CS219099B1 - Process for the preparation of fluorinated 2-hydryl-tetrahalagenpropanoates - Google Patents

Abstract

The purpose of the invention is to prepare the above substances by a single-step synthesis from fluorinated pentahalopropanoates. The synthesis consists in treating the pentahalopropanoates with ultraviolet radiation in the presence of secondary alcohols and/or cyclic ethers, such as tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and 1,3-dioxane. Aliphatic or alicyclic hydroxyl compounds with a number of carbon atoms of 3 to 6 have proven to be suitable secondary alcohols, such as 2-propanol, 2-butanol, 3-pentanol, 3,3-dimethyl-2-butanol and cyclohexanol, which are used alone or in mixtures. Under these conditions, a selective reduction of the C-Cl or C-Br bond in the vicinity of the carbonyl group occurs.

Description

The invention relates to a process for the preparation of fluorinated 2-hydroxy-tetrahalopropanoates of the general formula

CCl'F _c -CHX-COOR wherein b is 1 and 2, c is 1 to 3, X is chlorine or fluorine, R is alkyl of 1 to 6 or cycloalkyl of 6 to 8 or phenyl or methylphenyl or dimethylphenyl.

Fluorinated carboxylic acids and their functional derivatives are part of the intermediate products of laboratory synthesis and industrial production. Among these substances, tetrahologenepropanoic acid has taken a prominent place, some of which have found use in the field of herbicides. 3-Hydryl-tetrahalopropanoic acids are used for this purpose. In contrast, 2-hydryl-tetrahalopropanoic acids and their functional derivatives have not been readily available by synthesis.

Data on the synthesis of fluorinated 2-hydroxy-tetrahalopropanoic acids are relatively rare in the literature. The starting materials are generally polychlorofluoropropenes. In the case of 2,3,3,3-tetrafluoropropanoic acid, the starting material is hexafluoropropene, which undergoes a stoichiometric loss of organically bound fluorine during a multi-stage synthesis. Thus, the syntheses of fluorinated 2-hydroxy-tetrahalopropanpates are linked to the availability of the starting halopropene.

The disadvantages of the prior art are eliminated by the process for the preparation of 2-hydroxy-tetrahalopropanoates of the general formula

CCl _b F _c -CHX-COOR where h is 1 and 2, c is 1 to 3, X is chlorine or fluorine, R is alkyl of 1 to 6 or cycloalkyl of 6 to 8 or phenyl or methylphenyl or dimethylphenyl, which is based on the pentahalopropanoates of the general formula

CCl _b F _c -CXY-COOR, wherein c, b, X and R are as defined above, Y is chlorine or bromine, is treated with ultraviolet radiation in the presence of secondary alcohols having 3 to 6 carbon atoms and / or tetrahydrofuran and / or tetrahydropyran and / or 1,3-dioxolane and / or 1,4-dioxane and / or 1,3-dioxane. In the starting pentahalopropane, selective halogen reduction occurs from these conditions, whereby bromine is easier to reduce than chlorine and chlorine is significantly easier to reduce than fluorine.

It is sometimes advantageous to use a mixture of isomeric esters, for example a mixture of isopropyl 2,3-dichloro-2,3,3-trifluoropropanoate and isopropyl 2,2-dichloro-3,3,3-trifluoropropanoate for reduction. This gives a mixture of isomeric 2-hydroxy-monochlorotrifluoropropanoates. The ultraviolet radiation effective for reduction is in the region of 200-400 nm and is emitted, for example, by a mercury, xenon, hydrogen or deuterium lamp.

Aliphatic hydroxylates having a carbon number of 3 to 8, such as 2-propanol, 2-butanol, 3-pentanol, 3,3-dimethyl-2-butanol and cyclohexanol, which are used alone or in mixtures, have proved to be secondary alcohols. Among the cyclic ethers, tetrahydrofuran, 1,3-dioxolane, tetrahydropyran, 1,3-dioxane, 1,4-dioxane have been found to be used alone, in mixtures with one another or in mixtures with secondary alcohols.

The above process has a number of advantages, the main one being that the 2-hydroxy-tetrahalopropanoates are obtained in one reaction step. In addition, halogen reduction is a highly selective reaction and proceeds with complete conversion over the time indicated in the examples.

Fluorinated 2-hydroxy-tetrahalopropanoates serve as intermediates, for example, in the synthesis of fluorinated acrylates and as intermediates for the preparation of potential herbicides and pesticides.

The process according to the invention is further described in several exemplary embodiments.

Example 1

A mixture of 68 g of methyl 2,3,3-trichloro-3,3-difluoropropanoate and 250 g of dioxane was irradiated with an ultraviolet detector placed inside the reaction mixture for 120 min. The mixture was then poured onto ice, the organic layer was separated, washed three times with water and dried over anhydrous magnesium sulfate. Rectification under vacuum gave methyl 2,3-dichloro-3,3-difluoropropanoate as the product with a b.p. of 83-85 ° C / 10.7 kPa, a preparative yield of 38.7 g, i.e. 65.2% of theory.

Example 2

A mixture of 77 g of methyl 2-bromo-3-chloro-2,3,3-trifluoropropanoate and 250 g of 1,3-dioxolane was irradiated for 60 minutes with an ultraviolet lamp as in Example 1. The reaction mixture was then poured onto ice, the organic layer was separated, washed three times with water and dried over anhydrous sodium sulfate. The product, methyl 3-chloro-2,3,3-trifluoropropanoate was collected in the rectification range from 77 to 79 ° C / 18 kPa, with a preparative yield of 43.9 g (82%).

Example 3

A mixture of 84 g of cyclohexyl-2,3-dichlorotrifluoropropanoate and 300 g of pinacolinal alcohol (3,3-dimethyl-2-butanol) was irradiated with an ultraviolet lamp for 130 minutes as in Example 1. The reaction mixture was then poured onto ice, the organic layer was separated once washed with calcium chloride solution and three times

213033 washed with water, finally dried over anhydrous magnesium sulfate. The product, i.e. cyclohexyl 3-chloro-2,3,3-trifluoropropanoate, was collected at 94-98 [deg.] C./20 mbar during rectification, yield 42.5 g (58% of theory).

Example 4

A mixture of 76 g of butyl 2,3-dichloro-2,3,3-trifluoropropanoate, 200 g of cyclohexanol and 100 g of 2-butanol was irradiated for 120 minutes with an ultraviolet lamp as in Example 1. The reaction mixture was then poured onto ice, the organic layer was separated, which was washed once with calcium chloride solution and washed three times with water, finally dried over anhydrous sodium sulfate. The product, ie butyl 3-chloro-2,3,3-trifluoropropanoate, was collected in the rectification range 117-120 ° C, yield 46.5 g (71% of theory).

Example 5

A mixture of 59 g of methyl 2-chloro-2,3,3,3-tetrafluoropropanoate, 100 g of tetrahydrofuran and 100 g of 2-propanol was irradiated for 100 minutes as in Example 1. The reaction mixture was then poured onto ice, the organic layer was separated, which was then washed with calcium chloride solution and washed three times with water, finally dried over anhydrous magnesium sulfate. The product, ie methyl 2,3,3,3-tetrafluoropropanoate, was collected in the rectification range from 59 to 61 ° C / 19.1 kPa, the preparative yield was 32.6 g (68% of theory).

Example 6

A mixture of 62 g of isopropyl 2,3-dichloro-2,3,3-trifluoropropanoate, 10 g of isopropyl 2,2-dichloro-3,3,3-trifluoropropanoate and 180 g of 2-propanol was irradiated for 90 minutes as in the example.

1. The reaction mixture was then poured onto ice, the organic layer was separated, which was then washed with calcium chloride solution and washed three times with water, and finally dried over anhydrous sodium sulfate. The product, i.e. a mixture of isopropyl-3-chloro-2,3,3-trifluoropropanoate and isopropyl-2-chloro-3,3,3-trifluoropropanoate, was collected in the rectification range 120-124 ° C, yield 49.8 g (81% of theory).

Example 7

A mixture of 92 g of phenyl 2,3-dichloro-2,3,3-trifluoropropanoate and 220 g of 2-butanol was irradiated for 120 minutes as in Example 1. The reaction mixture was then poured onto ice, the organic layer was separated and then washed calcium chloride solution and three times with water, finally dried over anhydrous magnesium sulfate. The product, ie phenyl-3-chloro-2,3,3-trifluoropropanoate, was collected in the rectification range from 119 to 122 ° C / 3.2 kPa, yield 50.5 g (56% of theory).

Claims (2)

A process for the preparation of fluorinated 2-hydroxy-tetrahalopropanoates of the general formula CCl _b F _c -CHX-COOR where b is 1 and 2, c is 1 to 3, X is chlorine or fluorine, R is alkyl of 1 to 6 or cycloalkyl of 6 to 8 or phenyl or methylphenyl or dimethylphenyl, characterized in that the pentahalopropanoates of the general formula (I) are used CCl _b F _c -CXY-COOR, OF THE INVENTION wherein c is 1 to 3, b is 1 to 3 2, X is chlorine or fluorine, Y is bromine or chlorine, R is alkyl of 1 to 6 or cycloalkyl of 6 to 8, or phenyl or methylphenyl or dimethylphenyl, are exposed to ultraviolet light in the presence of secondary alcohols of number of atoms carbon 3 to 6 and / or tetrahydrofuran and / or tetrahydropyran and / or 1,3-dioxolane and / or 1,4-dioxane and / or 1,3-dioxane.