JP2000302723A - Racemization of dihalovinyl-cyclopropanecarboxylic acids - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for racemizing dihalovinyl-cyclopropanecarboxylic acids by which an expensive Lewis acid or a special photoreactional apparatus is not required. SOLUTION: An acid chlorinating agent and titanium tetrachloride are reacted with optically active 2,2-dimethyl-3-(2',2'-dihalovinyl)-cyclopropanecarboxylic acids represented by the general formula (X1 and X2 are each chlorine, bromine or fluorine atom; and Y is chlorine, bromine atom or hydroxy group) to racemize the 2,2-dimethyl-3-(2',2'-dihalovinyl)-cyclopropanecarboxylic acids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for the racemization of 2,2-dimethyl-3- (2 ', 2'-dihalovinyl) -cyclopropanecarboxylic acids.

[0002]

2. Description of the Related Art In the following general formula (1), 2,2-dimethyl-3- (2 ', 2'-dihalovinyl) -cyclopropanecarboxylic acid (hereinafter, referred to as Y) is a hydroxyl group. Dihalic acid) is a compound that constitutes an acid component such as the low-toxic insecticides permethrin and cypermethrin, which exhibit excellent efficacy not only for household and epidemic control but also for agricultural pests and forest pests. It is known that the compound generally has a high (+) insecticidal activity when led to esters which are effective as insecticides. The dihalo acids are usually produced as a racemic form, that is, a (±) form. In the case of an acid, (+) is obtained by an optical resolution method using an organic base, and in the case of an ester, an asymmetric hydrolysis method using an enzyme or the like. Gaining body. Here, a method of using the remaining (-) body after obtaining the (+) body has been required. We have developed a racemization method for various (-) dihalo acids, but a method using a Lewis acid of iodine (JP-A-2-62844)
Japanese Patent Application Laid-Open No. HEI 2-343651) has a problem that the Lewis acid of iodine is expensive and is difficult to obtain industrially. Had the problem of using a photoreaction device that was special and required consideration for disaster prevention.

[0003]

Under the circumstances described above, the present inventors have conducted intensive studies to develop a more improved racemization method, and as a result, have reached the present invention. That is, the present invention provides a compound represented by the general formula (1): (Wherein, X1 and X2 each independently represent a chlorine, bromine or fluorine atom, Y represents a chlorine, bromine atom or a hydroxy group; * represents an asymmetric carbon). -Dimethyl-3- (2 ', 2'-dihalovinyl) -cyclopropanecarboxylic acid, wherein an acid chlorinating agent and titanium tetrachloride are allowed to act on 2,2-dimethyl-3- (2', 2 ' -Dihalovinyl)
The present invention provides a method for racemizing cyclopropanecarboxylic acids (hereinafter, referred to as dihalo acids).

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Examples of the substituents X1 and X2 of the dihalo acids represented by the general formula (1) used in the present invention include a halogen atom such as fluorine, chlorine and bromine, and Y represents a halogen atom such as chlorine and bromine. Or a hydroxy group.

As specific dihalo acids (1), for example, 2,2-dimethyl-3- (2 ′, 2′-dichlorovinyl) -cyclopropanecarboxylic acid, 2,2-dimethyl-3- (2 ', 2'-chlorofluorovinyl) -cyclopropanecarboxylic acid, 2,2-dimethyl-3- (2',
Carboxylic acids such as 2'-difluorovinyl) -cyclopropanecarboxylic acid and 2,2-dimethyl-3- (2 ', 2'-dibromovinyl) -cyclopropanecarboxylic acid, and their acid chlorides and bromides are exemplified. There are a total of four isomers of dihalo acids, (-) cis, (-) trans, (+) cis, and (+) trans, and any of them may be used, Mixtures thereof may be used, but it goes without saying that, for the purpose of the present invention, the use of dihalo acids which are usually rich in the (-) form is significant.

[0006] In the present invention, titanium tetrachloride is used as a catalyst, and its use amount is usually about 0.1 to 2 times the molar amount of the dihalo acids (1). The present invention is carried out in the presence of an acid chlorinating agent. Examples of the acid chlorinating agent include thionyl chloride, sulfuryl chloride, oxalyl chloride, phosgene, diphosgene, triphosgene and the like. The amount of use is usually about 0.5 to 5 times the molar amount of the dihalo acids (1).

The above reaction is usually carried out in the presence of a solvent. Such a solvent is not particularly limited as long as it does not inhibit the reaction. Examples thereof include carbon tetrachloride,
Chloroform, dichloroethane, chlorobenzene, o-
Examples thereof include halogenated hydrocarbons such as dichlorobenzene and m-dichlorobenzene, aromatic hydrocarbons such as benzene, toluene, and nitrobenzene, and nitriles such as acetonitrile and propionitrile, with preference given to halogenated hydrocarbons. The amount of use is usually about 0.5 to 100 times by weight based on the dihalo acid halide (1). The reaction temperature is usually in the range of about 50C to 200C. The reaction time is not particularly limited, but is about several minutes to about 10 hours.

The progress of the reaction is determined by gas chromatography,
It can be confirmed by analytical means such as thin layer chromatography and nuclear magnetic resonance spectrum.

After completion of the reaction, for example, after removing the solvent or the like from the reaction mass, the target compound is converted to Y in the general formula (1) by using a separation means such as distillation or column chromatography.
Is a halogen. After completion of the reaction, the reaction mass can be reacted with water or alkaline water by a conventional method to obtain a dihalo acid in which Y is a hydroxy group in the general formula (1),
By reacting the reaction mass with a lower alcohol, a dihaloester in which Y is a lower alkoxy group in the general formula (1) can also be obtained. By adding 3-phenoxybenzyl alcohol, 5-benzyl-3-furylmethyl alcohol, or the like as an alcohol and reacting directly, a low-toxic insecticide can be induced.

[0010]

According to the method of the present invention, optically active 2,2
2-Dimethyl-3- (2 ', 2'-dihalovinyl) -cyclopropanecarboxylic acid is obtained by using an industrially easily available acid chlorinating agent and titanium tetrachloride, without requiring a special reaction apparatus. It can advantageously be racemized.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 Under a nitrogen atmosphere, levorotatory 2,2-dimethyl-3- (2 ′, 2′-dichlorovinyl) -cyclopropanecarboxylic acid chloride ((+) trans-form 9.0% was placed in a 100 ml flask, (-) Trans form = 91.0%) 1
After adding 0 g and o-dichlorobenzene 100 ml, oxalyl chloride 16.7 g and titanium tetrachloride 8.3 g were added, and the mixture was stirred at 130 ° C. for 1 hour. One hour later, the reaction solution was sampled, converted into (+)-2-octanol ester, and analyzed by gas chromatography. As a result, the optical isomer ratio was (-)-cis isomer: 1
1.4%, (+)-cis form: 15.8%, (-)-trans form: 48.4%, (+)-trans form: 24.4%
Met. Further, excess oxalyl chloride was distilled off under reduced pressure, the temperature was lowered to 50 ° C., and 50 g of water was added. After the addition, the mixture was stirred at 50 ° C. for 30 minutes and allowed to stand, and the organic layer was separated. The obtained organic layer was evaporated, and the obtained crude crystals were recrystallized from hexane to give 6.2 g of 2,2-dimethyl-3- (2 ', 2'-dichlorovinyl) as white crystals. -Cyclopropanecarboxylic acid was obtained.

(Example 2) Under a nitrogen atmosphere, levorotatory 2,2-dimethyl-3- (2 ', 2') was placed in a 100 ml flask.
-Dichlorovinyl) -cyclopropanecarboxylic acid (
(+) Trans-form 9.0%, (-) trans-form = 91.
(0%) and 10 g of o-dichlorobenzene, and then 17.0 g of thionyl chloride and 9.0 g of titanium tetrachloride were added thereto, followed by stirring at 130 ° C. for 1 hour.
One hour later, the reaction solution was sampled, converted into (+)-2-octanol ester, and analyzed by gas chromatography. As a result, the optical isomer ratio was (-)-cis isomer: 8.1%, ( +)-Cis form: 9.5%, (-)-trans form: 47.4%, (+)-trans form: 35.0
%Met. Further, excess thionyl chloride was distilled off under reduced pressure, the temperature was lowered to 50 ° C., and 50 g of water was added. After the addition, the mixture was stirred at 50 ° C. for 30 minutes and allowed to stand, and the organic layer was separated. The obtained organic layer was evaporated, and the obtained crude crystals were recrystallized from hexane to give 6.6 g of 2,2-dimethyl-3- (2 ', 2'-dichlorovinyl) as white crystals. -Cyclopropanecarboxylic acid was obtained.

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Claims (1)

[Claims] 1. The general formula (1) (Wherein, X1 and X2 each independently represent a chlorine, bromine or fluorine atom, Y represents a chlorine, bromine atom or a hydroxy group; * represents an asymmetric carbon). -Dimethyl-3- (2 ', 2'-dihalovinyl) -cyclopropanecarboxylic acid, wherein an acid chlorinating agent and titanium tetrachloride are allowed to act on 2,2-dimethyl-3- (2', 2 ' -Dihalovinyl)
A process for the racemization of cyclopropanecarboxylic acids.