Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1995-01-26
1996-06-18
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
562602, 562603, 562605, C07C 6963
Patent
active
055279546
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP94/ 00588, filed April 07, 1994
FILED OF INDUSTRIAL UTILIZATION
The present invention relates to a process for the production of 2-fluoroisobutyric acid or an ester thereof. The 2-fluoroisobutyric acid or the ester thereof, obtained by the present invention, is useful as an intermediate for a triazine-based herbicide.
PRIOR ART
As a triazine-based herbicide, International PCT Publication W090/09378 discloses a triazine-based herbicide in which a phenoxyalkylamino group is substituted on a triazine ring, for example, as shown by the formula, ##STR1## and this Publication describes that the above triazine-based herbicide has remarkable advantages in that it is not only excellent in herbicidal activity but also free from phytotoxicity to rice on a paddy field.
The phenoxyalkylamino-substituted triazine-based herbicide of this type is obtained by reacting 2-fluoroisobutyrate with 2-phenoxy-1-methyl-ethylbiguanide. As a method for producing 2-fluoroisobutyrate used in the above reaction, U.S. Pat. No. 5,175,345 discloses a method in which 2-hydroxyisobutyrate is reacted (a) with fluorosulfuric acid in the presence or absence of a hydrogen fluoride source or (b) with chlorosulfuric acid in the presence of hydrogen fluoride. This conventional method is shown by a reaction scheme below. ##STR2##
PROBLEMS TO BE SOLVED BY THE INVENTION
In the method using 2-hydroxyisobutyrate as a raw material, described in the above U.S. Patent, 2-fluoroisobutyrate can be obtained at relatively high yields, while a large amount of methacrylate having a boiling point close to that of the 2- fluoroisobutyrate is formed as a byproduct. Industrially disadvantageously, therefore, the post treatment for removing the methacrylate formed as a byproduct is complicated. For achieving high yields, further, a large amount (at least 6 mol per mole of the raw material) of fluorosulfuric acid is required, and it is required to neutralize unreacted fluorosulfuric acid with an alkali such as Ca(OH).sub.2 before disposal. There is hence another defect in that a large amount of waste is formed.
It is therefore an object of the present invention to provide a process which enables the production of 2-fluoroisobutyric acid or its ester in a simple apparatus at high yields while preventing the formation of a byproduct which is difficult to separate.
MEANS TO SOLVE THE PROBLEMS
The present inventors have found that, by reacting 2-hydroxyisobutyric acid or its ester with thionyl chloride and a hydrogen fluoride source, 2-fluoroisobutyric acid or its ester can be produced in a simple apparatus at high yields while preventing the formation of a byproduct, and on basis of this finding, the present invention has been completed.
The object of the present invention therefore consists in a process for the production of 2-fluoroisobutyric acid or its ester, which comprises reacting 2-hydroxyisobutyric acid or its ester with thionyl chloride and a hydrogen fluoride source.
The present invention will be detailed hereinafter.
In the process for the production of 2-fluoroisobutyric acid or its ester, provided by the present invention, the 2-ydroxyisobutyric acid or its ester used as a starting material includes, for example, compounds of the general formula (I), ##STR3## (wherein R is a hydrogen atom or a lower alkyl group).
The compound of the general formula (I) in which R is a hydrogen atom is 2-hydroxyisobutyric acid, and the compound of the general formula (I) in which R is a lower alkyl group is 2-hydroxyisobutyrate. The alkyl group for R includes alkyl groups having to 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl and t-butyl groups.
According to the present invention, the above 2-ydroxyisobutyric acid or its ester is reacted with thionyl chloride and a hydrogen fluoride source, whereby 2-fluoroisobutyric acid or its ester is obtained.
The raw material for the reaction in the present invention is 2-hydroxyisobutyric acid or its ester, while 2-hydroxyisobutyric acid ester
Adachi Ryoichi
Kikukawa Tadashi
Kotsuji Yasuhito
Nishii Masahiro
Geist Gary
Idemitsu Kosan Co. Ltd.
Williams Rosalynd A.
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