Process for preparation of 2-aminothiazolecarboxamide...

Details Process for preparation of 2-aminothiazolecarboxamide... Process for preparation of 2-aminothiazolecarboxamide...

2000-05-10

2001-08-21

Lambkin, Deborah C. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

Reexamination Certificate

active

06277995

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a process for preparation of a 2-aminothiazolecarboxamide derivative represented by the following formula (I):
wherein R
1
represents straight-chain or branched C
1-5
alkyl, C
1-5
haloalkyl, or C
3-6
cycloalkyl, and R
2
represents C
1-3
alkyl or C
1-3
haloalkyl.
BACKGROUND ART
The compounds of formula (I) are used as microbicides for treating plant diseases caused by Pythiaceae or Peronosporaceae. The compounds of formula (I) were already disclosed in Korean Patent Laid-open Publication No. 94-19960 and the corresponding foreign applications, for example, U.S. Pat. application Ser. No. 08/287,917, JP Patent Application No. 192529 and EP Patent Application No. 94112652.6 which were filed by the present applicant.
Further, a process for preparation of 2-aminothiazolecarboxamide derivatives including the compounds of formula (I) using 2-aminothiazole carboxylic acid as an intermediate was described in Korean Patent Laid-open Publication No. 97-24120. However, this process has the disadvantage that it is not economic when applied to industrial production due to the many steps for obtaining the intermediate and the low yield.
Accordingly, the present inventors have studied to improve the prior process by solving the above mentioned problems, and as a result, have brought the present invention to completion.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for preparation of a 2-aminothiazolecarboxamide derivative represented by the above formula (I) characterized in that an iminothiourea compound represented by the following formula (II):
wherein R
1
and R
2
are defined as previously described, and R
3
represents phenyl which may be optionally mono- to penta-substituted independently by chloro, methoxy, ethoxy, phenoxy or nitro, is reacted with a thiopheneacetamide compound represented by the following formula (III):
wherein Y represents a leaving group such as chloride, bromide, etc.
BEST MODE FOR CARRYING OUT THE INVENTION
The compound of formula (I) can be prepared by reacting the compound of formula (II) with the compound of formula (III) in a solvent and in the presence of a base as depicted in the following Reaction Scheme I:
wherein R
1
, R
2
, R
3
and Y are defined as previously described.
Examples of the base used in the above reaction include an organic base such as triethylamine, tributylamine, diisopropylethylamine, N,N-dimethylaniline, pyridine, 4-dimethylaminopyridine, etc., and an inorganic base such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium hydride, potassium hydride, etc. The organic base is preferred, and the alkyl amine such as triethylamine, tributylamine, diisopropylethylamine, etc. is more preferred. The base can be used in an amount of 1 to 5 equivalents, preferably in an amount of 1 to 2 equivalents.
The above reaction can be carried out at the temperature between 20 and 120° C., preferably between 40 and 80° C., and the reaction time is suitably about 8 to 12 hours.
The solvent includes an alcohol such as methanol, ethanol, isopropyl alcohol, etc.; an aromatic hydrocarbon such as benzene, toluene, xylene, etc.; an ether such as diethylether, dioxane, 1,2-dimethoxyethane, tetrahydrofuiran, etc.; a ketone such as acetone, methylethyl ketone, cyclohexanone, etc.; a nitrile such as acetonitrile, propionitrile, etc.; a halogenated hydrocarbon such as dichloromethane, 1,2-dichloroethane, chloroform, etc.; an ester such as methyl acetate, ethyl acetate, etc.; and a polar solvent such as N,N-diethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., and the alcohol is preferred.
The compound of formula (II) used as a starting material in the Reaction Scheme (I) is novel and can be prepared in accordance with the following Reaction Scheme (II):
wherein R
1
, R
2
and R
3
are defined as previously described.
That is, the compound of formula (II) can be prepared by a process characterized in that
in Step 1, an amide compound represented by the following formula (IV):
wherein R
2
and R
3
are defined as previously described, is reacted with a halogenating agent in a solvent in the presence of a base to produce an imidoylchloride compound represented by the following formula (V):
wherein R
2
and R
3
are defined as previously described;
in Step 2, the resulting imidoylchloride compound of formula (V) is reacted with an isothiocyanide compound represented by the following formula (VII):
MSCN  (VII)
wherein M represents an alkali metal such as sodium, potassium, etc., or NH
4
, by which the chloride group is replaced with the isothiocyanide group to produce an imidoylisothiocyanate compound represented by the following fornula (VI):
wherein R
2
and R
3
are defined as previously described;
in Step 3, the resulting imidoylisothiocyanate compound of formula (VI) is reacted with a primary amine compound represented by the following formula (VIII):
R
1
—NH
2
  (VIII)
wherein R
1
is defined as previously described, in the presence of a base.
In Step 1 for preparing the imidoylchloride compound of formula (V), thionyl chloride(SOCl
2
), phosgene(COCl
2
), phosphorus oxychloride(POCl
3
), etc. can be used as the halogenating agent. The halogenating agent is suitably used in an amount of 1 to 4 equivalents. This reaction is carried out at the temperature between −20° C. and 80° C., preferably between −10° C. and 20° C. The reaction time is suitably about 2 to 5 hours. As the base, an organic base such as pyridine, 4-dimethylaminopyridine, triethylamine, N,N-dimethyl aniline, tributylamine, etc. can be used. A mild base such as pyridine is preferred. The base is suitably used in an amount of 1 to 4 equivalents.
As the solvent, an aromatic hydrocarbon such as benzene, toluene, xylene, etc.; a halogenated hydrocarbon such as dichloromethane, 1,2-dichloroethane, chloroform, etc.; an ether such as diethylether, dioxane, 1,2-dimethoxyethane, tetrahydrofuran, etc.; a ketone such as acetone, methylethyl ketone, cyclohexanone, etc.; a nitrile such as acetonitrile, propionitrile, etc.; an ester such as methyl acetate, ethyl acetate, etc.; or a polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., preferably a halogenated hydrocarbon such as dichloroethane, chloroform, etc. can be used. In addition, N,N-dimethylfonrmamide can be used as a catalyst.
In Step 2, the imidoylisothiocyanate compound of formula (VI) is prepared by reacting the imidoylchloride compound of formula (V) prepared in step 1 with the isothiocyanide compound of formula (VII). The isothiocyanide compound of formula (VII) is suitably used in an amount of 1 to 2 equivalent. The reaction temperature can be between −20° C. and 50° C., preferably between 0° C. and 20° C., and the reaction time ranges suitably from 2 to 5 hours.
In Step 3, the iminothiourea compound of formula (II) is prepared from the imidoylisothiocyanate compound of formula (VI). In this step, the carbon atom of isothiocyanate is attacked by the amine compound of formula (VIII) in the presence of a base, by which the thiourea derivative of formula (II) is produced. The amine compound of formula (VIII) can be used in an amount of 1 to 4 equivalents, preferably 2 to 3 equivalents. This reaction can be carried out at the temperature between −20° C. and 80° C., preferably between 0° C. and 30° C. The reaction time is suitably from 2 to 4 hours.
The above processes according to the present invention will be more specifically explained through the following examples. As typical examples of the compounds of formula (II) according to the present invention, those described in the following table (I) can be mentioned.
TABLE I
COM. NO.
R
1
R
2
R
3
1
ethyl
methyl
phenyl
2
ethyl
ethyl
phenyl
3
ethyl
ethyl
2,6-dichlorophenyl
4
ethyl
ethyl
4-methoxyphenyl
5
ethyl
ethyl
4-phenoxyphenyl
6
ethyl
ethyl
4-nitrophenyl
7
n-butyl
methyl
phenyl
8
n-butyl
ethyl
phenyl
9
isopropyl
ethyl
phenyl
10 
isopropyl
methyl

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