Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1990-02-01
1992-08-04
Lee, Mary C.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
548200, C07D27704, C07D27718
Patent
active
051360420
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for the preparation of thiazolecarboxylic acid chlorides which are useful as starting materials for pharmaceutical products, agricultural chemicals, etc.
BACKGROUND ART
Known conventional processes for the preparation of thiazolecarboxylic acid chlorides include the process using thionyl chloride (Journal of Chemical Society, 1945, 601), (Journal of Heterocyclic Chemistry, 22, 1621 (1985)) and the process employing oxalyl chloride (Journal of Chemical Society Perkin 1, 159, (1982).
In the process making use of thionyl chloride, one or more side reactions occur when the starting thiazolecarboxylic acid is a 2-alkylthiazolecarboxylic acid. It is therefore necessary to maintain the reaction temperature at an extremely low level. A further limitation is imposed on the solvent. The yield is however extremely low even under such reaction conditions.
When a starting material other than 2-alkyl-thiazolecarboxylic acids is employed on the other hand, thionyl chloride undergoes an extremely vigorous reaction with the thiazolecarboxylic acid as the starting material so that the reaction can hardly be controlled. Further, the reaction is accompanied by rapid evolution of heat and immense production of corrosive sulfurous acid gas. As an industrial preparation process, this process therefore involves problems such that extra apparatus and labor are required for the processing of the sulfurous acid gas produced in a large volume.
The process in which oxalyl chloride is used is uneconomical for industrial applications because oxalyl chloride is costly. In addition, this process requires a long reaction time unless a catalyst is employed.
DISCLOSURE OF THE INVENTION
An object of this invention is to obtain a thiazolecarboxylic acid chloride at high purity and yield without need for processing of byproducts while enjoying easy controllability of the reaction.
In order to attain the above object, the present inventors have carried out an extensive investigation with respect to the problems described above. This has resulted in the finding of a preparation process in which a thiazole carboxylic acid is reacted with phosgene or trichloromethyl chloroformate, leading to the completion of the present invention.
Namely, this invention provides a process for the preparation of a thiazolecarboxylic acid chloride represented by the following general formula (II): ##STR3## wherein R.sub.1 represents a hydrogen or halogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkyl group substituted by a halogen atom or lower alkoxy group, and R.sub.2 represents a hydrogen atom, a lower alkyl group, or a lower alkyl group substituted by a halogen atom or lower alkoxy group--hereinafter called the "thiazole-carboxylic acid chloride" --, which comprises reacting a thiazolecarboxylic acid represented by the following general formula (I): ##STR4## wherein R.sub.1 and R.sub.2 have the same meanings as defined with respect to formula (II) --hereinafter called the "thiazolecarboxylic acid" -, with phosgene or trichloromethyl chloroformate in the presence or absence of a catalyst.
According to the process of the present invention, the desired thiazolecarboxylic acid can be obtained at higher purity and yield compared to the conventional techniques.
BEST MODE FOR CARRYING OUT THE INVENTION
As thiazolecarboxylic acids useful as starting materials in the process of the present invention, may be mentioned for example thiazole-5-carboxylic acid, 2-methylthiazole-5-carboxylic acid, 2-ethylthiazole-5-carboxylic acid, 2-iso-propylthiazole-5-carboxylic acid, 2-n-propylthiazole-5-carboxylic acid, 2-n-butyl-thiazole-5-carboxylic acid, 2-iso-butylthiazole-5car acid, 2-sec-butylthiazole-5-carboxylic acid, 2-tert-butylthiazole-5-carboxylic acid, 2-n-pentyl-thiazole-5-carboxylic acid, 2-n-hexylthiazole-5carboxyl acid, 2-fluorothiazole-5-carboxylic acid, 2-chlorothiazole-5-carboxylic acid, 2-bromothiazole-5carboxylic acid, 2-iodothiazole-5-carboxylic acid, 2-methoxythiazole-5-carboxyl
REFERENCES:
patent: 3154578 (1964-10-01), Kinnel et al.
Ishikawa Katsutoshi
Kouno Toshiyuki
Kuwatsuka Toshiaki
Tanaka Yoshinori
Watanabe Seiichi
Lee Mary C.
Mitsui Toatsu Chemicals Inc.
Whittenbough Robert C.
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