NL8101686A - SELECTIVE PREPARATION OF PHENYLENE DIACETATE. - Google Patents

Description

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Selective preparation of phenylene diacetate.

The invention relates to a process for the preparation of phenylene diacetate, in particular to the conversion of phenyl acetate to phenylene diacetate by a palladium catalyst in the presence of oxygen, acetic anhydride and acetic acid at elevated temperature and pressure. More particularly, the invention relates to a process for preparing para-phenylene diacetate as the main product. Phenylenediacetate can be used as a solvent. The preparation of phenyl acetate is described in U.S. Patent No. 10k 156,783.

The acetoxylation of chlorobenzene by palladium diacetate in acetic acid with an oxygen atmosphere and with or without the presence of NOg and with meta selectivity is reported in Acta Chemica Seandinavica B28 (197 * 0 771-776, where Ac is the group CH 2 CO-. Also disclosed herein is the stoichiometric acetoxylation of phenylacetate by 2.2 * -Bipy Pd (0Ac) (10 ^) in acetic acid at 115 ° C in an oxygen atmosphere with meta-diacetoxybenzene (meta-phenylene diacetate) as main product (cO5) after a reaction time from 2 hours On pages 597-602 of the same literature it is stated that a heterogeneous gas phase acetoxylation of a monofunctional benzene derivative, which takes place in acetic acid in the presence of oxygen, shows a reversal of the normal substitution effect, ie ortho, para-targeting substituents mainly give meta acetoxylation and meta targeting give ortho, para acetoxylation.

Formation of methyl benzyl acetate via the homogeneous reaction between palladium (II) acetate and paraxylene in acetic acid in the presence of oxygen has been studied and reported in articles in Acta Chemica Seandinavica 27, 1973, pp. 1162-117 **, 30 12U9-I25U, 1255 -1267. The acetoxylation of phenyl acetate by potassium peroxide disulfate with palladium (II) as a catalyst in 81 81 686 L 1.

The presence of acetic acid to form 25% ortho, b2% meta and 33% para isomers of phenylene diacetate is disclosed in Acta Chemica Scandinavica B30 (1976) biz. 361-36 ^.

The use of palladium (il) (along with other components such as oxidants, co-oxidants) to catalyze aromatic acetoxylation is reported in the literature, such as, for example, U.S. Pat. No. 3,772,383; Tetrahedron Letters No. 58, 6123-6126, 1968, J. Org. Chem., Vol. 36, No. 1191, and J.S.C. Chem. Coram. 197 ^ p.

10 885-886.

The acetoxylation of benzene to phenyl acetate using oxygen, pdladium on silica or aluminum oxide in the presence of acetic acid is reported in Erdöl und Kohle, 23, 79, 1970.

According to Journal of Organic Chemistry, Vol. 33, November 11, 1968, acetoxylation of toluene in the presence of oxygen, palladium acetate and an alkali carboxylate at elevated temperature results in a benzyl acetate and at higher conversions to benzylidene diacetate.

However, none of the aforementioned references disclose or suggest the conversion of phenyl acetate to phenylenediacetate by the present method. In contrast to the previously discussed reference Acta Chemica * "fandcandinaviea" -28, p. 597-602, p. 771-776, the process of the invention further predominantly provides the para-phenylene diacetate isomer.

According to the method of the invention, phenyl acetate is reacted in the presence of acetic anhydride, acetic acid, an acetoxylating amount of oxygen and a palladium catalyst at an elevated temperature and pressure to phenylene diacetate according to the reaction scheme A on the formula sheet. Paraphenylene diacetate is the predominant product, followed by the ortho and meta isomers.

The term "acetoxylation" used herein means the addition of an acetoxy group CH 2 COO- to the

O

\ 81016 8 6 - 3 - Organic compound in question.

The process of the invention is suitably carried out under an acetoxylation sterilizer, which is a temperature which favors the formation of phenylene diacetate. Elevated temperatures of 100-300 ° C are preferred, and most preferably 150-2500 ° C. The reaction proceeds in a liquid phase. An acetoxylation pressure is also preferably used up to a maximum of about 10.3 MPa. The reaction time varies considerably depending in part on the processing conditions, including, for example, the relative concentrations of materials, the temperature and the pressure.

The method can also be carried out continuously.

The phenyl acetate is desired to react in the presence of acetic acid and acetic anhydride. The acetic anhydride should desirably be present in an amount of 0.1-3 times the weight, preferably 0.3-1.5 times the weight of phenyl acetate. The nol ratio of palladiol catalyst to phenyl acetate should be in the range of 0.0001-1, preferably 0.001-0.5.

Oxygen is used in the present acetoxylation process. The amount of oxygen is an amount of acetoxylation, that is, an amount that promotes the formation of phenyl diacetates, desirably the nara isomer, in the presence of a palladium catalyst, acetic acid and acetic anhydride.

Generally, the oxygen used may be in an inert gas, such as nitrogen, and may be of a low concentration in such a mixture. For example, in the following example, a gas mixture of h% oxygen and 96% nitrogen was used.

The palladium catalyst is desirably palladium-on-alumina. Other palladiura catalysts, preferably palladium acetate and palladium on other supports, for example, carbon and silica, which would lead to an effective reaction mixture, can be used.

In general, the present process leads to the conversion of phenyl acetate substantially into phenylene diacetate 35, the predominant isomer being the paraisomer. Although a product% \ 8101685 k "____ _ Ή

V

- U _ can be produced other than phenylene diacetate, the amount will be immune, if not mere trace. The selectivity for paraphenylene diacetate is also considerable, for example in the example test, where it is 82%.

The invention will now be illustrated with the following example:

Example

The following reaction is carried out in a stirred stainless steel autoclave using 5% palladium-on-alumina (2.35mmol) as the catalyst, 510mmol acetic anhydride, 950mmol phenylacetate and 1 * 200mmol acetic acid. The autoclave was heated to 200 ° C under 5.6 MPa of nitrogen. Then an acetoxylation gas, U% oxygen and 96% nitrogen, is passed through the heated mixture for 2.5 hours at a rate of 2 l / min (5.6 MPa). At the end of the test, the autoclave is cooled to room temperature and the products are analyzed by gas chromatography. The total product yield is 800% based on palladium. Gas chromatographically, three products are discovered: orthophenylene diacetate, ih% 20 selectivity, metaphenylene diacetate with a selectivity of 1% and paraphenylene diacetate with a selectivity of 82%.

Only a trace of any acetylation products had been found.

The phenylene diacetates can be recovered and separated • known methods such as distillation and / or crystallization. • · "/ - ·" ··: ". V -" · <- '^ $ 001 ···. The term "selectivity" as used herein means the mole percentage of one isomer relative to all the products formed.

The foregoing yields indicate that the para isomer is the major diacetate product, while the ortho isomer is a minor diacetate product. The meta isomer is present in a nominal amount. These amounts can be modified by changes in operating conditions, but the para isomer is generally favored and can be the predominant isomer.

Use of other post-catalyst catalysts, for example palladium acetate, and use of other operating conditions lead to analog yields and selectivities.

k ----- V 81 016 8 6

Claims (5)

1. A method of acetoxylating phenyl acetate, characterized in that phenyl acetate is reacted with an acetoxylating amount of oxygen under elevated temperature and pressure in the presence of acetic acid, acetic anhydride and palladium catalyst. 2. Process according to claim 1, characterized in that paraphenylene diacetate is recovered as the main product. Process according to claim 1, characterized in that a temperature of 100-300 ° C is used. H. Process according to claim 1, characterized in that a molar ratio of catalyst to phenylacetate is used in a range of 0.0001 - 1. Process according to claim 1, characterized in that an amount of acetic anhydride is used in it ranges from 0.1-3 times the weight of phenyl acetate. 6. Process according to claims 1 to 5, characterized in that the palladium catalyst used is palladium-on-aluminum oxide, palladium acetate, palladium-on-silica, palladium-acetate-on-silica or palladium-on-carbon. 7. Process for preparing paraphenylene diacetate, characterized in that phenyl acetate is reacted with an acetoxylating amount of oxygen in the presence of acetic anhydride, palladium-on-alumina catalyst and acetic acid at a temperature in the range of 100-300 ° C and an increased pressure and wherein the acetic anhydride is present in an amount of 0.1-3 times the weight of phenyl acetate, and the molar ratio of catalyst to phenyl acetate is in a range of 0.0001-1. \ 8101686 \ z. * V. - f - V -A- o 2 ff II oc— ch3 o-c — ch3 a, Pd ΓΛ 4 CHjCOjH 4, / 20i 4 (cHjC0) j 0 CHj COf jf ^ OC-CH3 II o Smtech, Ine., / , Philadelphia, Pennsylvania, USA St. America 81 01 686 1, '' L,