GB2154232A - Process for the preparation of 2-aminothiophenes - Google Patents
Process for the preparation of 2-aminothiophenes Download PDFInfo
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- GB2154232A GB2154232A GB08403869A GB8403869A GB2154232A GB 2154232 A GB2154232 A GB 2154232A GB 08403869 A GB08403869 A GB 08403869A GB 8403869 A GB8403869 A GB 8403869A GB 2154232 A GB2154232 A GB 2154232A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D409/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms
- C07D409/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms containing two hetero rings
- C07D409/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms containing two hetero rings directly linked by a ring-member-to-ring-member bond
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D413/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms
- C07D413/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings
- C07D413/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings directly linked by a ring-member-to-ring-member bond
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D417/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00
- C07D417/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00 containing two hetero rings
- C07D417/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00 containing two hetero rings directly linked by a ring-member-to-ring-member bond
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D421/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having selenium, tellurium, or halogen atoms as ring hetero atoms
- C07D421/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having selenium, tellurium, or halogen atoms as ring hetero atoms containing two hetero rings
- C07D421/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having selenium, tellurium, or halogen atoms as ring hetero atoms containing two hetero rings directly linked by a ring-member-to-ring-member bond
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- Organic Chemistry (AREA)
- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
- Plural Heterocyclic Compounds (AREA)
Abstract
Thiophenes of the formula <IMAGE> wherein R<1> is an electron withdrawing group and R<2> and R<3> are each selected from H, alkyl, cycloalkyl, aryl and the R<1> groups, are prepared by contacting a reactant of the formula <IMAGE> wherein <9>R and R<10> are, for example, alkyl or aryl, with a reactant of the formula R<1>-CH301 in the presence of a base for a sufficient period to produce the intermediate of the formula <IMAGE> and thereafter contacting said intermediate with sulfur for a sufficient period to cyclize said intermediate to the thiophene.
Description
SPECIFICATION
Process for the preparation of 2-aminothiophenes
This invention relates to the preparation of 2-aminothiophenes which are particularly useful as intermediates for the preparation of azo dyes, some of which are as disclosed, for example, in U.S. Patent 4,400,318.
The 2-aminothiophenes of concern have the general structure
wherein:
R1 is an electron withdrawing group preferably selected from: the heterocyclic radicals
wherein the substituents R4-R7 are independently selected from H, -NO2, -CN, halogen, alkyl, cycloalkyl, alkoxy, -COOalkyl, -OOCalkyl, -CHO, and -COalkyl; -CN; -NO2; -CO2R; -CON(R)2; -SO3R; -SO2R; -SO2N(R)2; where R is H, alkyl, cycloalkyl, or aryl; and R8CO-, where R8 is H, alkyl, cycloalkyl, aryl, or any of the above heterocyclic radicals;
R2 and R3 are each selected from H, alkyl, cycloalkyl, aryl, and the above R1 substituents;
and wherein the alkyl groups and alkyl or alkylene segments or moieties, e.g., the alkyl of the alkoxy groups, within the above definitions of R1, R2 and R3 are straight or branched chain of 1-6 carbons and are unsubstituted or substituted with 1-3 of alkoxy, hydroxy, halogen, -CN, -SO2alkyl, -SO2Ph, -OOCalkyl, -COQalkyl, -CONH2, -CONHalkyl, -CON(alkyl)2, -S-alkyl, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2, -S-Ph, -O-Ph, or Ph.
Routes to 2-aminothiophenes have been developed, based on the chemistry of K. Gewald, Chem. Ber. 98, 3571 (1965) wherein an a-mercapto aldehyde is condensed with a reactive methylene nitrile. This method, however, has limitations regarding the variety of substituents which readily can be placed on the thiophene, particularly in the 5-position. Moreover, the yields and assays tend to be low, particularly with the more desirable substituents, such as the heterocyclic radicals shown above.
The present process particularly concerns the preparation of 2-aminothiophenes containing electron withdrawing groups in the 5- and/or 3-positions, uniquely employing either of the reactant species
in combination with the reactant R1-CH3, as opposedtothe R7 substituent being on eitherthe a-mercaptoaldehyde or the enamine analogue of the aldehyde. This unique combination of reactants allows a wider range of R1 substituents, results in much improved yields and assays of the 2-aminothiophenes, and allows a greater selection of solvents for obtaining optimum yield and purity of specific 2-aminothiophene products.
In the above reactants, R9 is alkyl as defined above, cycloaklyl or aryl, preferably alkyl, and each R15 is selected from alkyl as defined above, cycloalkyl, aryl, fCH2+5r and tCH2)20(CH2t2, preferably alkyl or tCH2ts.
The present process is depicted below employing the enamine analogue of the aldehyde as the exemplary reactant species:
In the process, the enamine (I) of a reactive methylene nitrile condenses with an activated methyl compound (II) in the presence of base (B:), in unexpectedly high yield. The condensation product (lil), which can be considered to exist in two tautomericforms, subsequently reacts with sulphur, resulting in a spontaneous cyclisation to give the substituted 2-aminothiophene (IV) in high yield.
The process can be carried out in two stages or combined in a 'one pot' synthesis. The former gives the advantage of a choice of solvents for the second stage such that the optimum yield and purity of the substituted 2-aminothiophene may be obtained.
The present invention is defines as the process for preparing thiophenes of the formula
wherein R1 is an electron withdrawing group, and R2 and R3 are each selected from H, alkyl, cycloalkyl, aryl and the R1 substituents, comprising contacting a reactant of the formula
wherein R9 is alkyl, cycloaklyl or aryl, or
wherein R10 is alkyl, cycloalkyl, aryl,tCH245 or bCH2)2O(CH2t2 with a reactant of the formula R1-CH3 in the presence of a base for a sufficient period to produce the intermediate of the formula
and thereafter contacting said intermediate with sulfur four a sufficient period to cyclize said intermediate to the thiophene.For this process, the most preferred R1 groups or radicals are selected from 2-benzothiazolyl, 2-benzoxazolyl, alkanoyl, aroyl, and 2-thienoyl, each of which may be substituted with 1-3 substituents independently selected from -NO2, -CN, halogen, alkyl, cycloalkyl, alkoxy, -COOalkyI, -OOCalkyl, -CHO, and -COalkyl, and the most preferred R2 and R3 groups are independently selected from -CO2R, -CN, -COR, -SO2R, and -CON H2.
In carrying out the present process, the reaction temperature, solvent, base, order of reaction addition and the like can be widely varied. The temperature can range from about 10 C. to about 100"C. depending on the heat stability, compatability, solubility and the like of the reactants with respect, for example, to the particular solvent system and base. A variety of solvents can be employed including N,N-dimethyl formamide (DMF), methanol, ethanol, isopropanol, and water. Also, a variety of bases can be used, including sodium methoxide, ethoxide or t-butoxide, piperidine, morpholine, and triethylamine.
In the process wherein the reactant species is
the reaction conditions are similar to those for (C) as shown in Example 1 below and preferably are as follows: The reactant in DMF, and the active methyl compound II are added to a solution of base in DMF. The system is heated for about two hours at about 60"C., a further portion of base, in DMF, is then added, and heating then continued for an additional hour at about 60"C. Product is obtained by cooling, treating with HCI, filtering and washing. The product is then reacted with sulphur.
The reactant species
(A) may be prepared by the method analogous to that outlined by Reuben G. Jones (JACS 73 3684 (1951) from the corresponding 'B' compound and cupric acetate,
(B) may be prepared from trialkyl orthoformate and alkylcyanoacetate by the method outlined by Reuben G.Jones (JACS74; 4889 (1952)), and
(C) may be prepared in quantitative yield by the spontaneous reaction of (B) with a secondary amine.
The invention can be further understood by reference to the following specific examples which are not intended to limit the invention, but merely to illustrate the same.
EXAMPLE 1
Preparation of2-Amino-3-Carbomethoxy-5Benzoxazolyl Thiophene 1 -Carbomethoxy-1 -cyano-2-(N,N-dimethylamino)-ethene (1.5g,0.0097 mole) and 2-methyl benzoxazole (1.3 g, 0.0098 mole) in N,N-dimethyl formamide (5 cm3) was added to a solution of potassium-t. butoxide (1.1 g, 0.0098 mole) in N,N-dimethyl formamide (5 cm3), over 15 minutes. The resultant mixture was stirred at 20"C. for two hours. Sulphur (0.3g, 0.0094 gram atom) was added and the mixture heated at 50-60"C. for two hours. The product obtained on cooling was filtered and washed with water. This resulted in 1.0 g (37.2% of theory) of 2-amino-3-carbomethoxy-5-benzoxazolyl-thiophene.By comparison, 2.8% of theory of 2-amino-3carbomethoxy-5-benzoxazolythiophene was obtained by a prior art method.
EXAMPLE 2
Preparation of 1- Carbomethoxy- 1-Cyano-3-Benzothiazolyl- 1,2-propene Potassium t-butoxide (11.2 g, 0.1 mole) was dissolved in N,N-dimethyl formamide (50 cm3) at 20"C. A solution of 2-methyl benzothiazole (14.9 g, 0.1 mole) and 1-cyano-1 -carbomethoxy-2-piperidinoethene (19.4 g, 0.1 mole) in N,N-dimethyl formamide (100 cm3) was added over about 30 minutes, controlling the temperature at 50-60"C.
The resultant solution was heated at 60"C. for two hours. A further portion of potassium-t. butoxide (11.2 g, 0.1 mole) was added and the solution stirred for a further hour at 60"C. Thin layer chromatography indicated completion of reaction.
The reaction mixture was added, dropwise, to 10% hydrochloric acid (200 cm3) and the resultant yellow precipitate collected and washed well with water. This method yielded 23.3 g (90.5% of theory) of 1 -carbomethoxy-1 -cyano-3-benzothiazolyl-1 ,2-propene, which assayed at 94% by high performance liquid chromatography.
EXAMPLE 3
Preparation of2-Amino-3-Carbomethoxy-5-Benzothiazolyl Thiophene 1-Carbomethoxy-1-cyano-3-benzothiazolyl-1,2-propene (0.516 g) 0.002 moles) was slurried in propan-2-ol (4 cm3). Piperidine (0.34 g, 0.004 moles) was added resulting in a yellow solution. Sulphur (0.064 g, 0.002 gram atom) was added and the mixture heated at reflux for 30 minutes. Thin layer chromatography indicated completion of reaction. The solution was cooled to 20"C. and the resultant yellow crystals collected and washed with propan-2-ol and water. This method yielded 0.42 g (72.4% of theory) of 2-amino-3carbomethoxy-5-benzothiazolyl-thiophene, which assayed at 99% by high performance liquid chromatography.This method compares with a yield of 15% of theory of 2-amino-3-carbomethoxy-5-benzothiazolyl thiophene by a prior art method.
EXAMPLE 4
Preparation of 1-Carbomethoxy- 1-Cyano-3-Benzoxazolyl- 1,2-Propene
Potassium t- butoxide (5.6 g 0.05 mole) was dissolved in N,N-dimethyl formamide (25 cm3) at 20"C. A solution of 2-methyl benzoxazole (6.65 g, 0.05 mole) and 1-cyano-1-carbomethoxy-2-piperidinoethene (9.7 g, 0.05 mole) in N,N-dimethyl formamide (50 cm3) was added over about 30 minutes, controlling the temperature at 50-60"C.
The resultant solution was heated at 60 C. for two hours. A further portion of potassium-t. butoxide (5.6 g, 0.05 mole) was added and the solution stirred for a further hour at 60"C. Thin layer chromatography indicated completion of reaction.
The reaction mixture was added, dropwise, to 10% hydrochloric acid (10 cm3) and the resultant pale yellow precipitate collected and washed well with water. This method yielded 11.3 g (93.4% of theory) of 1 -carbomethoxy-1 -cyano-3-benzoxazolyl-1 ,2-propene.
EXAMPLE 5 Preparation of mino-3- Carbomethoxy-5-Renzoxazolyl- Thiophene 1-Carbomethoxyl-1-cyano-3-benzoxazolyl-1,2-propene (0.516 g, 0.002 moles) was slurried in propan-2-ol (4 cm3). Piperidine (0.34 g, 0.004 moles) was added resulting in a yellow solution. Sulphur (0.064 g, 0.002 gram atom) was added and the mixture heated at reflux for 30 minutes. Thin layer chromatography indicated completion of reaction. The solution was cooled to 209C. and the resultant yellow crystals collected and washed with propan-2-ol and water. This method yielded 0.32 g (58.4% of theory) of 2-amino-3carbomethoxy-5-benzoxazolyl-thiophene, which assayed at 99% by high performance liquid chromatography.By comparison, 2.8% of theory of 2-amino-3-carbomethoxy-5-benzoxazolyl-thiophene was obtained by a prior art method.
EXAMPLE 6
2-Amino-3-carboethoxy-5-isobutyryl thiophene was obtained from 3-methyl-butan-2-one and 2 carboethoxy-1-cyano-2-ethoxy-ethene by the method of Example 1.
EXAMPLE 7
2-Amino-3-carbomethoxy-5-thien-2-oyl-thiophene was obtained from 2-acetyl thiophene by the method of
Example 1.
EXAMPLE 8 1 -Carbomethoxy-1-cyano-3-benzoyl-1,2-propene was obtained from acetophenone by the method of
Example 2.
EXAMPLE 9
2-Amino-3-carbomethoxy-5-benzoyl thiophene was obtained from 1 -carbomethoxy-1 -cyano-3-benzoyl1,2-propene bythe method of Example 3.
EXAMPLE 10
2-Amino-3-carboethoxy-5-benzoyl thiophene was obtained from acetophenone by the method of Example 1.
EXAMPLE 11
2-Amino-3-cyano-5-benzoyl thiophene was obtained from acetophenone and 1,1 -dicyano-2-(N,Ndimethyl)-amino ethene by the method of Example 1.
EXAMPLE 12
This example illustrates the use
Sodium methoxide (1.1 g 0.02 mole) was suspended in DMF (10cm2) and a mixture of methylisopropyl ketone (1.5 cm3) and ethylethoxymethylene cyanoacetate (1.5 g, 0008 mole) was added dropwise. After 30 minutes, sulphur (0.32 g, 0.01 m) was added and the mixture heated at 800C. for one hour and then at 95"C.
for 2-1/2 hours. The mixture was cooled and water added to precipitate the product.
The following table gives specific exemplary compounds for
TABLE I
R1 R2 R3 R9 R10 .\ H -CO2CH2 H - -CH3 ik /il s v /N S CO2CH3 H ~ fCH2 ts h./ s -CO2CH3 H - +CH2t \ /.-co- CO2CH3 H - -CH3 \// )\.-Co -CO2CH3 H - -CH3 Cl- co- )\.-co -CN H - -CH3 CH3-.'-'-CO- -CO2CH3 H - -CH3 CH30-CO- -COC2H5 H .'\./Nha CH:'\/' s/ Cl-. .-CO- -CO2CH3 H s/ S .) ).-co -CN H - -CH3 .\ /.-co- CO2CH3 -Ph - -CH3 S rl H2 n -C2H5 \s/ CoNH2 H -C2H5
-SO2Ph H Ph / < -SO2CH3 H - CH2)2o(CH2+2 (CH3 )2CHCo- -S02C2H5 H #CH2+5
Claims (5)
1. The process for preparing thiophenes of the formula
wherein R1 is an electron withdrawing group and R2 and R3 are each selected from H, alkyl, cycloalkyl, aryl and the R1 groups, comprising contacting a reactant of the formula
wherein R9 is alkyl, cycloalkyl or aryl, or
wherein R10 is alkyl, cycloalkyl, aryl, CH2t5 or SCH2)20(CH2 t2, with a reactant of the formula R1-CH3 in the presence of a base for a sufficient period to produce the intermediate of the formula
and thereafter contacting said intermediate with sulfur for a sufficient period to cyclize said intermediate to the thiophene.
2. The process of Claim 1 wherein R1 is an electron withdrawing group selected from: the heterocyclic
radicals
wherein the substituents R4-R7 are independently selected from H, -NO2, -CN, halogen, alkyl, cycloalkyl, alkoxy, -COOalkyl, -OOCalkyl, -CHO, and -COalkyl; -CN; -NO2; -CO2R; -CON(R)2; -SO3R; -SO2R; -SO2N(R)2; where R is H, alkyl, cycloalkyl, or aryl; and R8CO-, where R8 is H, alkyl, cycloalkyl, aryl, or any of the above heterocyclic radicals;
R2 and R3 are each selected from H, alkyl, cycloalkyl, aryl, and the above R1 substituents;
and wherein the alkyl groups and alkyl or alkylene segments or moieties within the above definitions of R1,
R2 and R3 are straight or branched chain of 1-6 carbons and are unsubstituted or substituted with 1-3 of alkoxy, hydroxy, halogen, -CN, -SOpalkyl, -SO2Ph, -OOC- alkyl, -COOalkyl, -CONH2, -CONHalkyl, -CON- (alkyl)2, -S-alkyl, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2, -S-Ph, -O-Ph, or Ph.
3. The process of Claim 1 employing
wherein: R1 is
or (CH3)2CHCO-, wherein the rings may be substituted with 1-3 of alkyl, alkoxy, halogen or cyano; R2 is -CO2aIkyl, -CN, -CONH2, or -SO2alkyl; and R3 is H, alkyl or phenyl.
4. The process of Claim 1 employing
wherein: R1 is
or (CH2)2CHCO- ,wherein the rings may be substituted with 1-3 of alkyl, alkoxy, halogen or cyano; R2 is -CO2alkyl, -CN, -CONH2, or -SO2alkyl; R3 is H, alkyl or phenyl; and R9 is alkyl or phenyl.
5. The process of Claim 1 employing
wherein: R1 is wherein: R1 is
or (CH3)2CHCO- ,wherein the rings may be substituted with 1-3 of alkyl, alkoxy, halogen or cyano; R2 is -CO2alkyl, -CN, -CON H2, or SO2alkyl; R3 is H, alkyl or phenyl; and R10 is alkyl +CH2+5, or f CH2)2O(CH2+.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08403869A GB2154232B (en) | 1984-02-14 | 1984-02-14 | Process for the preparation of 2-aminothiophenes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08403869A GB2154232B (en) | 1984-02-14 | 1984-02-14 | Process for the preparation of 2-aminothiophenes |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8403869D0 GB8403869D0 (en) | 1984-03-21 |
| GB2154232A true GB2154232A (en) | 1985-09-04 |
| GB2154232B GB2154232B (en) | 1987-08-26 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08403869A Expired GB2154232B (en) | 1984-02-14 | 1984-02-14 | Process for the preparation of 2-aminothiophenes |
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| Country | Link |
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| GB (1) | GB2154232B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5201934A (en) * | 1989-10-07 | 1993-04-13 | Basf Aktiengesellschaft | Carboxamides and their use as herbicides |
-
1984
- 1984-02-14 GB GB08403869A patent/GB2154232B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5201934A (en) * | 1989-10-07 | 1993-04-13 | Basf Aktiengesellschaft | Carboxamides and their use as herbicides |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8403869D0 (en) | 1984-03-21 |
| GB2154232B (en) | 1987-08-26 |
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| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930214 |