CA1175058A - Selective production of phenylene diacetate - Google Patents
Selective production of phenylene diacetateInfo
- Publication number
- CA1175058A CA1175058A CA000373714A CA373714A CA1175058A CA 1175058 A CA1175058 A CA 1175058A CA 000373714 A CA000373714 A CA 000373714A CA 373714 A CA373714 A CA 373714A CA 1175058 A CA1175058 A CA 1175058A
- Authority
- CA
- Canada
- Prior art keywords
- palladium
- oxygen
- phenyl acetate
- amount
- acetate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
- C07C67/05—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation
- C07C67/055—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation in the presence of platinum group metals or their compounds
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Phenyl acetate is converted to phenylene diacetate by a palladium catalyst in the presence of an acetoxylation amount of oxygen, acetic acid and acetic anhydride at elevated temperatures and pressures The predominant product is the para-isomer. Phenylene diacetate can have utility as a solvent.
Phenyl acetate is converted to phenylene diacetate by a palladium catalyst in the presence of an acetoxylation amount of oxygen, acetic acid and acetic anhydride at elevated temperatures and pressures The predominant product is the para-isomer. Phenylene diacetate can have utility as a solvent.
Description
BACXGROUND OF THE INVENTION
i~
This invention relates to a process for the prepara-tion of phenylene diacetate. More particularly the invention relates to the conversion of phenyl acetate to phenylene diace-tate by a palladium catalyst in the presence of oxygen, acetic anhydride and acetic acid at elevated temperatures and pressures.
S~ill mcre par~icularly the invention xelate~ to a method of preparing ~ara phenylene diac~tate as a majvr produc~. Pheny-lene diacetate may have utility as a solvent. Preparat1on of phenyl acetate i5 disclo~ed in U.S. Patent No. 4,156,7&3.
The acetoxylation of chlorobenz~ne by Pd~OAc)2 in acetic acid with an oxygen atmosphere and with and without the presence of N02 and with me a - selectivity is reported in 11 ~5~58 Acta Chemica Scandinavica B28 (1974~ 771-776, L. Eberson et al Ac as used herein refers to the~group CH3-C-. The latter o also discloses the stoichiometric acetoxylation of phenyl acetate by 2,2'-Bipy Pd(OAc) (NO3) in acetic acid at 115~C in an oxygen atmosphere with meta-diacetoxybenzene (meta-phenylene diacetate) the major product (60%) after a reaction period of
i~
This invention relates to a process for the prepara-tion of phenylene diacetate. More particularly the invention relates to the conversion of phenyl acetate to phenylene diace-tate by a palladium catalyst in the presence of oxygen, acetic anhydride and acetic acid at elevated temperatures and pressures.
S~ill mcre par~icularly the invention xelate~ to a method of preparing ~ara phenylene diac~tate as a majvr produc~. Pheny-lene diacetate may have utility as a solvent. Preparat1on of phenyl acetate i5 disclo~ed in U.S. Patent No. 4,156,7&3.
The acetoxylation of chlorobenz~ne by Pd~OAc)2 in acetic acid with an oxygen atmosphere and with and without the presence of N02 and with me a - selectivity is reported in 11 ~5~58 Acta Chemica Scandinavica B28 (1974~ 771-776, L. Eberson et al Ac as used herein refers to the~group CH3-C-. The latter o also discloses the stoichiometric acetoxylation of phenyl acetate by 2,2'-Bipy Pd(OAc) (NO3) in acetic acid at 115~C in an oxygen atmosphere with meta-diacetoxybenzene (meta-phenylene diacetate) the major product (60%) after a reaction period of
2 hours. The aforementioned reference, pages 597-602, states that a heterogenous gas phase acetoxylation of amonofunctional benzene derivative that takes place in acetic acid in the presence of oxygen shows a reversal of the normal substitutent effect, i.e., ortho-, ~ -directing substituents give pre-dominantly meta-acetoxylation and meta-directing ones give ortho-, para-acetoxylation.
Formation of methylbenzylacetate via the homogeneous reaction between palladium(II) acetate and ~ -xylene in acetic acid in the presence of oxygen has been studied and reported in articles in Acta Chemica Scandinavica 27, 1973, L. Eberson et al., pages 1162-1174, 1249-1254, 1255-1267. The acetoxylation of phenyl acetate by potassium peroxydisulfate with Pd~II) as a catalyst in the presence of acetic acid to form 25~ ortho-, 42% meta- and 33% ~ -isomers of phenylene diacetate is disclosed in Acta Chemica Scandina~ica B30 (1976 pages 361-364, Eberson et al.
The use of palladium(II) lalong with other components such as oxidants, cooxidants) to cataly~e aromatic acetoxylation is reported in the literature as exemplified by U.S~ Patent No.
Formation of methylbenzylacetate via the homogeneous reaction between palladium(II) acetate and ~ -xylene in acetic acid in the presence of oxygen has been studied and reported in articles in Acta Chemica Scandinavica 27, 1973, L. Eberson et al., pages 1162-1174, 1249-1254, 1255-1267. The acetoxylation of phenyl acetate by potassium peroxydisulfate with Pd~II) as a catalyst in the presence of acetic acid to form 25~ ortho-, 42% meta- and 33% ~ -isomers of phenylene diacetate is disclosed in Acta Chemica Scandina~ica B30 (1976 pages 361-364, Eberson et al.
The use of palladium(II) lalong with other components such as oxidants, cooxidants) to cataly~e aromatic acetoxylation is reported in the literature as exemplified by U.S~ Patent No.
3,772,383; Tetrahedron Letters No. 58, pp. 6123-6126, 1968, C.H. Bushweller; ~. Org. Chem., Vol. 36, No. 14, 1971, P.M.
Henry; and ~.S C. Chem. Comm. 1974, pages 885-886, L. Eberson et al.
_ ~ _ ~75~5~
The acetoxylation of benzene to phenyl acetate using oxygen, palladium on silica or alumina in the presence of acetic acid is reported in Erdol Und Kohle, 23, 79, 1970.
According to Journal of Grganic Chemistr~, Vol. 33, November 11, 1968, D.R. Bryant et al. acetoxylation of toluene in the presence of oxygen, palladium acetate and an alkali metal carboxylate at elevated temperatures results in a henzyl acetate and at higher conversions to ben~ylidene diacetate.
However, none of the previously mentioned references disclose or suggest the conversion of phenyl acetate to phenylene diacetate via applicants' method. Further contrary to the previously discussed reference (~cta Chemica Scandinavica B-28, pages 597-602 and pages 771-776), applicants' method yields predominantly the ~ phenylene diacetate isomer.
SUMMARY
As aforestated, the process of this invention comprises reacting phenyl acetate in the presence of acetic anyhdride, acetic acid, an acetoxylation amount of oxygen and a palladium catalyst at an elevated temperature and pressure to yield phenylene diacetate in accordance with the following reaction:
O O
O-C CH O-C-C~3 ~ + 1~2 2 ~ (C~3CO)2O ~ ~ ~H3CO
o ;:. - 3 -~sv~
Para-phenylene di.acetate is the predominant product ~ollowed ~y .
the ortho- and m~ta-isomers.
description The word "acetoxylation" as used in this specification refers to the addition of an acetoxy group, CH3-C-O-, to the o organic compound being processed.
The process of this invention is conveniently carried out under an acetoxylation temperatùre which is th`e temperature which favors the formation of phenylene.diacetate. Elevated temperatuxes of from about 100C ~o about 300C are preferred and more preferably from about 150C to about 250C. The reac~ion is in a liquid phase. Also an acetoxyla~ion pres~ure is used. Reaction pressures of about up to 1500 p~ig are preferred. The period for the reaction ranges varias consider-ably, depending in part on the operating conditions, including for example, relative concentration~ of materials, tempera~ures, and pressure employed. The process can al50 be carried out in a continuous system.
The phenyl acetate should de~irably be reacted in the presence of acetic acid and acetic anhydride. The acetic anhydride should desirably be present in the amount of about 0.1 to about 3 times by weight of the amount of phenyl ac~tate used with 0.3 to 1.5 preferreda The molar ratio o~ palladium catalyst to phenyl acekate employed should be in ~he range between from about .0001 to about 1 with .001 to 0.5 preferr~d.
Oxygen is used in applicants' acetoxylation proce~s.
The amount of oxygen is an a etoxyla~ion amount, tha~ i~, an ~sass amount which favors th~ formation of phenylene diare~ate3, desirably the ~ isomer, in the presence of a palladium catalyst, acetic acid and acetic anhydride. Genexally the oxygen used can be co~tained in an inert gas such as nitrogen and in such a mixtuxe can be at a low concentration. For example, as reported in the Example, a gas mix~ure containing 4~ 2 and 96~ N2 was effectively used.
The palladium catalyst is desirably palladium on alumina. Other palladium catalysts, eOg., palladium acetate and palladium on other qupports, e.g., carbon and silica, which would result in an effective reaction mixture, can be used.
Generally, applicants' method results in converting phenyl acetate substantially to phenylene diacetate with the isomer the predominant isomer. While a product other than phenylene diacetate may be produced the amount will be minor, if not merely a trace. The selectivity as to ~ -phenylene diacetate is al~o substantial, for example, in the run in the Example, it was 82~.
The following example is provided to illustrate ths invention described herein.
EXAMPLE
The following reaction was run in a stirred stainless steel autoclave using 5% palladium on alumina (2.35 mmoles) as the catalyst, acetic anhydride (510 m~oles), phenyl acetate (950 mmoles) and acetic acid (4200 mmoles). The autoclave was heated to 200C under nitrogen (800 psig). Then an acetoxyla~
tion gas, 4% 2 and 96% N2 was passed through the heated mixture for 2.5 hours at a rate of 2 liters per minute (80~ psig~. At 1175~5~3 the end of the run the autoclave was cooled to room temperature and the products were analyzed by gas chromatography. Total product yield was 800% based on Rd. By gas chromatograph three products were detected: ortho-phenylene diacetate 14% selectivity, meta-phenylene diace~ate 4~ selectivi~y and para-phenylene diacetate 82% selectivity~ Just a trace of any acetylation product was found. The phenylene diacetates can be recovered and separated by known methods such as distillation and~or crystallization.
Selectivity as used herein is defined as the mole percent of one isomer to al~ products formed.
The foregoing yield~ indicate that the ~ omer 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, however, generally the ~ isomer is favored and can be the predominant isomer.
Use of other palladium catal~st, e.g., palladium acetate, and use of other operating conditions resulted in analogous yields and ~electivities.
~1'750~
SUPPLEMENTARY DISCLOSUl~E
In accordance with the teaching of the Principal Disclosure a process is provided for the acetoxylation of phenyl acetate to prepare para-phenylene diacetate by reacting phenyl acetate with an acetoxylating amount of oxygen in the presence of acetic anhydride, palladium and acetic acid at elevated temperatures and pressures.
Now, in accordance with the Supplementary Disclosure a process is provided which romprises reacting at elevated temperature and pressure, phenyl acetate, acetic anhydride and acetic acid in the presence of a palladium catalyst and a gas mixture, which gas mixture contains an inert gas and no more than 13 volume % oxygen, to yield phenylene diacetate in accordance with the following reaction:
O O
O-C-CH ~-C-CH3 ~ ~ 1/2 2 + (~l3C)2 CH3CO2E ~ -C-CH 3C2~1 AS either acetic acid or acetic anhydride, or both can be the source of the secsnd group which bonds to the phenyl acetate, the foregoing reaction scheme is merely re-presentative of the possible reactions which may occur.
Para-phenylene diacetate is the predominant product followed by the ortho- and meta-isomers.
The process is conveniently carried out in liquid phase under acetoxylation conditions, that is, at temperature~, pressures and oxygen levels which favor the formation of phenyl ene diacetate. Temperatures of from about 100C to about 300C
~175~S8 are preferred and pressures of from about 100 psig up to about 150Q psig. The reaction time may vary considerably, depending in part on the operating conditions, including, for example, catalyst, relative concentrations of materials, and the tem-perature and pressure. The process can be carried out in a batch, continuous or semi-continuous system.
The amount of acetic ~cid is not critical. A
preferred range is from 0.2 to about 5.0 moles per mole of phenyl acetate. The amount of oxygen is an acetoxylation amount, that is, an amount which favors the formation of phenylene diacetates, desirably the para-isomer, rather than the acetoxyacetophenone of copending application 373,935. Generally the oxygen is used in admixture with an inert gas such as nitrogen. The oxygen content of the gas mixture should be maintained at a low concentration, for example, not more than 13 volume %, preferably about 1-8 volume %, most preferably about 3-5 volume %. Above 13 Volume % the oxy-acetylation reaction of the copending application 373,935 will dominate.
Henry; and ~.S C. Chem. Comm. 1974, pages 885-886, L. Eberson et al.
_ ~ _ ~75~5~
The acetoxylation of benzene to phenyl acetate using oxygen, palladium on silica or alumina in the presence of acetic acid is reported in Erdol Und Kohle, 23, 79, 1970.
According to Journal of Grganic Chemistr~, Vol. 33, November 11, 1968, D.R. Bryant et al. acetoxylation of toluene in the presence of oxygen, palladium acetate and an alkali metal carboxylate at elevated temperatures results in a henzyl acetate and at higher conversions to ben~ylidene diacetate.
However, none of the previously mentioned references disclose or suggest the conversion of phenyl acetate to phenylene diacetate via applicants' method. Further contrary to the previously discussed reference (~cta Chemica Scandinavica B-28, pages 597-602 and pages 771-776), applicants' method yields predominantly the ~ phenylene diacetate isomer.
SUMMARY
As aforestated, the process of this invention comprises reacting phenyl acetate in the presence of acetic anyhdride, acetic acid, an acetoxylation amount of oxygen and a palladium catalyst at an elevated temperature and pressure to yield phenylene diacetate in accordance with the following reaction:
O O
O-C CH O-C-C~3 ~ + 1~2 2 ~ (C~3CO)2O ~ ~ ~H3CO
o ;:. - 3 -~sv~
Para-phenylene di.acetate is the predominant product ~ollowed ~y .
the ortho- and m~ta-isomers.
description The word "acetoxylation" as used in this specification refers to the addition of an acetoxy group, CH3-C-O-, to the o organic compound being processed.
The process of this invention is conveniently carried out under an acetoxylation temperatùre which is th`e temperature which favors the formation of phenylene.diacetate. Elevated temperatuxes of from about 100C ~o about 300C are preferred and more preferably from about 150C to about 250C. The reac~ion is in a liquid phase. Also an acetoxyla~ion pres~ure is used. Reaction pressures of about up to 1500 p~ig are preferred. The period for the reaction ranges varias consider-ably, depending in part on the operating conditions, including for example, relative concentration~ of materials, tempera~ures, and pressure employed. The process can al50 be carried out in a continuous system.
The phenyl acetate should de~irably be reacted in the presence of acetic acid and acetic anhydride. The acetic anhydride should desirably be present in the amount of about 0.1 to about 3 times by weight of the amount of phenyl ac~tate used with 0.3 to 1.5 preferreda The molar ratio o~ palladium catalyst to phenyl acekate employed should be in ~he range between from about .0001 to about 1 with .001 to 0.5 preferr~d.
Oxygen is used in applicants' acetoxylation proce~s.
The amount of oxygen is an a etoxyla~ion amount, tha~ i~, an ~sass amount which favors th~ formation of phenylene diare~ate3, desirably the ~ isomer, in the presence of a palladium catalyst, acetic acid and acetic anhydride. Genexally the oxygen used can be co~tained in an inert gas such as nitrogen and in such a mixtuxe can be at a low concentration. For example, as reported in the Example, a gas mix~ure containing 4~ 2 and 96~ N2 was effectively used.
The palladium catalyst is desirably palladium on alumina. Other palladium catalysts, eOg., palladium acetate and palladium on other qupports, e.g., carbon and silica, which would result in an effective reaction mixture, can be used.
Generally, applicants' method results in converting phenyl acetate substantially to phenylene diacetate with the isomer the predominant isomer. While a product other than phenylene diacetate may be produced the amount will be minor, if not merely a trace. The selectivity as to ~ -phenylene diacetate is al~o substantial, for example, in the run in the Example, it was 82~.
The following example is provided to illustrate ths invention described herein.
EXAMPLE
The following reaction was run in a stirred stainless steel autoclave using 5% palladium on alumina (2.35 mmoles) as the catalyst, acetic anhydride (510 m~oles), phenyl acetate (950 mmoles) and acetic acid (4200 mmoles). The autoclave was heated to 200C under nitrogen (800 psig). Then an acetoxyla~
tion gas, 4% 2 and 96% N2 was passed through the heated mixture for 2.5 hours at a rate of 2 liters per minute (80~ psig~. At 1175~5~3 the end of the run the autoclave was cooled to room temperature and the products were analyzed by gas chromatography. Total product yield was 800% based on Rd. By gas chromatograph three products were detected: ortho-phenylene diacetate 14% selectivity, meta-phenylene diace~ate 4~ selectivi~y and para-phenylene diacetate 82% selectivity~ Just a trace of any acetylation product was found. The phenylene diacetates can be recovered and separated by known methods such as distillation and~or crystallization.
Selectivity as used herein is defined as the mole percent of one isomer to al~ products formed.
The foregoing yield~ indicate that the ~ omer 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, however, generally the ~ isomer is favored and can be the predominant isomer.
Use of other palladium catal~st, e.g., palladium acetate, and use of other operating conditions resulted in analogous yields and ~electivities.
~1'750~
SUPPLEMENTARY DISCLOSUl~E
In accordance with the teaching of the Principal Disclosure a process is provided for the acetoxylation of phenyl acetate to prepare para-phenylene diacetate by reacting phenyl acetate with an acetoxylating amount of oxygen in the presence of acetic anhydride, palladium and acetic acid at elevated temperatures and pressures.
Now, in accordance with the Supplementary Disclosure a process is provided which romprises reacting at elevated temperature and pressure, phenyl acetate, acetic anhydride and acetic acid in the presence of a palladium catalyst and a gas mixture, which gas mixture contains an inert gas and no more than 13 volume % oxygen, to yield phenylene diacetate in accordance with the following reaction:
O O
O-C-CH ~-C-CH3 ~ ~ 1/2 2 + (~l3C)2 CH3CO2E ~ -C-CH 3C2~1 AS either acetic acid or acetic anhydride, or both can be the source of the secsnd group which bonds to the phenyl acetate, the foregoing reaction scheme is merely re-presentative of the possible reactions which may occur.
Para-phenylene diacetate is the predominant product followed by the ortho- and meta-isomers.
The process is conveniently carried out in liquid phase under acetoxylation conditions, that is, at temperature~, pressures and oxygen levels which favor the formation of phenyl ene diacetate. Temperatures of from about 100C to about 300C
~175~S8 are preferred and pressures of from about 100 psig up to about 150Q psig. The reaction time may vary considerably, depending in part on the operating conditions, including, for example, catalyst, relative concentrations of materials, and the tem-perature and pressure. The process can be carried out in a batch, continuous or semi-continuous system.
The amount of acetic ~cid is not critical. A
preferred range is from 0.2 to about 5.0 moles per mole of phenyl acetate. The amount of oxygen is an acetoxylation amount, that is, an amount which favors the formation of phenylene diacetates, desirably the para-isomer, rather than the acetoxyacetophenone of copending application 373,935. Generally the oxygen is used in admixture with an inert gas such as nitrogen. The oxygen content of the gas mixture should be maintained at a low concentration, for example, not more than 13 volume %, preferably about 1-8 volume %, most preferably about 3-5 volume %. Above 13 Volume % the oxy-acetylation reaction of the copending application 373,935 will dominate.
Claims (12)
1. A process for the acetoxylation of phenyl acetate comprising:
reacting phenyl acetate with an acetoxylation amount of oxygen at elevated temperatures and pressures in the presence of acetic acid, acetic anhydride and a palladium catalyst whereby para-phenylene diacetate is obtained as the predominant product.
reacting phenyl acetate with an acetoxylation amount of oxygen at elevated temperatures and pressures in the presence of acetic acid, acetic anhydride and a palladium catalyst whereby para-phenylene diacetate is obtained as the predominant product.
2 Process according to Claim 1 wherein the tem-perature is in the range between from about 100°C to about 300°C.
3. Process according to Claim 1 wherein the molar ratio of catalyst to phenyl acetate is in the range between from about 0.0001 to about 1.
4. Process according to Claim 1 wherein the acetic anhydride is present in the range between from about 0.1 to about 3 times by weight of the phenyl acetate.
5. Process according to Claims 1 or 2 wherein the palladium catalyst is selected from the group consisting of palladium on alumina, palladium acetate, palladium on silica, palladium acetate on silica and palladium on carbon.
6. Process according to Claims 3 or 4 wherein the palladium catalyst is selected from the group consisting of palladium on alumina, palladium acetate, palladium on silica, palladium acetate on silica and palladium on carbon.
7. A process for thepreparation of para-phenylene diacetate comprising:
reacting phenyl acetate with an acetoxylating amount of oxygen in the presence of acetic anhydride, palladium on alumina catalyst, and acetic acid and at a temperature in the range between from about 100°C to about 300°C
and an elevated pressure and wherein the acetic anhydride is present in the range between from about 0.1 to about 3 times by weight of the phenyl acetate, and the molar ratio of catalyst to phenyl acetate is in the range between from about 0.0001 to about 1.
reacting phenyl acetate with an acetoxylating amount of oxygen in the presence of acetic anhydride, palladium on alumina catalyst, and acetic acid and at a temperature in the range between from about 100°C to about 300°C
and an elevated pressure and wherein the acetic anhydride is present in the range between from about 0.1 to about 3 times by weight of the phenyl acetate, and the molar ratio of catalyst to phenyl acetate is in the range between from about 0.0001 to about 1.
8. A process for the acetoxylation of phenyl acetate which comprises reacting phenyl acetate with an acetoxylating amount of oxygen in the presence of a palladium catalyst,acetic acid and acetic anhydride whereby paraphenylene diacetate is produced as the predominant product.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
9. The process of Claim 1 wherein the oxygen is in admixture with an inert gas with the amount of oxygen in the gas mixture not exceeding 13 volume %.
10. The process of Claim 7 wherein the oxygen is in admixture with an inert gas with the amount of oxygen in the gas mixture not exceeding 13 volume %.
11. The process of Claim 8 wherein the oxygen is in admixture with an inert gas with the amount of oxygen oxygen in the gas mixture not exceeding 13 volume %.
12, The process of Claims 9, 10 or 11 wherein the amount of oxygen in the gas mixture is about 1% to about 8 volume %.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13770780A | 1980-04-07 | 1980-04-07 | |
| US137,707 | 1987-12-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175058A true CA1175058A (en) | 1984-09-25 |
Family
ID=22478714
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373714A Expired CA1175058A (en) | 1980-04-07 | 1981-03-24 | Selective production of phenylene diacetate |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5936972B2 (en) |
| BE (1) | BE888319A (en) |
| CA (1) | CA1175058A (en) |
| FR (1) | FR2479811A1 (en) |
| GB (1) | GB2073197B (en) |
| IT (1) | IT1195771B (en) |
| NL (1) | NL8101686A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3573598D1 (en) * | 1984-11-21 | 1989-11-16 | Hoffmann La Roche | Process for the preparation of hydrochinone derivatives |
| US4814110A (en) * | 1984-12-14 | 1989-03-21 | The Clorox Company | Method for esterifying dihydroxybenzenes |
| TR22733A (en) * | 1984-12-14 | 1988-05-24 | Clorox Co | MONTHED AND DIESTER PERASIT IPTIDAI SUBSTANCES |
| FI874163A (en) * | 1986-09-26 | 1988-03-27 | Mitsui Toatsu Chemicals | KATEKOLDERIVAT SAMT PREPARAT INNEHAOLLANDE DESAMMA FOER HAEMMANDE OCH BOTANDE AV REGRESSIVA SJUKDOMAR I DET CENTRALA NERVSYSTEMET. |
-
1981
- 1981-03-24 CA CA000373714A patent/CA1175058A/en not_active Expired
- 1981-03-26 IT IT20748/81A patent/IT1195771B/en active
- 1981-04-03 GB GB8110491A patent/GB2073197B/en not_active Expired
- 1981-04-06 NL NL8101686A patent/NL8101686A/en not_active Application Discontinuation
- 1981-04-07 BE BE0/204405A patent/BE888319A/en not_active IP Right Cessation
- 1981-04-07 FR FR8106922A patent/FR2479811A1/en active Granted
- 1981-04-07 JP JP56051300A patent/JPS5936972B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE888319A (en) | 1981-10-07 |
| GB2073197B (en) | 1984-10-24 |
| IT1195771B (en) | 1988-10-27 |
| JPS5936972B2 (en) | 1984-09-06 |
| IT8120748A0 (en) | 1981-03-26 |
| FR2479811B1 (en) | 1984-05-04 |
| FR2479811A1 (en) | 1981-10-09 |
| JPS56156234A (en) | 1981-12-02 |
| NL8101686A (en) | 1981-11-02 |
| GB2073197A (en) | 1981-10-14 |
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| MKEX | Expiry |