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Improved Process for the Preparation of Thioacetamide

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Improved Process for the Preparation of Thioacetamide Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 648 742 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Intel e C07C 327/42 of the grant of the patent: 22.01.1997 Bulletin 1997/04 (21) Application number: 93870201.6 (22) Date of filing: 14.10.1993 (54) Improved process for the preparation of thioacetamide Verbessertes Verfahren zur Herstellung von Thioacetamid Procede perfectionne pour la preparation du thioacetamide (84) Designated Contracting States: (74) Representative: Tanner, James Percival et al AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL ROHM AND HAAS (UK) LTD. PT SE European Operations Patent Department Lennig House (43) Date of publication of application: 2 Mason's Avenue 19.04.1995 Bulletin 1995/16 Croydon CR9 3NB (GB) (73) Proprietor: ROHM AND HAAS COMPANY (56) References cited: Philadelphia, Pennsylvania 19106-2399 (US) CA-A- 946 392 US-A- 3 979 452 (72) Inventor: Williams, Eric Lee St. Ann, Missouri 63074 (US) DO CM ^> Is- 00 ^- CO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU Printed by Jouve, 75001 PARIS (FR) 1 EP 0 648 742 B1 2 Description thioacetamide for subsequent reaction(s) such as that shown below. The present invention provides an improved proc- The reaction may be conducted in batches or as a ess for the production of thioacetamide from hydrogen continuous reaction, as in a tube reactor. The relative sulfide and acetonitrile. 5 amount of catalyst needed to efficiently carry out the present process will depend on the reactor size and con- Background of the Invention figuration, as well as the efficiency of mixing and heat exchange. The polymer-supported amine catalysts use- Thioacetamide is a commercially available chemi- ful in the present invention have a range of effective- cal having many industrial uses and is a versatile rea- 10 ness. The usual process development experimentation gent for further chemical synthesis. The reaction of hy- known to those of skill in the art will be needed to deter- drogen sulfide and acetonitrile to produce thioaceta- mine the optimum conditions; however, the examples mide is well known. U.S. Patent 2, 421, 031 discloses the below provide guidance as to effective combinations. use of a catalyst, 8-14 mesh Si02AI203 gel, at a tem- The polymer-supported amine catalyst may be any perature of about 500 °F to obtain yields of 85% based is polymer which has pendant amino functionalities. The on hydrogen sulfide. The reaction is also catalyzed by amine may be an alkyl or aryl amine or a heterocycle, various bases. Jaworski, et al., disclosed the use of tri- such as pyridine. The polymer-supported amine may al- ethylamine in a 220-hour reaction carried out in benzene so be cross-linked with a second polymer type. For ease or toluene (Polish J. Chem., 52(10): 2067-8, 1978). Gir- in removal and recycling it is preferred that the polymer- gis disclosed the use of amine catalysts, including sec- ic supported amine catalyst be insoluble in acetonitrile. ondary amines (Canadian Pat. No. 946,392, 1974; U.S. Examples are heterogeneous gels or macroreticular Pat. No. 3,852,287, 1974; U.S. Pat. No. 3,700,664, resins such as a poly(4-vinylpyridine) cross-linked with 1972). More recently, alkyl metal sulfides and hydro- a divinylbenzene polymer; a 25% cross-linkage has sulfides have been disclosed as catalysts for the reac- been found to be effective in the present invention. Fur- tion of aminonitriles with hydrogen sulfide for the pro- 25 ther example are polymers having pendant 4-dimethyl- duction of aminothioacetamides (Moder et al., EP 0 272 aminopyridine (DMAP) groups or 4-(N-benzyl-N-meth- 909). Moder et al. prefer these catalysts because the ylamino)pyridine (BMAP). The backbone polymer may amine base catalysts previously used are difficult to re- be, for example, a polystyrene. A polymer having DMAP move after completion of the reaction. groups is a preferred embodiment in the present inven- It is an object of the present invention to provide a 30 tion. high-yielding, cost-effective process to prepare thioa- Polymer-supported amine catalysts are available in cetamide with minimal post-reaction processing and re- many forms from many sources. One such source is usable catalysts. Reilly Tar & Chemical Corporation (Indianapolis). Ref- erences for how to make such polymer-supported Summary of the Invention 35 amine catalysts are discussed in PCT Application WO 90/03368 (April 1990), herein incorporated by refer- The present invention provides a process for pre- ence. European Patent Application 0 277 824 also dis- paring thioacetamide from hydrogen sulfide and ace- closes such polymer-supported amine catalysts and tonitrile in the presence of a polymer-supported amine their use in acetic acid production. catalyst. The reaction is run under pressure due to the 40 The polymer-supported amine catalyst has many use of hydrogen sulfide gas. The reaction temperature advantages. First, it is not soluble in acetonitrile and thus is not crucial, but for commercially reasonable reaction may be recovered from the reaction by filtration. Alter- times, it is preferred that the temperature be maintained natively, the reactants are exposed to a container of the between about 100 and 200 °C, although some decom- catalyst which is porous to the reactants but not the cat- position of the desired product may occur at the higher 45 alyst, such a basket suspended in a reaction vessel or temperatures. Thus, it is preferred that the temperature attached to the walls or baffles within a reaction tube. not exceed 150 °C, and more preferably it is maintained Second, the catalyst requires no regeneration step between about 120 and 130 °C. before it can be used again. Contamination with the re- actants or thioacetamide does not reduce its efficacy in Detailed Description of the Invention so succeeding reactions. Third, the reaction may be carried out at moderate temperatures which permit essentially The reactants used in the present invention are 100% yield with little or no decomposition. commercially available. They maybe used in essentially equimolar amounts or acetonitrile may be used in molar Example 1 excess to hydrogen sulfide. A molar excess of ace- 55 tonitrile will result in a product which is a solution of thio- A mixture of 500 ml_ of acetonitrile and 1 0 grams of acetamide in acetonitrile, which may facilitate handling Reilex® 425 or Reilly Poly-DMAP resin (Reilly Tar & the thioacetamide and may also be the desired form of Chemicals) is introduced into a one-liter autoclave. The 2 3 EP 0 648 742 B1 4 solution is stirred and heated to 110-130 °C. Hydrogen 4. The method of Claim 1 wherein acetonitrile is in mo- sulfide gas (34 g, 1.0 mol) is introduced. The pressure lar excess to hydrogen sulfide. decreases from about 1 0 x 1 05 Pa to 2.8 x 1 05 Pa (1 45 psi to 40 psi) as the hydrogen sulfide reacts with the 5. The method of Claim 1 wherein said polymer-sup- acetonitrile. The reaction takes from 2 to 18 hours, after 5 ported amine catalyst comprises 4-dimethylami- which the mixture is discharged from the reactor and fil- nopyridine groups pendant to a polymer backbone. tered. The filtrate is an approximately 2M solution of thioacetamide in acetonitrile. The yields for variations of 6. The method of Claim 1 wherein said polymer-sup- this reaction are reported below. The yield is reported ported amine catalyst is a macroreticular resin as a percent of the consumption of hydrogen sulfide in 10 bead. the reaction. Catalyst Time (h) Temp (°C) Yield Patentanspriiche Reilex®425 18 120 100 is 1. Verfahren zur Herstellung von Tioacetamid, umfas- Reilex®425 3 130 100 send das Inkontaktbringen von Acetonitril mit Reilly Poly-DMAP 2.25 120 100 Schwefelwasserstoff in Gegenwart einer kataly- tisch wirksamen Menge an Aminkatalysator auf Po- Each of these catalysts have been used in three lymertrager. consecutive reactions with no loss of effectiveness in 20 the present invention. It is expected that polymer-sup- 2. Verfahren nach Anspruch 1 , worin die Reaktion bei ported amine catalysts may be used many times in the einer Temperatur zwischen 100 und 150°C durch- present process without substantial loss of catalytic ef- gefuhrt wird. fectiveness. One use of the solution of thioacetamide in ace- 25 3. Verfahren nach Anspruch 2, worin die Reaktion bei tonitrile is in the preparation of thiazole or derivatives einer Temperatur zwischen 120 und 130°C durch- thereof. The following example demonstrates such a re- gefuhrt wird. action of thioacetamide and ethyl 4,4,4-trifluoro-2-chlo- roacetoacetate to produce ethyl 2-methyl-4-(trifluor- 4. Verfahren nach Anspruch 1, wobei Acetonitril im omethyl)thiazole-5-carboxylate, which may in turn be 30 molaren UberschuB zu Schwefelwasserstoff vor- used to produce fungicidal thiazolecarboxanilides. liegt. Example 2 5. Verfahren nach Anspruch 1 , wobei der Aminkataly- sator auf Polymertrager 4-Dimethylaminopyridin- Preparation of a Thiazole Derivative 35 gruppen, die an einem Polymerruckgrat hangen, umfaBt. A solution of thioacetamide in acetonitrile (6.66 mol), prepared as in Example 1, is placed in a flask. 6. Verfahren nach Anspruch 1, wobei dieser Aminka- Ethyl 2-chloro-4,4,4-trifluoroacetoacetate (5.06 mol) is talysator auf Polymertrager ein makroretikulares added and an exotherm is observed.
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