JPH06172238A - Production of tetrahydrobenzyl alcohol or vinylyslohexene - Google Patents

Abstract

PURPOSE:To obtain a method for producing tetrahydrobenzyl alcohol or vinylcyclohexene with minimized amount of by-produced butadiene polymer to a loss of a raw material. CONSTITUTION:This method for producing tetrahydrobenzyl alcohol or vinylcyclohexane comprises effecting the reaction in the coexistence of a metallic alkoxide in an amount of <1.0% based on the starting raw material under >=5kg/cm<2> pressure in synthesizing the tetrahydrobenzyl alcohol by the Diels- Alder reaction of butadiene with allyl alcohol or the vinylcyclohexene by the Diels-Alder reaction of the butadiene.

Description

Detailed Description of the Invention

[0001]

The present invention relates to tetrahydrobenzyl alcohol (hereinafter referred to as T) which is useful as an intermediate raw material for synthetic resins and the like.
HBA) or vinyl cyclohexene.

[0002]

2. Description of the Related Art As a method for producing THBA, a method of selectively hydrogenating an aldehyde group of tetrahydrobenzaldehyde obtained by a Diels-Alder reaction of butadiene and acrolein has been known (for example, Chem. Ber. 98) .
(6), 1928 (1965), JP-A-63-275538, etc.).

However, in carrying out the above method industrially, since acrolein is an extremely unstable and toxic compound, there are restrictions on its use and transportation on an industrial scale, and only aldehyde groups are hydrogenated. In order to leave the carbon double bond as it is, a high activity catalyst such as Raney nickel or platinum group, which is usually used for hydrogenation, cannot be used, and high pressure high temperature hydrogenation with a copper chromite catalyst or a stoichiometric amount of isopropyl alcohol is used. There is a problem in that there is no choice but to use a method that is industrially disadvantageous, such as the consumption of mail wine and Pondorf reduction.

[0004]

The above problems can be solved if THBA can be produced in a one-step reaction by the Diels-Alder reaction with butadiene using allyl alcohol instead of acrolein as a raw material. According to the known literature (US Pat. No. 2,557,136), the reactivity of allyl alcohol is lower than that of acrolein, so that THBA can be obtained only in a low yield.

In order to solve the problems of the prior art, the present inventors firstly make it effective as a catalyst in the Diels-Alder reaction (for example, "New Experimental Chemistry Course", Vol. 14, Synthesis of Organic Compounds). Reaction [I] p. 21
0) The use of a Lewis acid such as AlCl ₃ or BF ₃ was examined, but it had no effect (Comparative Examples 2 and 3 below), and surprisingly, a metal alkoxide such as tetrabutoxytitanium having a very weak effect as a Lewis acid is good. It has been found that it exhibits various catalytic activities.

Further, the use of this catalyst reduces the by-product of the butadiene polymer, which is a loss of the raw material, and is useful as an intermediate raw material for synthetic resins and the like, similar to THBA.
It was also found that the yield of vinylcyclohexene (hereinafter referred to as VCH), which is a Diels-Alder adduct of the molecule, is increased.

Further, as a result of further efforts by the present inventors to improve the THBA yield, the gas phase pressure during the reaction was 5 kg / cm ²
It was found that the yield of THBA can be further improved by increasing the above, and the present invention has been completed.

[0008]

Means for Solving the Problems That is, according to the present invention, "when synthesizing tetrahydrobenzyl alcohol by a Diels-Alder reaction of butadiene and allyl alcohol,
Alternatively, when synthesizing vinylcyclohexene by the Diels-Alder reaction of butadiene, 1.0
% In the presence of a metal alkoxide in the presence of a pressure of 5 kg / cm ² or more, and a method for producing tetrahydrobenzyl alcohol or vinylcyclohexene ”.

The present invention will be described in detail below. Butadiene and allyl alcohol are used as raw materials in the reactions that constitute the present invention.

Regarding the molar ratio of the raw materials charged, it is preferable to use allyl alcohol in excess of the stoichiometric ratio. Specifically, the molar ratio of allyl alcohol / butadiene is 1 to 10, more preferably 2 to 10. About 4 is advantageous.

When the allyl alcohol / butadiene molar ratio is less than 1, the loss due to the polymerization of butadiene increases,
It is not preferable because the yield is reduced.

On the contrary, when the molar ratio exceeds 10, it is not preferable in terms of yield and recovery of unreacted allyl alcohol.

The reaction may be carried out without a solvent, or using a solvent such as benzene or hexane is effective in suppressing side reactions such as polymerization. One of the features of the present invention is to use a metal alkoxide as a catalyst.

Specific examples of the metal alkoxide include titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetrabutoxide and other titanium alkoxides, aluminum trimethoxide, aluminum triethoxide, aluminum tripropoxide, aluminum. Aluminum alkoxides such as tributoxide are common, but titanium alkoxides give preferable results. It is essential that the catalyst concentration is less than 1.0% with respect to the starting material, but it is preferably 0.05 to 0.5% by weight.

If the catalyst concentration is less than 0.05% with respect to the starting material, the reaction rate will decrease, which is industrially disadvantageous. Conversely, if the catalyst concentration exceeds 1.0% with respect to the starting material, polymerization, etc. will occur. This is not preferable because it causes a decrease in yield due to the side reaction of.

The temperature at which the reaction is carried out is selected from the range of 50 ° C to 350 ° C, more preferably 100 ° C to 250 ° C.

When the reaction temperature is lower than 50 ° C., the reaction rate is lowered, which is industrially disadvantageous. On the contrary, when the reaction temperature is higher than 350 ° C., the yield is lowered due to polymerization of raw materials, decomposition of products and catalysts, etc. Not preferable.

In the present invention, it is essential to increase the reaction pressure to a pressure not lower than the vapor pressure of the raw materials butadiene and allyl alcohol itself, specifically to 5 kg / cm ² or higher, but the upper limit of the pressure is It is about 100 kg / cm ² .

Even if the reaction pressure is 100 kg / cm ² or more, the effect is not so improved.

When the reaction pressure is less than 5 kg / cm ² , the effect of pressurization is hardly seen, and pressurization is meaningless.

As a means of increasing the pressure during the reaction, a method of introducing an inert gas such as nitrogen or argon into the reaction system is generally used.

It is also effective to add a known polymerization inhibitor such as hydroquinone or phenothiazine in order to reduce the loss due to the polymerization of the raw materials, but it is not always an essential condition.

[0023]

The present invention will be described in more detail with reference to the following examples.

Example 1 Allyl alcohol 1 as a raw material was placed in a stainless steel autoclave having a capacity of 500 ml.
After enclosing 08.3 g, butadiene 28.0 g and titanium tetrabutoxide 0.14 g as a catalyst, 20
The temperature was raised to 0 ° C. and kept as it was for 8 hours. After cooling, the composition of the contents was analyzed by gas chromatography. The results are shown in Table 1.

(Example 2) Nitrogen gas 20 kg / cm ² (at room temperature, gauge pressure) was pressed in together with the raw material and the catalyst.
The reaction was carried out according to Example 1. The results are shown in Table 1.

(Example 3) Nitrogen gas 20 k with raw materials
g / cm ² (at room temperature, gauge pressure) was pressed in, and the reaction was carried out without using a catalyst. The reaction procedure was in accordance with Example 1. The results are shown in Table 1.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that the catalyst was not used and the pressurization with nitrogen gas was not performed. The results are shown in Table 1.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that 0.14 g of aluminum trichloride was used as the catalyst. The results are shown in Table 1.

(Comparative Example 3) Boron trifluoride as a catalyst
The reaction was carried out according to Example 1 except that 0.30 g of an ether complex was used. The results are shown in Table 1.

[0030] Table 1 raw material charged amount butadiene Total yield ^{(%) * A B C D} E F G Example 1 108.3 28.0 TTB ^** (0.14) None 87.4 30.8 36.4 Example 2 109.3 28.5 TTB (0.14) 20 95.6 36.3 47.0 Example 3 112.3 29.0 None 20 97.6 32.0 46.4 Comparative Example 1 108.2 28.0 Without None 93.0 26.7 30.4 Comparative Example 2 108.7 28.5 AlCl ₃ (0.14) Without 49.5 17.8 20.4 Comparative Example 3 108.1 29.5 BF ₃ -Diethyl ether None 54.0 2.7 8.7 (0.30) The alphabetical designations in Table 1 indicate the following.

A: allyl alcohol (g) B: butadiene (g) C: catalyst (g) D: N ₂ pressure (kg / cm ² · gauge) E: butadiene conversion (%) F: tetrahydrobenzyl alcohol G: vinyl cyclohexene TTB: tetrabutoxy titanium

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Claims (1)

[Claims] 1. When synthesizing tetrahydrobenzyl alcohol by a Diels-Alder reaction of butadiene and allyl alcohol, or when synthesizing vinylcyclohexene by a Diels-Alder reaction of butadiene, in the presence of less than 1.0% of metal alkoxide relative to the starting material. A method for producing tetrahydrobenzyl alcohol or vinylcyclohexene, which comprises reacting at a pressure of 5 kg / cm ² or more.