Process for preparing polyfluorinated tertiary alcohols

Abstract

The present invention relates to a process for preparing a polyfluorinated alcohol of formula (I) from a ketone of formula (II) and a carboxylic acid salt of formula (III) (R3COO) xY wherein the substituents R1 and R2 are selected from the group consisting of C1-C10 alkyl, C3-C10 cycloalkyl, C6-C14 aryl and C5-C14 heteroaryl wherein the substituents may be unsubstituted or partially or fully fluorinated; r3 is a C1 to C10 alkyl group, which is partially or fully fluorinated; y is a cation selected from the group consisting of K, Li, Na, Cs, Mg, Ca, Fe, Cu, Ag, Zn; x is 1 or 2. In the method, the R3 group of the carboxylate is transferred to the carbonyl carbon of the ketone of formula (II) while releasing CO2. # imgabs0 #

Description

[0001] The present invention relates to a process for preparing a polyfluorinated tertiary alcohol. Furthermore, the present invention relates to the use of the polyfluorinated alcohol prepared by the above process.

[0002] Polyfluorinated alcohols are used as starting materials for the synthesis of compounds used in a variety of consumer products. However, from the prior art, no elegant one-step synthesis method for preparing polyfluorinated tertiary alcohols has been found. In contrast, US 3,317,616 A discloses a stepwise synthesis of polyfluorinated tertiary alcohols from polyfluoroalkyl ketones.

[0003] The general route to prepare polyfluorinated alcohols is based on the addition of Me 3 SiC 3 (Ruppert's reagent). When added to aldehydes, secondary alcohols are formed as described by R. Filler, RM Schure, J. Org. Chem. 1967, 32, 1217-1219. In contrast, when added to ketones, tertiary alcohols are formed as described by GKS Prakash, M. Mandal, Journal of Fluorine Chemistry 2001, 112, 123-131.

[0004] This synthetic strategy consists of using preformed polyfluoroalkyl nucleophiles such as Me 3 SiC 3 (Ruppert's reagent) for trifluoromethylation of ketones or aldehydes, but such reagents have disadvantages due to their high cost.

[0005] Chang et al., Journal of Fluorine Chemistry 2005, 126(6), 937-940 and Tetrahedron Letters 2005, 46, 3161-3164 reported a method that does not require Ruppert's reagent. This is a decarboxylative polyfluoroalkylation reaction in which a polyfluoroalkyl nucleophile is generated in situ from a polyfluorocarboxylate and added to aldehydes and ketones.

[0006] According to this method, benzaldehyde can be converted to the corresponding alcohol in the presence of stoichiometric amounts of Cu(I) halide and trifluoroacetate:

[0007]

[0008] Benzaldehyde (R 2 =H) to prepare the corresponding secondary alcohol, where an extremely high yield of 99% was achieved. However, in the case of the attempted ketone (R 2 =CH 3 ) and esters (R 2 =OCH 3), only trace amounts of the desired product, tertiary alcohol, were detected.

[0009] Gooβen et al. reported in European Journal 2015, 21, 17220–17223 and Journal of Fluorine Chemistry 2017, 198, 89–93 that the presence of an iron catalyst and the use of DMF as a solvent promoted decarboxylative perfluoroalkylation, wherein the above documents only disclosed reactions with aldehydes, which were converted into secondary alcohols. The yield obtained was about 60%:

[0010]

[0011] In view of the above-mentioned disadvantages of the known synthesis methods and the high demand for polyfluorinated tertiary alcohols, it is an object of the present invention to provide a novel, efficient and economical synthesis method for producing polyfluorinated tertiary alcohols.

[0012] Thus, there is provided a process for preparing a polyfluorinated alcohol of formula (I) from a ketone of formula (II) and a carboxylate of formula (III):

[0013]

[0014] in

[0015] R 1 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated;

[0016] R 2 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated;

[0017] R 3 is a partially or fully fluorinated C 1 -C 10 alkyl;

[0018]

[0019] in

[0020] R 1 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated;

[0021] R 2 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated;

[0022] (R 3 COO x Y(III), where

[0023] R 3 is a partially or fully fluorinated C 1 -C 10 alkyl;

[0024] Y is a cation selected from the group consisting of K, Li, Na, Cs, Mg, Ca, Fe, Cu, Ag, Zn;

[0025] x is 1 or 2;

[0026] Features

[0027] The carboxylate R 3 The group is transferred to the carbonyl carbon of the ketone of formula (II), while releasing CO 2 .

[0028] The method of the present invention is very cost-effective and efficient due to its single-step design and the absence of the need to add more expensive reagents. It can achieve large-scale preparation of polyfluorinated tertiary alcohols.

[0029] In the present invention, the term "polyfluorinated alcohol" encompasses alcohols of formula (I) in which the substituents R 1 , R 2 or R 3 At least two hydrogen atoms on at least one carbon atom are substituted with fluorine atoms.

[0030] In the present invention, the term "C1 -C 10 The term "alkyl" encompasses straight-chain or branched saturated hydrocarbon radicals having one to ten carbon atoms. These include in particular methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2,2-dimethylpropyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, isoheptyl, n-octyl, isooctyl, n-nonyl, n-decyl, and the like.

[0031] In the present invention, the term "C 2 -C 10 The term "alkenyl" encompasses unsaturated straight-chain or branched hydrocarbon radicals having two to ten carbon atoms, wherein the hydrocarbon radical has at least one C-C double bond. These include in particular ethenyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, isobutenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, 1-decenyl, and the like.

[0032] In the present invention, the term "C 3 -C 10 "Cycloalkyl" encompasses cyclic saturated hydrocarbon radicals having three to ten carbon atoms. These include in particular cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohexyl, cyclononyl and cyclodecyl.

[0033] In the present invention, the term "C 6 -C 14 "Aryl" encompasses aromatic hydrocarbon radicals having six to fourteen ring carbon atoms. These include in particular phenyl (C 6 H 5 Group), naphthyl (C 10 H 7 Group) and anthracene (C 14 H 9 group).

[0034] In the present invention, the term "C 5 -C 14 "Heteroaryl" encompasses aromatic hydrocarbon radicals having five to fourteen cyclic hydrocarbon atoms, in which at least one hydrocarbon atom is substituted or replaced by a nitrogen, oxygen or sulfur atom. These include in particular pyrrolyl, furyl, thienyl, pyridyl, pyranyl, thiopyranyl and the like. All of the abovementioned hydrocarbon radicals are each bonded to the central atom of the formula (I) via an oxygen atom.

[0035] An advantageous development of the process according to the invention provides that the reaction is carried out in a solvent selected from the group consisting of: DMF, NMP, DMAc, DMSO.

[0036] The above solvent is a solvent suitable for stabilizing the fluorinated carbon anion during the reaction, but the present invention is not limited thereto.

[0037] In the present invention, the term "fluorinated carbanion" encompasses a negatively charged carbon atom whose hydrogen atoms have been replaced by fluorine atoms.

[0038] Abbreviations: DMF, NMP, DMAc, DMSO have the following meanings in the present invention:

[0039] DMF——N,N-dimethylformamide

[0040] NMP——N-methyl-2-pyrrolidone

[0041] DMAc——N,N-dimethylacetamide

[0042] DMSO – Dimethyl sulfoxide

[0043] A further advantageous development of the process according to the invention provides that the reaction is carried out in DMF or DMSO as solvent.

[0044] A most preferred development of the process according to the invention provides that the reaction is carried out in DMF.

[0045] The reaction temperature in the process of the present invention is preferably 100 to 150°C, particularly preferably 130 to 150°C, most preferably 135 to 145°C.

[0046] A most preferred embodiment of the process according to the invention provides for a reaction temperature of 140° C.

[0047] A further advantageous embodiment of the process according to the invention provides that the reaction is carried out with exclusion of water.

[0048] This measure ensures that the very sensitive polyfluorinated ketones as reactants are not converted into the corresponding hydrates in the presence of traces of water during the reaction, which thermally decompose to carboxylic acids and thus have no negative impact on the yield of the desired tertiary polyfluorinated alcohol. 3 The anion is directly converted to HCF due to its very high pKa value 3 and prevents the reaction from proceeding successfully in the presence of strong base.

[0049] A further advantageous development of the process according to the invention provides that the reaction is carried out in the presence of a catalyst.

[0050] This embodiment of the invention proves to be particularly advantageous for less reactive reactants, so that higher yields can be obtained.

[0051] In the context of the present invention, all catalysts known in the prior art and suitable for this purpose, in particular Lewis acids, can be used as catalysts.

[0052] A further advantageous development of the process according to the invention provides that the reaction is carried out in the presence of an iron catalyst.

[0053] In the method of the present invention, the iron catalyst is preferably selected from: FeCl 2 、FeCl 3 , FeBr 3 , FeF 3 , FeTFA 3 、FeSO 4 , Fe 2 (SO 4 ) 3 , particularly preferably selected from FeCl 2 、FeCl 3 Very particularly preferably FeCl 3 As a catalyst.

[0054] When using FeCl 3 When used as a catalyst, BPy (2,2'-bipyridine), TMEDA (N,N,N',N'-tetramethylethylenediamine) or [2.2.2]cryptand can be added to the reaction at a ratio of 1:1 as a ligand.

[0055] The amount of the iron catalyst in the process of the present invention is preferably 10 to 75 mol%, more preferably 15 to 45 mol%.

[0056] A most preferred development of the process according to the invention provides that the amount of iron catalyst is from 20 to 30 mol %.

[0057] Another advantageous development of the process according to the invention provides that the catalyst is selected from the group consisting of: KOtBu, K 2 CO 3 , KCl, ZnCl 2 、CoCl 2 、MnCl 2 、InCl 3 , GaBr 3 、CuI、CuBr、AgBF 3 Sc(OTf) 3 .

[0058] The amount of catalyst in the process of the present invention is preferably 10 to 75 mol%, more preferably 10 to 30 mol%.

[0059] For gaseous reactants, the method of the present invention can be carried out by the following methods, but is not limited to these: crimp container Gas burette and autoclave. In the case of using an autoclave, the reaction pressure is 0.5 to 6.5 bar, preferably 2.0 to 4.0 bar, most preferably 3.0 bar.

[0060] The reaction time is 1 to 24 hours.

[0061] The method of the present invention is suitable for preparing polyfluorinated alcohols of formula (I)

[0062]

[0063] in

[0064] R 1 It is C 1 -C 10 Alkyl groups, which may be unsubstituted or partially or fully fluorinated;

[0065] R 2 It is C 1 -C 10 Alkyl groups, which may be unsubstituted or partially or fully fluorinated;

[0066] R 3 is a partially or fully fluorinated C 1 -C 10 alkyl.

[0067] The method of the present invention is very suitable for preparing polyfluorinated alcohols of formula (I)

[0068]

[0069] in

[0070] R 1 It is C 1 -C 10 Alkyl groups, which may be partially or fully fluorinated;

[0071] R 2 It is C 1 -C 10 Alkyl groups, which may be partially or fully fluorinated;

[0072] R 3 is a partially or fully fluorinated C 1 -C 10 alkyl.

[0073] The process of the invention is particularly suitable for preparing polyfluorinated alcohols of formula (I)

[0074]

[0075] in

[0076] R 1 It is a fully fluorinated C 1 -C 10 alkyl;

[0077] R 2 It is a fully fluorinated C1 -C 10 alkyl;

[0078] R 3 It is a fully fluorinated C 1 -C 10 alkyl.

[0079] The method of the present invention is most suitable for preparing polyfluorinated alcohols of formula (I)

[0080]

[0081] in

[0082] R 1 Selected from CF 3 CF 2 CF 3 CF(CF 3 ) 2 , C(CF 3 ) 3 or CF 2 CF 2 CF 3 ;

[0083] R 2 Selected from CF 3 CF 2 CF 3 CF(CF 3 ) 2 , C(CF 3 ) 3 or CF 2 CF 2 CF 3 ;

[0084] R 3 Selected from CF 3 CF 2 CF 3 CF(CF 3 ) 2 , C(CF 3 ) 3 or CF 2 CF 2 CF 3 .

[0085] The method of the present invention is most suitable for preparing polyfluorinated alcohols:

[0086] I-1a to I-156a, where R 3 For CF 3 , and R 1 and R 2 The corresponding combinations are shown in Table 1;

[0087] I-1b to I-156b, where R 3 For CF 2 CF 3 , and R 1 and R 2 The corresponding combinations are shown in Table 1;

[0088] I-1c to I-156c, where R 3 CF(CF 3 ) 2 , and R 1 and R 2 The corresponding combinations are shown in Table 1;

[0089] I-1d to I-156d, of which R 3 C(CF 3 ) 3 , and R 1 and R 2 The corresponding combinations are shown in Table 1;

[0090] I-1e to I-156e, where R 3 For CF 2 CF 2 CF 3 , and R 1 and R 2 The corresponding combinations are shown in Table 1;

[0091] Table 1

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] The above compounds can be used to prepare electrolytes for battery cells.

[0100] The method of the present invention is described below by way of examples, but is not limited to these examples:

[0101] Example 1 : Preparation of C(CF) from hexafluoroacetone without using catalyst 3 ) 3 OH

[0102]

[0103] The preparation of the above tertiary alcohol can be carried out according to the following method:

[0104] Method 1: Reactions in crimp-top vessels

[0105] A mixture of pre-dried potassium trifluoroacetate (0.36 mmol, 1.00 equiv), 30 μl 1,4-difluorobenzene (as NMR internal standard) (0.29 mmol) and 1 ml dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. The septum cap in this method is perforated. Excess hexafluoroacetone (about 1.1 mmol, about 3.00 equiv) was condensed into the container and stirred at 140 ° C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0106] The yield of the target product was 78%.

[0107] Method 2: Reactions in pressure-resistant crimp vessels

[0108] A mixture of pre-dried potassium trifluoroacetate (0.36 mmol, 1.00 equiv), 30 μl 1,4-difluorobenzene (as NMR internal standard) (0.29 mmol) and 1 ml dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. No Excess hexafluoroacetone (about 1.1 mmol, about 3.00 equivalents) was condensed into the container and stirred at 140°C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0109] The yield of the target product was 73%.

[0110] Method 3: The reaction was carried out in a crimp-top vessel and the substrate was metered in using a gas burette.

[0111] A mixture of pre-dried potassium trifluoroacetate (0.6 mmol, 1.00 equiv), 100 μl 1,4-difluorobenzene (as NMR internal standard) (0.963 mmol) and 1 ml dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. NoThe excess hexafluoroacetone was measured by a gas burette, condensed into a container, and stirred at 140 ° C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0112] The yield of the target product was 76%.

[0113] Method 4: Autoclave

[0114] In a glove box, potassium trifluoroacetate (2.08 mmol, 1.00 equivalent) and 3.5 ml of dimethylformamide were charged into an autoclave (volume about 70 ml) and equipped with a magnetic stirrer. After sealing, excess hexafluoroacetone (measured by a gas measuring tube) was condensed into the autoclave outside the glove box and sealed. The reaction was stirred at 140 ° C for 16 hours. After the reaction was completed, the excess HFA was removed, the autoclave was opened and rinsed. It was then acidified with HCl, and 100 μl of 1,4-difluorobenzene was added as an internal standard, and the reaction was stirred at 140 ° C for 16 hours. 19 The samples were analyzed by FNMR.

[0115] The process was carried out several times at different reaction pressures and the following yields were obtained:

[0116] The yield was 58% at a reaction pressure of 0.7 bar.

[0117] The yield was 57% at a reaction pressure of 1.1 bar.

[0118] The yield was 71% at a reaction pressure of 3.0 bar.

[0119] The yield was 57% at a reaction pressure of 6.5 bar.

[0120] Example 2 : Preparation of C(CF) from hexafluoroacetone in the presence of a catalyst 3 ) 3 OH

[0121]

[0122] The preparation of the above tertiary alcohol can be carried out according to the following method:

[0123] Method 1: Reactions in crimp-top vessels

[0124] A mixture of pre-dried potassium trifluoroacetate (0.36 mmol, 1.00 equiv), iron (III) chloride, 30 μl 1,4-difluorobenzene (as NMR internal standard) (0.29 mmol) and 1 ml dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. The septum cap in this method is perforated. Excess hexafluoroacetone (about 1.1 mmol, about 3.00 equiv) was condensed into the container and stirred at 140 ° C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0125] Using different amounts of FeCl 3 This process was carried out several times and the following yields were obtained:

[0126] FeCl 3 When the amount was 10 mol%, the yield was 95%.

[0127] FeCl 3 When the amount was 20 mol%, the yield was 99%.

[0128] FeCl 3 When the amount was 25 mol%, the yield was 95%.

[0129] FeCl 3 When the amount was 30 mol%, the yield was 96%.

[0130] FeCl 3 When the amount was 40 mol%, the yield was 86%.

[0131] Method 2: Reactions were performed in crimp-top vessels, 0.6 mmol

[0132] A mixture of pre-dried potassium trifluoroacetate (0.6 mmol, 1.00 equiv), iron (III) chloride, 30 μl of 1,4-difluorobenzene (as an NMR internal standard (0.29 mmol) and 1 ml of dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. The septum cap in this method No Excess hexafluoroacetone (about 1.1 mmol, about 3.00 equivalents) was condensed into the container and stirred at 140°C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0133] Using different amounts of FeCl 3 This process was carried out several times and the following yields were obtained:

[0134] FeCl3 When the amount was 10 mol%, the yield was 62%.

[0135] FeCl 3 When the amount was 20 mol%, the yield was 75%.

[0136] FeCl 3 When the amount was 30 mol%, the yield was 67%.

[0137] FeCl 3 When the amount was 40 mol%, the yield was 79%.

[0138] Method 3: Metering of substrate using a gas burette

[0139] A mixture of pre-dried potassium trifluoroacetate (0.6 mmol, 1.00 equiv), catalyst, 100 μl 1,4-difluorobenzene (as NMR internal standard) (0.963 mmol) and 1 ml dimethylformamide (DMF) was placed in a glove box into a 20 ml glass vial with a magnetic stirrer and sealed with a septum cap. The septum cap in this method No The excess hexafluoroacetone was measured by a gas burette, condensed into a container, and stirred at 140 ° C for 16 hours. The reaction mixture was then acidified with HCl and passed through 19 The samples were analyzed by F NMR.

[0140] The process was carried out several times using different catalysts and gave the following yields:

[0141] K 2 CO 3 When the amount was 10 mol%, the yield was 77%.

[0142] The yield was 56% when the amount of KOtBu was 10 mol%.

[0143] Example 3 : Preparation of PhC(CF) from trifluoroacetophenone in the presence of a catalyst 3 ) 2 OH

[0144]

[0145] A mixture of trifluoroacetophenone (0.30 mmol, 1.00 equiv), potassium trifluoroacetate (0.36 mmol, 1.20 equiv), catalyst and 30 μl 1,4-difluorobenzene (as NMR internal standard) (0.29 mmol, 0.963 equiv) was stirred in a glove box in an oven-dried 20 ml glass vial with a magnetic stir bar at 140 °C in 1 ml dimethylformamide for 12 h, then acidified with HCl.

[0146] The process was carried out several times using different catalysts and gave the following yields:

[0147] FeCl 2 When the amount was 30 mol%, the yield was 53%.

[0148] FeBr 3 When the amount was 30 mol%, the yield was 63%.

[0149] GBr 3 When the amount was 30 mol%, the yield was 63%.

[0150] Using different amounts of FeCl 3 This process was carried out several times and the following yields were obtained:

[0151] FeCl 3 When the amount was 15 mol%, the yield was 45%.

[0152] FeCl 3 When the amount was 30 mol%, the yield was 81%.

[0153] FeCl 3 When the amount was 45 mol%, the yield was 85%.

[0154] FeCl 3 When the amount was 60 mol%, the yield was 73%.

[0155] FeCl 3 When the amount was 75 mol%, the yield was 71%.

[0156] By 30 mol% FeCl 3 The method was carried out using different ligands:

[0157] FeCl 3 When the amount was 30 mol% and BPy was the ligand, the yield was 77%.

[0158] FeCl 3 When the amount was 30 mol% and TMEDA was the ligand, the yield was 89%.

[0159] FeCl 3 When the amount was 30 mol% and [2.2.2] cryptand was the ligand, the yield was 42%.

Claims

1. A method for preparing a polyfluorinated alcohol of formula (I) from a ketone of formula (II) and a carboxylate of formula (III) in R 1 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated; R 2 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated; R 3 is a partially or fully fluorinated C 1 -C 10 alkyl; in R 1 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated; R 2 Selected from: C 1 -C 10 Alkyl, C 3 -C 10 Cycloalkyl, C 6 -C 14 Aryl and C 5 -C 14 heteroaryl, wherein the substituents may be unsubstituted or partially or fully fluorinated; (R 3 COO x Y(III), where R 3 is a partially or fully fluorinated C 1 -C 10 alkyl; Y is a cation selected from the group consisting of K, Li, Na, Cs, Mg, Ca, Fe, Cu, Ag, Zn; x is 1 or 2; Features The carboxylate R 3 The group is transferred to the carbonyl carbon of the ketone of formula (II), while releasing CO 2 .

2. The method according to claim 1, It is characterized in that The reaction is carried out in a solvent selected from the group consisting of: DMF, NMP, DMAc, DMSO.

3. The method according to claim 2, It is characterized in that The solvent was DMF.

4. The method according to any one of claims 1 to 3, Features The reaction temperature is 100°C to 150°C.

5. The method according to any one of claims 1 to 4, Features The reaction temperature is 135 to 145°C.

6. The method according to any one of claims 1 to 5, It is characterized in that The reaction is carried out under the condition of excluding moisture.

7. The method according to any one of claims 1 to 6, It is characterized in that The reaction is carried out in the presence of a catalyst.

8. The method according to claim 7, It is characterized in that The catalyst is an iron catalyst.

9. The method according to claim 7 or 8, It is characterized in that The iron catalyst is selected from: FeCl 2 、FeCl 3 , FeBr 3 , FeF 3 , FeTFA 3 、FeSO 4 , Fe 2 (SO 4 ) 3 .

10. The method according to any one of claims 7 to 9, It is characterized in that The amount of the iron catalyst is 10 to 75 mol%, preferably 15 to 45 mol%.

11. The method according to any one of claims 1 to 10, It is characterized in that R 1 C 1 -C 10 Alkyl groups, which may be unsubstituted or partially or fully fluorinated.

12. The method according to any one of claims 1 to 11, It is characterized in that R 3 C 1 -C 10 Alkyl groups, which may be unsubstituted or partially or fully fluorinated.

13. The method according to any one of claims 1 to 12, It is characterized in that R 1 Selected from: CH 3 、CH 2 F、CHF 2 、CF 3 、CH 2 CH 3 、CH 2 CH 2 F、CH 2 CHF 2 、CH 2 CF 3 、CF 2 CF 3 、CF(CF 3 ) 2 、C(CF 3 ) 3 、CF 2 CF 2 CF 3 。 14. The method according to any one of claims 1 to 13, characterized in that R 2 Selected from: CH 3 , CH 2 F. CHF 2 CF 3 , CH 2 CH 3 , CH 2 CH 2 F, CH 2 CHF 2 , CH 2 CF 3 CF 2 CF 3 CF(CF 3 ) 2 , C(CF 3 ) 3 CF 2 CF 2 CF 3 .

15. The method according to any one of claims 1 to 14, It is characterized in that R 3 Selected from: CF 3 , CF 2 CF 3 , CF(CF 3 ) 2 , C(CF 3 ) 3 , CF 2 CF 2 CF 3 .

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