JPH0262837A - Production of aromatic carbinol - Google Patents

Abstract

PURPOSE:To produce an aromatic carbinol useful as a raw material for drugs and agricultural chemicals with a few side reactions industrially and advantageously without requiring a specific device by using an organic amine as a promoter and hydrogenating an aromatic ketone in the presence of a palladium catalyst. CONSTITUTION:An aromatic ketone (e. g., p-isobutylacetophenone) shown by the formula (R' is H, 1-5C alkyl, 1-2C alkoxy or halogen, R'' is alkyl or arylalkyl) is hydrogenated in the presence of a palladium catalyst supported on a carrier to give an aromatic carbinol [e. g., (p-isobutylphenyl) methylcarbinol]. In the reaction, 0.4-0.6 pt.wt. based on 1 pt.wt. palladium supporting catalyst of an organic amine, especially pyridine or triethylamine is present as a promoter. The method has no problems such as precipitation of alkali hydroxide and alkaline metallic salt and purification is readily carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for hydrogenating aromatic ketones. In particular, the present invention relates to a method for hydrogenating aromatic ketones to produce aromatic carbinol.

Aromatic carbinol produced by the method of the present invention is a compound mainly used as a raw material for medicines and agricultural chemicals.

[Prior art and problems to be solved by the invention] In the production of carbinol by the hydrogenation reaction of aromatic ketones, unlike the case of hydrogenation of aliphatic ketones, not only the carbonyl group but also the aromatic ring participates in the reaction. Furthermore, since the carbyl/-hydrogenated product has a benzyl alcohol type hydroxyl group, the hydroxyl group is easily subjected to subsequent hydrogenolysis, which complicates the reaction. Therefore, it is common practice to try to obtain the desired product by selecting an appropriate catalyst and reaction conditions. For example, it is well known that the reaction rate can be improved by adding an alkali to the Raney-Ninkel catalyst [Kusabuki et al., Pharmaceutical Research.

Volume 30, 26H, 1952]].

The effect of this alkaline additive is not only to improve the reaction rate, but also to suppress the hydrogenolysis of benzyl alcohol-type hydroxyl groups. has been reported to be quantitatively produced [Yoken Fine Chemical ■Technical Report [Hydrogenation Reaction Using Raney Catalyst J Pd2 (1980)]. As additives for this alkali, in addition to alkali metal salts of organic acids such as the aforementioned acetate, alkali metal hydroxides (e.g., I-'I-um hydroxide, potassium hydroxide) can be used. [New Experimental Chemistry Course Volume 15 Oxidation and Reduction]
n) P408'l.

In addition, in reactions using Raney nickel catalysts, usually 1
00kg/cn+2.00kg/cn+2.1.00℃ or higher, which requires operation under high temperature and high pressure conditions, which is not desirable in terms of equipment costs in industrial scale production, whereas similar effects can be achieved at relatively low temperatures and low pressures. A palladium catalyst supported on activated carbon has been reported as a catalyst for obtaining this [Journal of Organic Chemistry (JOC), 24]
Vol., P1855 (1959)).

The present inventor carried out the operation shown in the comparative example described below and confirmed that in the presence of an alkaline additive, the same effect as Raney nickel can be obtained with a palladium catalyst supported on activated carbon.

However, since alkali metal hydroxides or alkali metal salts of organic acids have very low solubility in aromatic ketones, a solvent such as methanol or ethanol is required. Furthermore, when the solvent is separated and recovered in the post-isolation and purification process of the product, the aromatic carbinol remaining in the bottom liquid is hydroxylated). Salt will precipitate. This is because alkali metal hydroxides such as sodium hydroxide or alkali metal salts of organic acids have only a small solubility in aromatic carbinol. This causes problems such as clogging of perforated plates during the carbinol rectification process and fouling of the reboiler itself. Therefore, in order to remove this precipitate, operations such as filtration and decantation are performed, but in production on an industrial scale, the process becomes complicated and is not preferable.

An object of the present invention is to solve the problem of precipitation of alkali hydroxides and alkali metal salts when producing aromatic carbinol from aromatic ketones using a palladium-supported catalyst.

[Means to solve the problem]

In place of an alkali metal hydroxide or an alkali metal salt of an organic acid, the present inventors used an organic amine with high solubility in both aromatic ketones and aromatic carbinols, preferably pyridine or triethylamine, as a cocatalyst. It was discovered that when added as a palladium catalyst and used in combination with a palladium catalyst supported on activated carbon, the hydrogenation of aromatic ketones proceeds rapidly with few side reactions such as hydrogenolysis of aromatic carbinol, and the present invention was completed. Ta.

That is, the present invention provides an aromatic carbinol characterized in that an organic amine is used as a promoter when producing an aromatic carbinol by hydrogenating an aromatic ketone in the presence of a palladium catalyst supported on a carrier. This is a manufacturing method.

The present invention will be described in detail below, including implementation conditions.

The organic amine serving as a co-catalyst used in the present invention may be any one belonging to organic amines. Specific examples include ammonia, pyridine, piperidine, monomethylamine, dimethylamine, trimethylamine,
Amines such as monoethylamine, diethylamine, triethylamine, 1,8-diazabicyclo[:5.4.0E undecene 7, etc.] are used. These amines added as cocatalysts are all liquid substances at room temperature and do not cause any precipitation problem. Among them, pyridine and triethylamine are preferred.

The aromatic ketone used in the present invention has the following general formula (1)
This is shown in .

(In the formula, R' represents H or a C1-C5 linear or branched alkyl group, a C1-C2 lower alkoxy group, or a halogen, and R'' represents an alkyl group or an arylalkyl group.) Examples include acetophenone, propiophenone, n-propylphenyl ketone, 1-propylphenyl ketone, n-butylphenyl ketone, 1-butylphenyl ketone, sec-butylphenyl ketone, t-butylphenyl ketone, benzylphenyl ketone. , halogen-substituted phenylmethylketone, etc.

In the reaction of the present invention, a solvent may or may not be used, but when used, compounds that react with hydrogen in the presence of the palladium catalyst used in the present invention, such as olefins, acetylenes, etc. It is inappropriate to use , nitro compounds, etc. as a solvent because the hydrogenation efficiency of aromatic ketones becomes poor. For example, water, methanol,
It is preferable to use alcohols such as n-7'-propanol, n-butanol, 1-butanol, 5ec-butanol, and t-butanol in an amount of 0.6 parts by weight or less per 1 part by weight of the aromatic ketone. The use of the above solvents is not preferable because it increases both recovery energy and recovery time, and above all, it reduces production capacity.

The catalyst used in the present invention has palladium supported on a carrier. Activated carbon, silica gel, alumina, diatomaceous earth, pumice, etc. are used as carriers.
Any commercially available material may be used as long as it is supported in an amount of 0.1 to 20% by weight. The concentration of the palladium catalyst used is 0.1 to 1% by weight, preferably 0.25 to 0.5% by weight of the metal based on the aromatic ketone. 0.1
If the amount is less than 1% by weight, the reaction rate will be low;
When a larger amount of catalyst is used, the hydrogenolysis reaction of the aromatic carbinol produced tends to occur as a side effect.

The co-catalyst consisting of an organic amine, which is a feature of the present invention, is generally 0.2 to 0.8 parts by weight per 1 part by weight of the palladium-supported catalyst.
It is used in a range of parts by weight, preferably in a range of 0.4 to 0.6 parts by weight. If the amount is less than 0.2 parts by weight, the promoter effect will not be sufficient and the reaction rate will be low. On the other hand, if it exceeds 0.8 parts by weight, the life of the catalyst may be shortened.

The hydrogenation reaction can be carried out at a temperature in the range of 10°C to 200°C, but preferably 50°C to 150°C. Generally, if the temperature is below 50°C, the time required for the reaction will be longer, whereas if the temperature exceeds 150°C, side reactions of aromatic ketones, such as hydrogenation of aromatic rings and hydrogenolysis of aromatic carbinol, will more easily occur.

The hydrogenation pressure may be in the range of normal pressure to 150 kg/cm2, more preferably about 2 to 20 kg/cm2.

At low pressures, the reaction rate is slow, at high pressures there is a risk of side reactions, and above all, production equipment that can withstand high pressures is required.

The resulting reaction crude liquid is subjected to a rectification process after the palladium-supported catalyst is separated and removed by filtration.

If a solvent is used, a solvent recovery step is required prior to rectification of the product aromatic carbinol. Both this step and the rectification step can be carried out without any problem by using a general distillation apparatus.

Therefore, the present invention does not require any special equipment and can be easily carried out using conventional general reaction and purification equipment.

〔Example〕

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples for detailed explanation of the present invention.

Example-1 1! In an autoclave equipped with a magnetic stirrer, 130 g of p-inbutylacetophenone and 65.0 g of methanol were added.
) Add 6.5 g of ethylamine and 13.0 g of a catalyst made of 5% by weight of palladium supported on activated carbon, and
KG of H2 was charged and stirred at 60°C for 1 hour until gas absorption stopped. After that, the residual H2 in the autoclave was depressurized, and the palladium catalyst in the reaction crude liquid was removed by suction filtration.The liquid was quantitatively determined by gas chromatography, and the conversion rate of (p-inbutylphenyl)methyl carbinol was 97%. , was found to be produced with 100% selectivity. Further, from this reaction filtrate, methanonepetriethylamine was distilled off at normal pressure using a rotary evaporator to obtain 126.4 g of a concentrated solution. When this concentrated solution was analyzed by gas chromatography, it was found that it contained almost 100% (p-inbutylphenyl).
It turned out to be methyl carbinol.

Example 2 The same operation as in Example 1 was carried out, and the catalyst removed by suction filtration was charged again into the autoclave, and 130.0 g of p-inbutylacetophenone and 65.0 g of methanol were added. '
6.5 g of triethylamine were added, and 8 kg of H2 was charged to carry out a reaction. When this operation was repeated three times, (p-isobutylphenyl)methylcarbinol was converted at a conversion rate of 97% and 10% in all reactions.
Gas chromatography confirmed that it was produced with a selectivity of 0%.

Comparative Example-1 As in Example-1, 130 g of p-isobutylacetophenone was placed in a 1β autoclave equipped with a magnetic stirrer.
65.0 g of methanol and 13.0 g of a catalyst in which 5% by weight of palladium was supported on activated carbon were added, 8 KG of H2 was charged, and the mixture was stirred for 3 hours at 60° C. until gas absorption stopped. After the reaction was completed, the palladium catalyst in the crude reaction solution was removed by suction filtration, and the solution was quantified by gas chromatography, and it was found that (p-isobutylphenyl)
Methyl carbinol is 0.29 mo1%, p-isobutylethylbenzene is 95. The selectivity of (p-inbutylphenyl)methylcarbinol was 0.3%.

Comparative Example-2 In the same manner as Comparative Example-1, 130 g of p-isobutylacetophenone,
Methanol 65.0 g, sodium hydroxide 1.6 g
, Catalyst 13 with 5% by weight of palladium supported on activated carbon
．． 0 g was added, 8 KG of H2 was charged, and stirring was performed at 60° C. until gas absorption stopped, which required a rate of 3 hours. After the reaction was completed, the palladium catalyst in the reaction crude liquid was removed by absorption filtration, and the liquid was quantitatively determined by gas chromatography, and it was found that (p-isobutylphenyl)
It was found that methyl carbinol was produced with a conversion rate of 97% and a selectivity of 99%. However, when methanol was distilled off from this reaction filtrate at normal pressure using a rotary evaporator, sodium hydroxide precipitated.

〔Effect of the invention〕

As is clear from the above examples, instead of an alkali metal hydroxide or an alkali metal salt of an organic acid, pyridine or triethylamine, which is highly soluble in both aromatic ketones and aromatic carbinols, is used as a promoter.・By the method of the present invention, which is added in combination with a palladium catalyst supported on activated carbon, aromatic carbinol can be rapidly and with a selectivity of 100% from an aromatic ketone represented by formula (1). Can be manufactured with simpler equipment than conventional methods.

Claims (1)

[Scope of Claims] 1. An aromatic ketone characterized in that an organic amine is used as a cocatalyst when producing an aromatic carbinol by hydrogenating an aromatic ketone in the presence of a palladium catalyst supported on a carrier. Method for producing carbinol. 2. The method according to claim 1, wherein the aromatic ketone is an aromatic ketone represented by the following formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) (In the formula, R' represents H or a linear or branched alkyl group of C_1 to C_5, a lower alkoxy group of C_1 to C_2, or a halogen, and R" is an alkyl group. or an arylalkyl group.) 3. The method according to claim 1 or 2, wherein the organic amine is pyridine or triethylamine.