DE2028348A1 - Process for the preparation of arylacatates - Google Patents

Description

MPP-50 ASAHI- _i ',

ASAHI KASBI KOGYO KABUSHIKI KAISHA
Osaka, Japan

"Process for the production of aryl acetates"

Priority:

June 9, 1969, Japan, No. 44644/69

June 9, 1969, No. 44645/69

November 5, 1969, No. 88113/69

November 17, 1969, No. 91409/69

4 ο February 1970, No. 9304/70

The invention relates to a process for the preparation of aryl acetates by reacting a benzene with acetic acid.

Aryl acetates can easily be hydrolyzed to the corresponding phenols and are moreover more stable to oxidation than the free phenols. The aryl acetates have different as starting compounds for preparing mono- ^K times compounds such as oxidation products of Tolylacetats, which is oxidized in the pendent methyl group, significance.

109851/1919

Belgian patent 696852 describes a one-step Process for the preparation of aryl acetates from benzenes using metallic palladium. A similar procedure, which works with palladium acetate is described in British patent specification 1167428. The Belgian patent specification 720733 and Dutch patent 6811842 describe improvements to this process, taking the reaction system bismuth or tellurium is added to increase the yield.

In the aforementioned processes, however, the palladium does not act as a catalyst. The yields of aryl acetates in example 6 of Belgian patent specification 696832, in example 1 of British patent specification 1167428 and in examples 1 to 10 of Dutch patent specification 6811842 do not exceed 100% , based on palladium. Also in the example in which the above-mentioned palladium compound is used according to the flow process, the yields of aryl acetates, based on palladium, are very low. In addition, it follows from Example 4 of British Patent 1167428 that when using palladium acetate alone from. substituted benzenes, such as toluene, no tolyl acetate (the acetoxy group is directly connected to the benzene nucleus), but benzyl acetate (the acetoxy group is in the side chain).

Ichikawa et al. (J. Ohem, Soc. Of Japan, 90, (No.2), p 212) describe a process for the acetoxylation of the benzene nucleus using palladium nitrate as a catalyst. l) ie Yield of aryl acetate, based on the palladium used, is

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but also carries, here under 100 fo. As in the aforementioned processes, the palladium does not act as a catalyst "; however, when toluene is used as the starting compound, tolyl acetate is obviously obtained.

If the palladium only acts as a reactant, it is necessary to remove the unreacted palladium after recovery and to feed regeneration back into the reaction system. The reuse of the expensive precious metal is inevitable because of Losses during regeneration are economically disadvantageous.

The object of the invention was therefore to overcome the aforementioned disadvantages and a more economical process for production of aryl acetates. This object is achieved by the invention solved.

The invention thus relates to a method for producing Aryl acetates, which is characterized in that one is a benzene of the general formula (I)

^ R ₂ (D

where R. and R. Brings alkali nitrate at temperatures of 30 to 300 ⁰ C to implement.

1 098 ^ 6 1/19 19

In the process of the invention, the aryl acetates are obtained in high yield. Ba the palladium "or the" palladium compound " acts as a catalyst, there is no need to recover and regenerate the palladium.

The process of the "invention" can be described by the reaction equation

+ AcOH +

represent, in which R. and R _{2 have} the aforementioned meaning and Ac represents an acetyl group.

Table I illustrates the technical part of the process according to the invention. All experiments in Table I are carried out in a 100 ml pressure vessel at 10O ⁰ C and an oxygen pressure of 30 kg / cm using 20 ml of benzene and 20 ml of acetic acid.

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- 5 - Table T

attempt
No.

Catalyst (amount)

Yield of aryl acetate, based on palladium (fo)

Response time (hours) 15 25

Pd (OAc) ₂ (0.2 g)

10

15th

₅₂ (0.2 g)

, Pd (OAc) ₂ (0.2 g)

- KWO.

Pd

(0.5 g)

Pd - SiO,

(0.2 g) (10 *

Pd (NO ₃ ) ₂ (0.2 g)

60

85

(0.2 g) (10 ml) 160

SiO,

ENT,

(0.2 g) (10 ml) (0.5 ml)

340

120

350

5-10

70

120

Traces traces

460

720

Table I shows that aryl acetates are formed even when palladium acetate or palladium nitrate is used alone. The yield of aryl acetates, based on palladium, is up to a maximum of 75 ψ, ie the palladium acts here as a reactant and not as a catalyst. In experiment 3, when potassium nitrate is also used, the yield of aryl acetate, based on palladium, is 120 io. This shows that the palladium is not consumed by a single reaction, but can re-enter the reaction. If the catalysts are applied to a support (see Experiments 4 and 5), if a small one is present

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Amount of nitrate ions in the system greatly increases the yield. In experiment 6, the yield, based on palladium, increases to 720 <fo . This clearly shows the catalytic effect of palladium.

Palladium)

Compounds suitable as catalysts for the process of the invention are e.g. oxides, hydroxides, acetates, propionates or nitrates. When using metallic palladium, one obtains this by reducing a

A connection
brought palladium 'with a reducing agent such as hydrogen, aqueous formaldehyde or hydrazine, and subsequent aftertreatment of the reduction product. Any desired palladium salts, for example the chlorides, can be used.

Alkali nitrates suitable for the process of the invention are e.g. Lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate or cesium nitrate.

The nitric acid or the alkali nitrate can either be added to the reaction system or added to the catalyst. In the first case, an amount of 0.2 to 0.001 mol, especially 0.1-0.002 moles, added per mole of acetic acid. If the nitric acid or the alkali nitrate is added to the catalyst, so the preferred amount is 15 to 0.01 mol, especially 10 to 0.03 mol, per gram atom of palladium.

In a particular embodiment of the process of the invention, alkali metal salts of aliphatic carboxylic acids, such as formates, acetates are used or propionates of lithium, sodium, potassium, rubidium or cesium, used as cocatalysts. The alkali salt will

109851/1919

generally in an atomic plant ψρη alkali:

5m. ". 3! Älladium

from 30: 1 to 0.1: 1, preferably 10: 1Ws "O ₁ SVi _i: vVrwend§tV; Däfe 'alkali ..1 ^ salts can either be added to the" catalyst "or separately to the reaction system If the procedure is as follows: a palladium salt applied to a support material is reduced, the alkali metal salt is only added after the reduction has ended. cal purposes common carrier file, such as Ak-; activated carbon, silicic acid, aluminum oxide or a mixture of silicic acid and aluminum oxide, applied, used *

Benzols of the general formula (I) which are suitable for the process of the invention are, for example, toluene, o-, m- or p-xylene, ethylbenzene, o-, m- or p-ethyltoluene, o-, m- or p-diethy! benzene, cumene or tert-butylbenzene.

The ratio of the benzene of the general formula (I) to acetic acid does not play a special role. As a carrier gas for oxygen inert gases such as nitrogen or carbon dioxide can be used.

The method of the invention is carried out at temperatures of 50 to 300 ⁰ C, preferably 50 to 250 ° C, under normal pressure or under elevated pressure either in liquid or in the gas phase.

The process can be carried out using a wide variety of methods, e.g. a Flow process, a liquid process with gas admixture under Ver-r vortex or a liquid process with blowing in gas. ·

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ORIGINAL INSPECTED

Specific examples of those produced by the process of the invention from a benzene of the general formula (I) and acetic acid Aryl acetates are:

Phenyl acetate from benzene, o- or p-tolyl acetate from toluene, 2,4-dimethylphenyl acetate from o-xylene, 2,6-, '2,4 · -' or 3,5-dimethylphenyl acetate from m-xylene, 2,5-dimethylphenyl acetate p-xylene, o- or p-ethylphenyl acetate from ethylbenzene, 3-methyl-4-ethylphenyl acetate from o-ethyltoluene, 2-tat or 2-ethyl-4-methylphenyl acetate from m-ethyltoluene, 2-methyl-5-ethylphenyl acetate or 2-ethyl-5-methylphenyl acetate from p-ethyltoluene, 3> 4-diethylphenyl acetate from o-diethylbenzene, 2,4- or 3,5-diethylphenyl acetate from m-diethylbenzene, 2,5-diethylphenyl acetate from p-diethylbenzene, p-isopropylphenyl acetate from cumene or p-tert-butylphenyl acetate from tert-butylbenzene.

The examples illustrate the invention.

Example 1

A 100 ml three-necked flask with thermometer, reflux condenser and gas inlet tube is charged with a mixture of 30 ml benzene, 10 ml acetic acid, 0.5 g palladium acetate and 2.0 g potassium nitrate. The temperature in the reaction vessel is kept at 8O ⁰ O and gaseous oxygen is passed with a flow. speed of 20 ml / min. After a reaction time of 20 hours, work-up is carried out in a known manner. Phenyl acetate is obtained in a yield of 130%, based on palladium (1.3 mol per gram atom of Pd), along with some biphenyl as a by-product.

Upon repetition of the above example by using 2.0 g of potassium acetate in place of 2.0 g of potassium nitrate are obtained

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after 20 hours of reaction only about 15 $ yield of phenyl acetate. *

Example 2

A solution of 0.1 g palladium nitrate and 0.5 g potassium nitrate

in dilute aqueous nitric acid is mixed with 10 ml of granulated silica gel and evaporated to dryness.

A 100 ml pressure vessel made of chrome steel (SUS-32) is charged with 10 ml of the aforementioned catalyst, 20 ml of benzene and 20 ml of acetic acid and then sealed. Then the pressure vessel is pressurized with oxygen up to a pressure of 40 atmospheres. The pressure vessel is then mounted on a shaking device and then placed in an oil bath of 100 ⁰ G for 16 hours. N _e this time, the yield of phenyl acetate and biphenyl 380 and 40 fo, based on the atomic quantity of palladium. This reaction mixture is subjected to another 10-hour reaction after the pressure vessel has been re-pressurized with oxygen up to a pressure of ^ 40 atm. The yields of phenyl acetate and bi-phenyl increase to 510 and 55 ^a / °, respectively.

Example 5

0.15 g of palladium acetate and 1.0 g of potassium nitrate are dissolved in dilute nitric acid and evaporated to dryness with 20 ml of granulated silica gel. This catalyst is placed in the pressure vessel from Example 2 together with 30 ml of toluene and 10 ml of acetic acid. Thereafter, the pressure vessel with oxygen up to a pressure of 55 atm and applied on a shaker mounted 16 hours in a Ölbd of 12O ⁰ O adjusted. The analysis shows the yields of p-tolyl acetate, o-tolyl-

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aoetat, benzyl acetate and nitrotoluene to 180 ,. 52, 32 or 16 $, based on palladium. The reaction mixture is then returned to the reaction vessel for another 10 hours Subjected to reaction under an oxygen pressure of 55 atm. Thereafter, the yields of p-tolyl acetate, o-tolyl acetate, Benzyl acetate and nitrotoluene 270, 81, 50 and 23 $, based on Palladium..

Example 4

Ό, 2 g of palladium hydroxide, 0.2 g of lithium nitrate and 0.5 g of potassium 'nitrate are dissolved in dilute aqueous nitric acid and evaporated to dryness with 10 ml of granulated activated charcoal. 10 ml of the catalyst prepared in this way are placed in a U-shaped reaction vessel made of hard glass (internal diameter .8 mm, length 20 cm). After the reaction vessel is set in an oil bath at 100 ⁰ C, a mixture of gaseous benzene, acetic acid, oxygen and nitrogen (volume ratio 5: 5ί2: 1Ο), introduced at a flow rate of 50 ml / min. After a reaction time of 10 hours, the reaction mixture is analyzed. 2.5 mol of phenyl acetate are obtained per gram atom of palladium.

Example 5

0.17 g of palladium chloride are dissolved in dilute hydrochloric acid and evaporated to dryness with 10 ml of granulated silica gel. That

alkaline reaction product is treated with hydrazine hydrate for reduction, carefully washed with water and then dried. 5 ml of the catalyst prepared in this way are together with 10 ml of benzene, Place 10 ml of acetic acid and 0.5 ml of commercially available concentrated nitric acid in a 50 ml pressure vessel. This

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The pressure vessel is then pressurized with oxygen up to a pressure of 40 atmospheres via a valve in the upper part and placed in an oil bath at 100 ^° C. for 16 hours on a shaking device. The reaction mixture contains phenyl acetate in a yield of $ 2.7, based on the benzene used ($ 530, based on palladium) and, as a by-product, $ 1.1, based on the benzene used, nitrobenzene;

Example 6 '

A solution of 0.1 g of palladium acetate in acetic acid is evaporated to dryness with 10 ml of granulated activated charcoal. Then 10 ml of the catalyst prepared in this way together with 5 ml of benzene, 10 ml of acetic acid and 0.5 ml of commercially available concentrated nitric acid according to Example 5 are heated ^{to 100 ° C. at an oxygen pressure of 50 atmospheres for 16 hours.} The yield of phenyl acetate is 4.6 ° β>, based on benzene ($ 400, based on palladium). The reaction mixture contains 1.8 $ nitrobenzene, based on the benzene used.

Example 7

A solution of 0.2 g of palladium nitrate in dilute nitric acid is evaporated to dryness with 10 ml of granulated silica gel. 10 ml of the catalyst prepared in this way are heated together with 5 ml of benzene, 10 ml of acetic acid and 0.3 ml of commercially available concentrated nitric acid under an oxygen pressure of 40 atmospheres at 110 ^° C. for 3 hours. The reaction mixture contains phenyl acetate in a yield of 2.7%, based on the benzene used (265 °, based on palladium), and 0.9 % nitrobenzene, based on the benzene used. After the analysis, the reaction mixture is

1 0.9-8 5 1/19 1-9

returned to the reaction vessel and, after adding a certain amount of oxygen, subjected to another 15-hour reaction. This reaction mixture contains phenyl acetate in a yield of $ 8.7, based on benzene ($ 855> based on palladium), and 2.9 % nitrobenzene, based on benzene.

When example 7 is repeated with the omission of the saltpeter

Acid is obtained after 3 hours of reaction time 0.4 i ° phenyl acetate, based on benzene, and after 18 hours reaction time 1.0 9 ^ phenyl acetate, based on benzene (98 °, based on palladium), in addition to a little nitrobenzene. If the reaction time is increased further, the yield does not increase any further.

Example 8

A reaction tube made of hard glass (internal diameter, 30 cm length) is charged with 10 ml of the catalyst from Example 5. The reaction tube is set to a Inneritemperatur of 150 ⁰ C and under atmospheric pressure with a gas mixture of benzene, acetic acid, oxygen and concentrated nitric acid (molar ratio 10s20: 20s1) with a flow rate of 60 mL / min, charged. 2 hours after the start of the reaction, the phenyl acetate yield is $ 1.8, based on benzene (single pass). Even after a reaction time of 15 hours or longer, no decrease in the catalyst activity can be observed. The amount of nitrobenzene formed is 0.8 <fo- _t based on benzene (single pass).

Example 9

A solution of 0.17 g of palladium chloride in dilute hydrochloric acid is evaporated to dryness with 10 ml of granulated silica gel. That

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dried product is reduced with alkaline hydrazine hydrate, carefully washed with water and dried. 5 ml of the catalyst thus prepared are placed in a 50 ml pressure vessel together with 10 ml of toluene, 10 ml of acetic acid and 0.5 ml of commercially available concentrated nitric acid. This . is pressurized with oxygen up to a pressure of 40 atm via a valve in the upper part and placed in an oil bath of 100 ⁰ G for 16 hours on a shaking device. The following yields result from the analysis: o-tolyl acetate 0.65 / m-tolyl acetate 0.43 #, p-tolyl acetate 1.62% , benzaldehyde 0.23 #, each based on the toluene used. In addition, $ 0.23 nitrotoluene, based on the toluene used, is obtained as a by-product.

Examples. 10 to 19

According to Example 9, the alkylbenzenes listed in Table II are used using in each case 5 ml of the catalyst from Example 9 and an oxygen pressure of 40 atm the corresponding Aryl acetates produced. The results are in Table II compiled.

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Table II

At- alkyl- acetic- nitric- temperature reaction example benzene acid or ratur onszeit Nr, (ml) (ml) alkali nitrate C ⁰ C) (hrs.)

Main product

-U-

Yield {%) based on alkyl pallabenzol dium

10 Ethyl- 20th benzene (10) 11 o-diethyl 20th O benzene Φ (10) CO W. 12th m-diethyl 35 _ι benzene *% » (5) IO 13th p-diethyl 5 IO benzene (20)

HHO ₃ , 0.5 ml

100

100

150 o-ethylphenyl acetate
p-ethylphenyl acetate

3,4-diethylph.enyl acetate

2Q 2,4-diethylphenyl acetate
3.5-3 diethylplienyl acetate

2,5-diethylphenyl acetate

0.5 1.4

0.9

1.7 1.0

0.8

¹⁰ CsUO ₅ , 0.3 g 100 10 3,4-dimethylphenylacetaf 2.5

15th

16

10

10

0.3 g, 120

110 2,4-dimethylphen37-la.ee tat
3,5-disiethylphenyl acetate

2,5-dimethylphenyl acetate '

1.1 0.8

0.9,

Table II ('continued)

For- alkyl- acetic-, nitric acid benzene acid or no. (Ml) (al) alkali nitrate (° 0)

Temperature reaction time

(Hours.).

Main product

- 15

Yield $)
based on

Alkyl pallabenzol dium

o-ethyl "17 toluene (10)

20th

, 0.1 g of 3-methyl-4-ethylphenylaoetat 1,6
3-ethyl-4-methylphenyl acetate 1,2

18th

- *

in-ethyltoluene (10)

p-ethyltoluene (10)

20th

20th

ENT ,, 0.1 ml

2-methyl-4-ethylphenyl acetate 0.8
2-ethyl-4-methylphenyl acetate 0.5

290

J _n 2-methyl 1-5-ethylphenyl acetate 0.4 ' _1πς
^IU 2-ethyl-5-methylphenyl acetate .0.3 °

CD hO OQ

Example 20

0.1 g of palladium nitrate and 0.2 g of lithium nitrate are in water dissolved and evaporated to dryness with 10 ml of granulated silica gel . ,

A reaction tube made of hard glass (10 mm internal diameter, 300 mm length) is charged with 10 ml of the aforementioned catalyst

* '. ο and set to an internal temperature of 50 0. In this Reaction tube is a gaseous mixture of benzene, acetic acid, Oxygen and concentrated nitric acid (molar ratio 10: 20 ': 30: 1) under normal pressure with a flow rate of 60 ml / min. 3 hours after the start of the Reaction are the yields of phenyl acetate and nitrobenzene 1.2 or 0.2 $ for a single pass, each based on the amount used Benzene.

Example e 21 to 28

Under the general conditions given in Example 20 and the specific conditions given in Table III, the aryl acetates shown in Table III. Bie yields are determined 3 hours after the start of the reaction in a single pass and are based in each case on the benzene used.

The catalysts listed in Table III are according to the example 20 made.

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Table III

Reaction conditions

at
game
No. catalyst
components
■ '(amount). · Composition of
Starting mixture (mole)
Ben- Vinegar- Sour- Salpe-
zol acid substance tertiary acid 30th 50 2 Temp.
ro) Space
Schwin
age%
(StdT ^T) Yields (° ß>)
Phenyl uritro
acetate benzene 0.3 Phenyl
acetate,
selectivity
in i <> 21st Pd (0.1 g), Cs- for-
miat (0.3g),
SiO ₂ (10 ml) 5 30th 50 2 180 450 2.0 0.1 87 »
22nd Pd (0.1 g)
Li formate (0.5 g)
Al ₂ O ₅ (IO ml) 10 30th 50 2 180 600 0.9 90 Pd (0.1 g)
jJa acetate (0.2 g)
SiO ₂ (10 ml) '5 10 30th 1 180 450 1.7 0.2 89 24 Pd (0.1 g)
K-acetate (0.2 g)
SiO ₂ ZAl ₂ O ₅ (5 ml) 10 10 30th 1 190 300 1.4 0.4 88 25th Pd (0.2 g)
Rb acetate (0.2 g)
SiO ₂ (10 ml) 5 170 400 2.3

Table III (continued)

With », catalyst game · .. components J
No. (quantity)

O 26th Pd (0.1 g
Gs-acetate (0,
Activated carbon (1 1 g)
0 ml) co
- - 351/19 27 • Pd acetate (0.1
Na acetate (0.1
K-acetate (0.1
SiO ₂ (10 ml) ^G
G) Pd (N0 ₃ ) ₂ (0.1 G) 28 Cs acetate (0,
Al ₂ O ₃ (5 ml) 2 g)

Kon «

^Si0

(0.1

Reaction conditions

Composition of the starting mixture (mol)

Ben- Acetic- Sour- Salpezol acidic acid

20 20

10 30

20th

10

50

50

5 30 ■ 50

Temp. Space
Schwin
age Yields ($)
Phenyl nitro
acetate benzene *
0.2 Phenyl
acetate,
Selectivi
ity in <fo 150
• 450 ■ 1.5 0.1 88 ■ 150 900 0.7 0.5 • 87 "
• 170 . 300 2.5 1.1 81 180 450 1.9 63

Claims (1)

P at en t "a * η s ρ r ü c he Process for the preparation of aryl acetates, thereby g e k e η η draws that one is a benzene of the general Formula (I) (D in which R ₁ and R _{2 are} identical or different and denote a hydrogen atom or a lower alkyl radical with 1 to 4 carbon atoms, ', with acetic acid in the presence of a molecular oxygen-containing gas and metallic palladium or a palladium compound, as well as nitric acid or an alkali nitrate Brings temperatures of 30 to 300 ⁰ C to implement. 2, The method according to claim 1, characterized in that one as the palladium compound, an oxide, hydroxide or nitrate of palladium used. " 3 · Method according to claim 1, characterized. that T. man the palladium compound is an acetate or propionate of palladium used. 4. The method according to claim 1, characterized in that one as alkali nitrate a nitrate of lithium, sodium, potassium, rubidium or cesium used, - ■ 5. The method of claim _f,:; characterized in that the nitric acid or the Alkflinitrat the reaction system directly in a Men ^ e. of; Ö, 2 blfeö -,: Ö01 mol, preferably 0.1 to 0.002 mol, per mole of acetic acid, is added. 109851/1919 6o method according to claim 1 .. characterized in that one · the nitric acid or the alkali nitrate the catalyst in 'one Amount of 0.0.1 to 15 moles, preferably 0.03 to 10 moles, per Gram atom of palladium, added. 7. The method according to claim 1, characterized in that the palladium or the palladium compound is an alkali salt of a aliphatic carboxylic acid added. 8. 'The method according to claim 7, characterized in that one a formate, acetate or propionate of lithium, sodium ,. Potassium, Rubidium or Cesium used. 9. The method according to claim 7 and 8, characterized in that that one has an atomic ratio of alkali metal to palladium of 30: 1 to 0.1: 1, preferably 10: 1 to 0.5: 1, is used. 109851/1919