MXPA99008292A - An improved procedure for the conversion de2- (metiltio) -5- (trifluoromethyl) -1,3,4-tiadiazol (tda)) in 2- (metilsulfonil) -5- (trifluoromethyl) -1,3,4-tiadiazol ( tda sulfo - Google Patents
An improved procedure for the conversion de2- (metiltio) -5- (trifluoromethyl) -1,3,4-tiadiazol (tda)) in 2- (metilsulfonil) -5- (trifluoromethyl) -1,3,4-tiadiazol ( tda sulfoInfo
- Publication number
- MXPA99008292A MXPA99008292A MXPA/A/1999/008292A MX9908292A MXPA99008292A MX PA99008292 A MXPA99008292 A MX PA99008292A MX 9908292 A MX9908292 A MX 9908292A MX PA99008292 A MXPA99008292 A MX PA99008292A
- Authority
- MX
- Mexico
- Prior art keywords
- trifluoromethyl
- thiadiazole
- methylthio
- tda
- molar ratio
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 26
- 125000002023 trifluoromethyl group Chemical group FC(F)(F)* 0.000 title claims description 14
- 238000006243 chemical reaction Methods 0.000 title description 8
- 125000000020 sulfo group Chemical group O=S(=O)([*])O[H] 0.000 title 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-N acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229960000583 Acetic Acid Drugs 0.000 claims abstract description 22
- 239000003054 catalyst Substances 0.000 claims abstract description 22
- XMVONEAAOPAGAO-UHFFFAOYSA-N Sodium tungstate Chemical compound [Na+].[Na+].[O-][W]([O-])(=O)=O XMVONEAAOPAGAO-UHFFFAOYSA-N 0.000 claims abstract description 21
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 21
- 239000010937 tungsten Substances 0.000 claims abstract description 21
- 239000012362 glacial acetic acid Substances 0.000 claims abstract description 19
- AAQNGTNRWPXMPB-UHFFFAOYSA-N dipotassium;dioxido(dioxo)tungsten Chemical compound [K+].[K+].[O-][W]([O-])(=O)=O AAQNGTNRWPXMPB-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 14
- 239000002253 acid Substances 0.000 claims abstract description 11
- 239000007800 oxidant agent Substances 0.000 claims abstract description 11
- 230000003647 oxidation Effects 0.000 claims abstract description 11
- SQLPTSMJAQPVKR-UHFFFAOYSA-N 2-methylsulfonyl-5-(trifluoromethyl)-1,3,4-thiadiazole Chemical compound CS(=O)(=O)C1=NN=C(C(F)(F)F)S1 SQLPTSMJAQPVKR-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- 230000003197 catalytic Effects 0.000 claims abstract description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 36
- ULROOIOMHZXHRY-UHFFFAOYSA-N 2-methylsulfanyl-5-(trifluoromethyl)-1,3,4-thiadiazole Chemical compound CSC1=NN=C(C(F)(F)F)S1 ULROOIOMHZXHRY-UHFFFAOYSA-N 0.000 claims description 23
- CMPGARWFYBADJI-UHFFFAOYSA-L Tungstic acid Chemical compound O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 claims description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N toluene Substances CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 21
- 239000002904 solvent Substances 0.000 claims description 15
- 239000011541 reaction mixture Substances 0.000 claims description 13
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 125000002816 methylsulfanyl group Chemical group [H]C([H])([H])S[*] 0.000 claims description 9
- 239000007795 chemical reaction product Substances 0.000 claims description 8
- 230000001590 oxidative Effects 0.000 claims description 6
- 238000007792 addition Methods 0.000 claims description 4
- 125000003944 tolyl group Chemical group 0.000 claims description 3
- 239000000010 aprotic solvent Substances 0.000 claims description 2
- 125000003118 aryl group Chemical group 0.000 claims description 2
- 238000010533 azeotropic distillation Methods 0.000 claims description 2
- 238000002955 isolation Methods 0.000 claims description 2
- 125000004170 methylsulfonyl group Chemical group [H]C([H])([H])S(*)(=O)=O 0.000 claims description 2
- FNHWFALBBBUBGY-UHFFFAOYSA-N 4-tert-butyl-1,3-thiazole Chemical compound CC(C)(C)C1=CSC=N1 FNHWFALBBBUBGY-UHFFFAOYSA-N 0.000 claims 1
- -1 thiadiazole sulfones Chemical class 0.000 abstract description 15
- 239000000203 mixture Substances 0.000 abstract description 4
- UGUHFDPGDQDVGX-UHFFFAOYSA-N 1,2,3-thiadiazole Chemical compound C1=CSN=N1 UGUHFDPGDQDVGX-UHFFFAOYSA-N 0.000 description 29
- 150000003457 sulfones Chemical class 0.000 description 9
- DTQVDTLACAAQTR-UHFFFAOYSA-N trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 8
- YMWUJEATGCHHMB-UHFFFAOYSA-N methylene dichloride Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 4
- 238000009835 boiling Methods 0.000 description 3
- 239000000543 intermediate Substances 0.000 description 3
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 3
- VZJVWSHVAAUDKD-UHFFFAOYSA-N Potassium permanganate Chemical compound [K+].[O-][Mn](=O)(=O)=O VZJVWSHVAAUDKD-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000005712 crystallization Effects 0.000 description 2
- 150000002751 molybdenum Chemical class 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 230000002194 synthesizing Effects 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- 150000003658 tungsten compounds Chemical class 0.000 description 2
- IUVACELPFXBLHY-UHFFFAOYSA-N 2,5-bis(methylsulfanyl)-1,3,4-thiadiazole Chemical compound CSC1=NN=C(SC)S1 IUVACELPFXBLHY-UHFFFAOYSA-N 0.000 description 1
- WETWJCDKMRHUPV-UHFFFAOYSA-N Acetyl chloride Chemical compound CC(Cl)=O WETWJCDKMRHUPV-UHFFFAOYSA-N 0.000 description 1
- LUJVUUWNAPIQQI-QAGGRKNESA-N Boldione Chemical compound O=C1C=C[C@]2(C)[C@H]3CC[C@](C)(C(CC4)=O)[C@@H]4[C@@H]3CCC2=C1 LUJVUUWNAPIQQI-QAGGRKNESA-N 0.000 description 1
- RWGFKTVRMDUZSP-UHFFFAOYSA-N Cumene Chemical compound CC(C)C1=CC=CC=C1 RWGFKTVRMDUZSP-UHFFFAOYSA-N 0.000 description 1
- MQJKPEGWNLWLTK-UHFFFAOYSA-N Di(p-aminophenyl)sulphone Chemical compound C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=C1 MQJKPEGWNLWLTK-UHFFFAOYSA-N 0.000 description 1
- VLAPMBHFAWRUQP-UHFFFAOYSA-L Molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 1
- 102000014961 Protein Precursors Human genes 0.000 description 1
- 108010078762 Protein Precursors Proteins 0.000 description 1
- 230000002378 acidificating Effects 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 125000004390 alkyl sulfonyl group Chemical group 0.000 description 1
- 230000000843 anti-fungal Effects 0.000 description 1
- 239000003849 aromatic solvent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 125000002534 ethynyl group Chemical class [H]C#C* 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000002363 herbicidal Effects 0.000 description 1
- 239000004009 herbicide Substances 0.000 description 1
- AUHZEENZYGFFBQ-UHFFFAOYSA-N mesitylene Substances CC1=CC(C)=CC(C)=C1 AUHZEENZYGFFBQ-UHFFFAOYSA-N 0.000 description 1
- 125000001827 mesitylenyl group Chemical group [H]C1=C(C(*)=C(C([H])=C1C([H])([H])[H])C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N o-xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- 150000004291 polyenes Polymers 0.000 description 1
- OZAIFHULBGXAKX-UHFFFAOYSA-N precursor Substances N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 150000003455 sulfinic acids Chemical class 0.000 description 1
- 125000000472 sulfonyl group Chemical group *S(*)(=O)=O 0.000 description 1
- 150000003461 sulfonyl halides Chemical class 0.000 description 1
- 150000004867 thiadiazoles Chemical group 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Abstract
The present invention relates to a process for preparing thiadiazole sulfones. Specifically, the present process is used to prepare 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-thiadiazol employing catalytic oxidation in the presence of a suitable oxidizing agent. The catalyst system used for the oxidation reaction is a mixture of glacial acetic acid and a tungsten catalyst. The tungsten catalyst is preferably selected from the group consisting of sodium tungstate, potassium tungstate and túngsti acid.
Description
AN IMPROVED PROCEDURE FOR THE CONVERSION OF 2 - (METHYLTHY) -5- (TRIFLUOROMETHYL) -1,3,4-TIADIAZOL (TDA) IN 2- (METILSULFONIL) -5- (TRIFLUOROMETHYL) -1,3,4-TIADIAZOL ( TDA SULFONA)
TECHNICAL FIELD OF THE INVENTION The field of the present invention is the synthesis of thiadiazole sulfones. More specifically, the present invention relates to an improved process for converting 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole (TDA) to 2- (methylsulfonyl) -5- (trifluoromethyl) -1 , 3,4-thiadiazole (TDA sulfone).
BACKGROUND OF THE INVENTION
The sulfones have the general structure RR'S02. The sulfones can be produced from a variety of precursors. For example, sulfones can be prepared by (a) oxidizing sulfides, (b) redistribution of sulfuric esters, (c) addition of sulfonyl halides to alkenes and acetylenes, (d) addition of sulfinic acids to polarized bonds and (e) ) addition of S02 to polyenes (see, for example, Durst, T., in Comprehensive Organic Chemistry: Chapter 11.6, Barton and Ollis, Eds., Pergamon Press, Oxford, 1979). A particular class of sulfones, 2- (alkylsulfonyl) -5- (trifluoromethyl) -1,3,4-thiadiazoles, are intermediates used in the production of herbicides. It has been reported that a particular sulfone within this class, 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-thia-diazole, possesses antifungal activity (see US Patent 3,562,284) . According to U.S. Pat. 3,562,284, the 2- (substituted sulfonyl) -5- (trifluoromethyl) -1, 3, -thiadia-zoles can be prepared by oxidizing a corresponding 2- (substituted thio) -5- (trifluoromethyl) -1, 3, 4 -thiadiazole in the presence of an oxidizing agent, such as potassium permanganate, hydrogen peroxide or peroxytrifluoroacetic acid. The oxidation takes place in an acidic aqueous medium, which includes acetic acid and methylene chloride as the solvent. Methylene chloride is an undesirable solvent from the point of view of hygiene and industrial handling. Handling is difficult due to its low boiling point (high vapor pressure). In addition, it contaminates the aqueous streams. The sulfone product is isolated using crystallization. The described yield of the sulfone, based on the starting sulfide, is approximately 65%. In this known process, the use of acetic acid in the presence of water introduces excess water into the reaction and requires purification of the sulfone using expensive crystallization processes, with resulting low yields. Therefore, there remains a need in the art for a practical and inexpensive procedure for preparing thiadiazole sulfones with a high yield.
BRIEF COMPENDIUM OF THE INVENTION
The present invention provides a process for preparing 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-thiadiazole, consisting of oxidizing 2- (methylthio) -5- (trifluoromethyl) -1, 3, 4 -thiadiazole in a reaction mixture containing glacial acetic acid and a catalytic amount of a tungsten catalyst to form a reaction product. The tungsten catalyst includes any tungsten compound (as opposed to elemental tungsten) that can form pertúngstico acid, - or the tungsten catalyst can be the same tungstic acid. The pertúngstico acid is the intermediate acid formed when the hydrogen peroxide reacts with túngstico acid. Tungstic acid can be formed by the reaction of sodium tungstate or potassium tungstate with sulfuric acid. In a preferred embodiment, the tungsten catalyst is selected from the group consisting of sodium tungstate, potassium tungstate and tungstic acid. A preferred oxidizing agent is hydrogen peroxide. According to this embodiment, 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole reacts with hydrogen peroxide in the presence of glacial acetic acid and either sodium tungstate, or potassium tungstate or tungstic acid. The hydrogen peroxide used in the reaction mixture is preferably an aqueous solution containing from about 30 weight percent to about 50 weight percent hydrogen peroxide. Hydrogen peroxide is present in a molar excess relative to 2- (methylthio) -5- (trifluoromethyl) -1, 3 -4-thiadiazole. Preferably, the molar ratio of hydrogen peroxide to 2- (methylthio) -5- (trifluoromethyl) -1, 3-4-thiadiazoles from about 2.0: 1 to about 3.0: 1. Even more preferably, the molar ratio is from about 2.05: 1 to about 2.5: 1. Glacial acetic acid is present in an amount of about 0.1 moles to about 0.5 moles of acetic acid per mole of 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole. More preferably, the molar ratio of glacial acetic acid to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.2: 1 to about 0.3: 1. In a preferred embodiment, the sodium tungstate is present in an amount of about 0.001 mole to about 0.025 mole of sodium tungstate per mole of 2- (methylthio) -5- (trifluoromethyl) -1, 3-4-thiadiazole. More preferably, the mole ratio of sodium tungstate to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.002: 1 to about 0.008: 1. In another preferred embodiment, the potassium tungstate is present in an amount of about 0.001 mole to about 0.025 mole of potassium tungstate per mole of 2- (methylthio) -5- (trifluoromethyl) -1, 3 -4-thiadiazole. More preferably, the molar ratio of potassium tungstate to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.002: 1 to about 0.008: 1. In yet another preferred embodiment, the tungstic acid is present in an amount of about 0.001 mole to about 0.025 mole of tungstic acid per mole of 2- (methylthio) -5- (trifluoromethyl) -1, 3-4-thiadiazole. Preferably, the molar ratio of tungstic acid to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadia-zol is from about 0.002: 1 to about 0.008: 1. Oxidation typically occurs at a temperature of about 60 ° C to about 110 ° C and, preferably, at a temperature of about 70 ° C to about 100 ° C. The method of the present invention may include additional steps. Sulfuric acid can be added to the reaction mixture to acidify the mixture. Also I know
can remove water from the reaction product. The removal of water is preferably performed azeotropically. Still further, an embodiment of this invention may include the step of isolating 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-thiadiazole formed. 0 In Patent Application No. 08 / 989,568, there is disclosed a process for preparing 2- (methylsulfo-nyl) -5- (trifluoromethyl) -1,3,4-thiadiazole by oxidizing 2- (methylthio) -5- ( trifluoromethyl) -1,4,4-thiadiazole in a reaction mixture containing activated molybdenum or tungsten catalyst. The activated molybdenum or tungsten catalyst in the invention is molybdic acid or tungstic acid, respectively. The reaction of the process is carried out in the absence of glacial acetic acid. In Patent Application No. 08 / 989,594, a process is described for preparing 2- (methylthio) -5- (trifluoromethyl) -1,3-thiadiazole by oxidizing 2- (methylthio) -5- (trifluoromethyl) -1, 3,4-thiadiazole in the presence of a glacial acetic acid catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for producing thiadiazole sulfones. The present procedure is used to prepare 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3-thiadiazole (TDA sulfone) from 2- (methylthio) -5- (trifluoromethyl) -1, 3-4- thiadiazole (TDA). The TDA sulfone is prepared using catalytic oxidation of the TDA in the presence of a suitable oxidizing agent. The catalysts used for the oxidation reaction are glacial acetic acid and a tungsten catalyst. The tungsten catalyst includes any tungsten compound (as opposed to elemental tungsten) that is capable of forming pertúngstico acid, or the tungsten catalyst can be the same tungstic acid. The pertúngstico acid is the intermediate acid formed when the hydrogen peroxide reacts with túngstico acid. Tungstic acid can be formed by the reaction of sodium tungstate or potassium tungstate with sulfuric acid. Preferred tungsten catalysts include sodium tungstate, potassium tungstate and tungstic acid. The process of the invention includes the step of oxidation of 2- (methylthio) -5- (trifluoromethyl) -1,3-, 4-thiadiazole (TDA) in a reaction mixture containing glacial acetic acid and a tungsten catalyst to form a reaction product containing the TDA sulfone. Oxidation of the TDA takes place in the presence of a suitable oxidizing agent. Examples of such oxidation agents are well known in the art (see, for example, Durst, T., in Comprehensive Organic Chemistry: Chapter 11.6, Barton and Ollis, Eds., Pergamon Press, Oxford (1979)). A preferred oxidizing agent is hydrogen peroxide (H202). According to this embodiment, the TDA reacts with hydrogen peroxide in the presence of glacial acetic acid and (1) sodium tungstate or (ii) potassium tungstate or (iii) tungstic acid. The hydrogen peroxide used in the reaction mixture is preferably an aqueous solution containing from about 30 weight percent to about 50 weight percent hydrogen peroxide. The molar ratio of H20 to TDA is from about 2.0: 1 to about 3.0: 1 and, preferably, from about 2.05: 1 to about 2.5: 1. Oxidation conditions are well known in the art. Typically, the oxidation is carried out at a temperature of about 60 ° C to about 110 ° C and, preferably, at a temperature of about 70 ° C to about 100 ° C. The TDA used in the present procedure can be obtained from any source. Preferably, the TDA is prepared by a process that provides TDA in an aprotic aromatic solvent, such as toluene. Especially preferred means for preparing TDA can be found in US Patent Applications. titrated "A procedure for preparing 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole using methyl dithiocarbazinate and trifluoroacetic acid" (Serial No. 08 / 989,152, filed 12/12/97) , "A method for preparing 2- (methylthio) -5- (trifluoromethyl) -1,3-, 4-thiadiazole using methyl dithiocarbazinate with trifluoroacetic acid with selective removal of 2,5-bis (methylthio) -1,3,4 -thiadiazole "(Serial #)
08 / 989,553, filed 12/12/97) and "A procedure for preparing 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole using methyl dithiocarbazinate and a molar excess of trifluoroacetic acid with recovery of trifluoroacetic acid "(Series No. 08 / 989,485, filed on 12/12/98). The descriptions of the three applications are all here incorporated by way of reference. Oxidation of the TDA occurs in the presence of a solvent. Preferably, the solvent is an aromatic aprotic solvent. Such solvents are well known in the art. Preferred examples of such solvents are toluene, xylene, cumene and mesitylene. Toluene is especially preferred. The amount of solvent used can vary over a wide range, as will be readily determined by one skilled in the art. The precise amount of solvent will depend on the particular solvent used. When the solvent is toluene, it is present in an amount of about 0.5 moles to about 3.5 moles of toluene per mole of TDA. Preferably, the toluene is present in an amount of about 1.0 mole to about 2.0 mole per mole of TDA and, more preferably, in an amount of about 1.0 mole to about 1.5 mole of toluene per mole of TDA The TDA is oxidized in a reaction mixture containing glacial acetic acid and a tungsten catalyst preferably selected from the group consisting of sodium tungstate, potassium tungstate and tungstic acid, to form a reaction product containing TDA sulfone. The sources of ADT, the use of a solvent, the reaction conditions and the choice of suitable oxidizing agents are the same as those indicated above. The oxidizing agent (e.g., hydrogen peroxide) used in the reaction mixture is preferably present in a molar excess relative to the TDA. Preferably, the molar ratio of oxidizing agent to TDA is from about 2.0: 1 to about 3.0: 1. Even more preferably, the ratio is from about 2.05: 1 to about 2.5: 1. The glacial acetic acid and either the sodium tungstate or the potassium tungstate or the tungstic acid are directly added to the reaction mixture. Glacial acetic acid is present in an amount of about 0.1 moles to about 0.5 moles of acetic acid per mole of TDA. Preferably, the molar ratio of glacial acetic acid to TDA is from about 0.2: 1 to about 0.3: 1. In a preferred embodiment, the sodium tungstate is present in an amount of about 0.001 mole to about 0.025 mole of sodium tungstate per mole of TDA. Preferably, the molar ratio of sodium tungstate to TDA is from about 0.002: 1 to about 0.008: 1. In another preferred embodiment, the potassium tungstate is present in an amount of about 0.001 mole to about 0.025 mole of potassium tungstate per mole of TDA. Preferably, the molar ratio of potassium tungstate to TDA is from about 0.002: 1 to about 0.008: 1. In yet another preferred embodiment, the tungstic acid is present in an amount of about 0.001 mole to about 0.025 mole of tungstic acid per mole of TDA. Preferably, the molar ratio of tungstic acid to TDA is from about 0.002: 1 to about 0.008: 1.
In one embodiment of the present invention, sulfuric acid may be added in an amount less than, or equal to, about 0.5 moles to the reaction mixture to acidify the mixture. In addition, water can be removed from the reaction product. Still further, a method of this invention may include the isolation step of the formed sulfone. The removal of water is preferably carried out azeotropically. The azeotropic removal of water is easily carried out in the presence of the solvent, particularly when the solvent is toluene. Since the azeotrope has a lower boiling point than water, the heating of the reaction product to the boiling point of the solvent effectively removes the water. As the oxidation reaction occurs in the range of about 60 ° C to about 110 ° C, the water is removed during that reaction; no additional stage is required. The following Example illustrates a preferred embodiment of the present invention and is not limiting of the specification or the claims.
EXAMPLE Synthesis of TDA sulfone using glacial acetic acid and sodium tungstate 1.5 mol of TDA in toluene, approximately 0.33 mol of glacial acetic acid, approximately 0.0065 mol of sodium tungstate and approximately 0.027 were charged to a reactor vessel. moles of sulfuric acid. The reaction mixture was then heated to a temperature of about 80 ° C to 85 ° C and 3.65 moles of 35% hydrogen peroxide were added over a period of about 4 hours- heated the resulting mixture over a period of about 7 hours and the water was removed azeotropically. The average yield of TDA sulfone was approximately 99.4%, based on the TDA used in the procedure.
Although the invention has been described in detail in the foregoing for illustrative purposes, it should be understood that said detail has only that purpose and that those skilled in the art can make variations therein without departing from the spirit and scope of the invention, except as may be limited by the claims.
Claims (22)
1. A process for preparing 2- (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-thiadiazole consisting of oxidizing 2- (methylthio) -5- (trifluoromethyl) -1,3-, 4-thiadiazole in a reaction mixture which contains an oxidizing agent, glacial acetic acid and a catalytic amount of a tungsten catalyst, which is tungstic acid or which is capable of forming pertúngstico acid, to form a reaction product, where the molar ratio of glacial acetic acid to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiazole is from about 0.1: 1 to about 0.5: 1.
2. The process of Claim 1, wherein the tungsten catalyst is selected from the group consisting of sodium tungstate, potassium tungstate and tungstic acid.
3. The process of Claim 2, wherein the tungsten catalyst is sodium tungstate.
4. The method of Claim 2, wherein the tungsten catalyst is potassium tungstate.
5. The process of Claim 2, wherein the tungsten catalyst is tungstic acid.
6. the process of Claim 3, wherein the molar ratio of sodium tungstate to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.001: 1 to about 0.025: 1.
7. The process of Claim 4, wherein the molar ratio of potassium tungstate to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.001: 1 to about 0.025: 1.
8. The method of Claim 5, wherein the molar ratio of tungstic acid to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.001: 1 to about 0.025: 1.
9. The method of Claim 1, wherein the oxidizing agent is hydrogen peroxide.
10. The process of Claim 1, wherein 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is dissolved in an aromatic aprotic solvent.
11. The process of Claim 10, wherein the solvent is toluene.
12. The method of Claim 11, wherein the I.1 molar ratio of toluene to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.5: 1 to about 3.5: 1.
13. The process of Claim 12, wherein the: molar ratio of toluene to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 1: 1 to about 1.5: 1.
14. The process of Claim 1, wherein the oxidation takes place at a temperature of about 60 ° C to about 110 ° C.
15. The method of Claim 14, wherein the temperature is from about 70 ° C to about 100 ° C.
16. The method of Claim 9, wherein the molar ratio of hydrogen peroxide to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 2.0: 1 to about 3.0: 1. .
17. The method of Claim 16, wherein the molar ratio of hydrogen peroxide to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 2.05: 1 to about 2.50: 1. .
18. The method of Claim 1, wherein the molar ratio of glacial acetic acid to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.2: 1 to about 0.3: 1. .
19. The method of Claim 6, wherein the molar ratio of sodium tungstate to 2- (methylthio) -5- (trifluoromethyl) -1,3,4-thiadiazole is from about 0.002: 1 to about 0.008: 1.
20. The method of Claim 1, further including the azeotropic removal of water from the reaction product.
21. The method of Claim 1, which further includes the isolation of del-2 - (methylsulfonyl) -5- (trifluoromethyl) -1,3,4-diazodiazole.
22. The method of Claim 1, further including the addition of less than or equal to about 0.5 moles of sulfuric acid to the reaction mixture.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08153920 | 1993-11-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| MXPA99008292A true MXPA99008292A (en) | 2000-06-05 |
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