50 C07C 255/54

Claims (5)

(57) [Claims] 1. A 2-cyano-2-carboxytetrahydrobiphenyl compound represented by the formula (IV) is simultaneously dehydrogenated and decarboxylated.
-Method for producing cyanobiphenyls. [Chemical 1] [Chemical 2] 2. The method for producing 2-cyanobiphenyls according to claim 1, wherein the dehydrogenation reaction is carried out in the presence of a catalyst containing at least one platinum group element. 3. The method for producing 2-cyanobiphenyls according to claim 2, wherein the at least one platinum group element is palladium or platinum. 4. The method for producing 2-cyanobiphenyls according to claim 2 or 3, wherein the dehydrogenation reaction and the decarboxylation reaction are carried out at a reaction temperature of 100 to 350 ° C. 5. The method for producing 2-cyanobiphenyls according to claim 2, wherein the dehydrogenation reaction is carried out in the presence of oxygen.