Platinum-catalyzed synthesis of dimethylphenol or trimethylphenol from 2,5-dimethylfuran

Abstract

The present invention relates to the production of dimethylphenols, particularly 2,5-dimethylphenol, and trimethylphenols, particularly 2,3,6-trimethylphenol, from 2,5-dimethylfuran, acetylene, and propyne, respectively, in the presence of a platinum catalyst, particularly in MAF gas. The present invention provides a sustainable synthesis of β-tocopherol and α-tocopherol, respectively.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to the synthesis of dimethylphenol or trimethylphenol.

[0002] [Background of the invention] Trimethylphenols and dimethylphenols are important compounds in the synthesis of tocopherols, especially α-tocopherol, especially (all-rac)-α-tocopherol. Several approaches to their synthesis have been proposed.

[0003] WO 2015 / 110654 A1 discloses the synthesis of 2,3,6-trimethylphenol from 2,5-dimethylfuran and propyne using a gold catalyst.

[0004] WO 2015 / 110655 A1 discloses the synthesis of 2,5-dimethylphenol from 2,5-dimethylfuran and acetylene using a gold catalyst.

[0005] The formation of phenolic compounds from 2,5-dimethylfuran and certain substituted alkynes in the presence of a gold(I) catalyst is disclosed in N. Huguet et al., Chem. Eur. J. 2013, 19, 6581-6585. A disadvantage is the formation of hydroarylation by-products, which are regularly formed in large quantities.

[0006] Platinum catalysts are commonly used on a large industrial scale, especially in hydrogenation and oxidation reactions. Therefore, the availability of suitable gold catalysts is significantly limited in volume, making the cost of using gold catalysts significantly higher than that of platinum catalysts. Therefore, using alternative catalysts to gold catalysts has a significant impact on the cost and provides a high financial benefit in the production of tocopherols, 2,5-dimethylphenol and 2,3,6-trimethylphenol, respectively.

[0007] In the methods described in the prior art, expensive catalysts with limited selectivity are applied and the procedures described require separation methods for product isolation.

[0008] The use of 2,5-dimethylfuran is of great interest since it can be obtained from renewable resources (cellulose) as known from the prior art, for example Y. Roman-Leshkov, CJ Barrett, ZY Liu, JA Dumesic, Nature 2007, 447, 982-985.

[0009] The sustainability of chemical processes is of great public and market importance.

[0010] Therefore, there is great interest in the synthesis of 2,5-dimethylphenol and 2,3,6-trimethylphenol from renewable resources.

[0011] [Summary of the Invention] The problem solved by the present invention is therefore to provide a synthetic route to dimethylphenols or trimethylphenols, in particular 2,3,6-trimethylphenol, based on platinum catalysts.

[0012] Surprisingly, it has been found that the method according to claim 1 provides a solution to this problem.

[0013] Surprisingly, it has now been found that the drawbacks of the prior art procedures can be avoided by applying platinum-based catalysts to the reaction of 2,5-dimethylfuran with ethyne or propyne, especially in MAF gas.

[0014] Previously, it was unknown that platinum catalysts could be used to convert 2,5-dimethylfurans and alkynes to dimethylphenols or trimethylphenols with good selectivity, but it has now been discovered that platinum-based catalysts can be used for this synthesis. Surprisingly, the formation of hydroarylation products, as regularly encountered in the respective gold-catalyzed reactions, is not observed.

[0015] Thus, platinum catalysts can be used in this reaction because they are available in large quantities from various suppliers and are known and used for other hydrogenation reactions in the synthesis of α-tocopherol. Naturally, this is even more advantageous from a logistical point of view, since the same catalyst can be used for different steps in the synthesis of vitamin E.

[0016] A further advantage of the present invention is the formation of dimethylphenol or trimethylphenol in high yield and high selectivity in a single step reaction from 2,5-dimethylfuran, and therefore a very sustainable approach to the production of dimethylphenol or trimethylphenol or α-tocopherol, respectively.

[0017] Further aspects of the invention are the subject matter of further independent claims. Particularly preferred embodiments are the subject matter of the dependent claims. [Brief explanation of the drawings]

[0018] [Figure 1] The synthetic route for producing a mixture of 2,4,6-trimethylphenol (=2,4,6-TMP, compound of formula (Ia)) and 2,3,6-trimethylphenol (=2,3,6-TMP, compound of formula (Ib)) from formula (II) is shown schematically. [Figure 2] Dimethylphenol and trimethylphenol are converted to dimethyl or trimethylhydroquinone, respectively, which then react with isophytol (X) or phytol to give α- or β-tocopherol (XI), respectively.

[0019] [Detailed Description of the Invention] In a first aspect, the present invention provides a compound of formula (Ia) and a compound of formula (Ib) [ka] 2. A process for producing a mixture of compounds of formula (II) and (III) in the presence of a Pt catalyst, either in the form of a Pt salt or a Pt complex. [ka] wherein R represents H or CH3, preferably CH3; [ka]

[0020] For the sake of clarity, it is emphasized herein that where the same designation occurs for a symbol or group in several formulas, the definition of said group or symbol given in relation to one particular formula also applies to other formulas containing the same designation.

[0021] 2,5-Dimethylfuran is reacted with either propyne (R=CH3) or acetylene (R=H). Both propyne and acetylene are gases. Their handling is different compared to liquid alkynes. In particular, the dosage and pressure control of each require careful attention and knowledge of each.

[0022] When R represents CH3, propyne can also be mixed with propadiene. Certain mixtures containing propyne and propadiene are known to those skilled in the art as MAF gas (MAF = methylacetylene-arene fraction). MaF gas is an inexpensive process gas and is commercially available from a variety of suppliers.

[0023] The presence of a platinum catalyst is necessary to allow the reaction of 2,5-dimethylfuran with propyne or acetylene to occur. It is important to note that this process uses a platinum catalyst rather than a gold catalyst, making it a platinum-based, gold-free process.

[0024] The platinum catalyst is either in the form of a platinum salt or a platinum complex.

[0025] In one embodiment, the platinum catalyst is preferably a Pt(II) salt, especially PtCl2.

[0026] In another embodiment, the platinum catalyst is preferably a complex of Pt(II), in particular a complex of Pt(II) with at least one organic ligand comprising at least one phosphorus atom, in particular a ligand selected from the group consisting of phosphites, phosphates, phosphonates, and phosphines.

[0027] Particularly preferred as a Pt catalyst is PtCl2 in the presence of an organic ligand containing at least one phosphorus atom, especially a ligand selected from the group consisting of phosphites, phosphates, phosphonates, and phosphines.

[0028] The organic ligand is preferably triphenyl phosphite (P(OPh)), diphenyl phosphate ((PhO)P=O(OH)), triphenyl phosphate ((PhO)P=O), triethyl phosphate ((EtO)P=O), dibenzyl phosphite ((PhCHO)P=O(H)), methyl diphenyl phosphite ((MeO)P(OPh)), triphenylphosphine (P(Ph), P(Ph 5F)3, bis-(2,2,2-trifluoroethyl)-phosphite ((CF3CH2O)2P=O(H)), triethyl 2-fluoro-2-phosphonoacetate ((CHFCOOEt)(EtO)2P=O), tris(2-tolyl)phosphite, ethyl 3-(diethoxyphosphoryl)propanoate (=triethyl 3-phosphonopropionate) ((CH2CH2COOEt)(EtO)2P=O), 2-(diphenylphosphino)benzoic acid (P(Ph)2C6H4COOH), 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (Ultranox 626), P(O-isooctyl)3), P(O-isopropyl)3), P(Oi-PrF6), P(On-Bu), bis(2,4-di-tert-butylphenoxy)-λ2-phosphane, CH3P(EtO)2, 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (= 4-hydroxydinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine 4-oxide), VAPOL hydrogen phosphate (= 18-hydroxy-8,9-diphenyldiphenanthro[4,3-d:3',4'-f][1,3,2]dioxaphosphepine 18-oxide), methyltriphenoxyphosphonium iodide ([CH3P(OPh)3] + I - , 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane ((CH2CH2COOEt)(EtO)2P=O, trimethylolpropane phosphite), trisodium triphenylphosphine trisulfonate (=TPPTS), disodium triphenylphosphine disulfonate (=TPPDS) and sodium triphenylphosphine monosulfonate (=TPPMS); In the formula, Ph represents phenyl, Ph 5F represents pentafluorophenyl, Et represents ethyl, and Me represents methyl.

[0029] The organic ligand is more preferably triphenyl phosphite (P(OPh)), diphenyl phosphate ((PhO)P=O(OH)), dibenzyl phosphite ((PhCHO)P=O(H)), triphenyl phosphate ((PhO)P=O), methyl diphenyl phosphite ((MeO)P(OPh)), trisodium triphenylphosphine trisulfonate (=TPPTS), P(Ph 5F )3, bis-(2,2,2-trifluoroethyl)-phosphite ((CF3CHO)2P=O(H)), tris(2-tolyl)phosphite, ethyl 3-(diethoxyphosphoryl)propanoate (=triethyl 3-phosphonopropionate) ((CH2CH2COOEt)(EtO)2P=O), 2-(diphenylphosphino)benzoic acid (P(Ph)2C6H4COOH), and 9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (Ultranox 626); where Ph represents phenyl and Ph 5F represents pentafluorophenyl, Et represents ethyl, and Me represents methyl.

[0030] The reaction of 2,5-dimethylfuran with propyne or acetylene is preferably carried out in the presence of an ether or ketone, in particular a cyclic ether, preferably tetrahydrofuran, or acetone or methyl ethyl ketone or diethyl ketone (=3-pentanone), preferably acetone or diethyl ketone, more preferably diethyl ketone.

[0031] The amount of the Pt catalyst is more preferably in the range of 0.1 to 25 mol %, particularly preferably 6 to 12 mol %, relative to the compound of formula (II).

[0032] The molar ratio of the organic ligand containing at least one phosphorus atom to Pt is more preferably in the range of 1 to 2, preferably 0.5 to 1.5, and more preferably 0.4 to 1.2.

[0033] The molar ratio of the compound of formula (II) to the compound of formula (III) is preferably in the range of 1:1 to 1:8, particularly in the range of 1:1 to 1:8, and more preferably in the range of 1:1 to 1:3.

[0034] More preferably, the reaction is carried out at a temperature of 0°C to 80°C, particularly 10°C to 60°C, preferably 20°C to 30°C.

[0035] At temperatures above the boiling point of the solvent, the reaction is preferably carried out under pressure.

[0036] The above process produces a mixture of compounds of formula (Ia) and compounds of formula (Ib).

[0037] However, this is of little concern since only compounds of formula (Ib) are reactive in the further reaction sequence to tocopherol.

[0038] As shown schematically in Figure 2, dimethylphenol and trimethylphenol are converted to dimethyl or trimethylhydroquinone, respectively, which then react with isophytol (X) or phytol to form α- or β-tocopherol (XI), respectively.

[0039] However, only dimethylphenols or trimethylphenols of formula (Ib) can form the required hydroquinone of formula (Ib'). Dimethylphenols or trimethylphenols of formula (Ia) have a methyl group para to the phenol group and therefore cannot directly form the required hydroquinone.

[0040] Therefore, the dimethylphenol or trimethylphenol of formula (Ia) does not participate in the further reaction steps of the formation of α-tocopherol, β-tocopherol, respectively, and is removed during the reaction process and / or purification of α-tocopherol or β-tocopherol, respectively.

[0041] When R is H, typically 2,4-DMP (Ia) is predominantly formed, and therefore the molar ratio of 2,4-DMP:2,5-DMP is greater than 50:50.

[0042] As shown above, the formation of a high content in 2,5-DMP is favored due to the presence of a methyl group para to the phenolic OH group in 2,4-DMP.

[0043] The molar ratio of compound of formula (Ia) (=2,4-dimethylphenol = 2,4-DMP) to compound of formula (Ib) (=2,5-dimethylphenol = 2,5-DMP) is typically <70:30, in particular <60:40, preferably <50:50.

[0044] When R is CH3, typically, 2,3,6-TMP (Ib) is mainly formed. Therefore, the molar ratio of 2,4,6-TMP:2,3,6-TMP is typically less than 50:50. Therefore, the molar ratio of the compound of formula (Ia) (=2,4,6-trimethylphenol=2,4,6-TMP):the compound of formula (Ib) (=2,3,6-trimethylphenol=2,3,6-TMP) is preferably ≦50:50, particularly <10:90, more particularly <5:95, preferably <3:97, more preferably <2:98.

[0045] This finding is particularly interesting in the context of the formation of 2,3,6-trimethylphenol and α-tocopherol, respectively, being the most important embodiment of the present invention, primarily due to the fact that the amounts of 2,3,6-trimethylphenol and α-tocopherol, respectively, produced worldwide are several orders of magnitude greater than the amounts of 2,5-dimethylphenol (2,5-DMP) and β-tocopherol, respectively.

[0046] It is therefore highly advantageous to minimize losses due to the formation of unreactive 2,4,6-trimethylphenol or 2,4-dimethylphenol, respectively.

[0047] As a result, it is preferable to use propyne rather than acetylene in the above process. Additionally, it is also advantageous to use MAF as a source of propyne.

[0048] As mentioned above, a mixture of 2,4,6-trimethylphenol (=2,4,6-TMP, compound of formula (Ia)) and 2,3,6-trimethylphenol (=2,3,6-TMP, compound of formula (Ib)) can be prepared from 2,5-dimethylfuran (formula (II)) and propyne or MAF gas (compound of formula (III) with R=methyl), as indicated by step a0) in Figure 1.

[0049] In a further embodiment, a mixture of 2,4,6-trimethylphenol (=2,4,6-TMP, compound of formula (Ia)) and 2,3,6-trimethylphenol (=2,3,6-TMP, compound of formula (Ib)) can be prepared by methylation of a mixture of 2,4-dimethylphenol (=2,4-DMP, compound of formula (Ia-1H)) and 2,5-dimethylphenol (=2,5-DMP, compound of formula (Ib-1H)), as indicated by step a') in Figure 1. The mixture of 2,4-dimethylphenol (=2,4-DMP, compound of formula (Ia-1H)) and 2,5-dimethylphenol (=2,5-DMP, compound of formula (Ib-1H)) can be prepared as described above from 2,5-dimethylfuran (formula (II)) and acetylene (compound of formula (III) with R=H), as indicated by step a0') in Figure 1.

[0050] The methylation in step a') can be carried out by various methods.

[0051] In a preferred manner, a mixture of 2,4-DMP and 2,5-DMP is methylated in the presence of lithium hydroxide monohydrate at elevated temperatures, e.g., with methanol in an autoclave, to give a mixture of mesitol and 2,3,6-TMP, as disclosed in EP 1 108 705 A1, particularly Example 3. The disclosure of the above-mentioned EP patent is incorporated herein in its entirety by reference.

[0052] In an even more preferred manner, the methylation of a mixture of 2,4-DMP and 2,5-DMP is carried out by vapor phase methylation, in particular by exposing the mixture of 2,4-DMP and 2,5-DMP to a mixture of methanol and optionally water in an inert atmosphere in the presence of an oxidation catalyst at a temperature of 300 to 500°C, to give a mixture of mesitol and 2,3,6-TMP.

[0053] This process produces less waste and allows for a continuous process, and is therefore highly advantageous economically and ecologically.

[0054] In a further embodiment, the present invention provides a tocopherol of formula (XI) [ka] A process for producing a) preparing a mixture of a compound of formula (Ia) and a compound of formula (Ib) by a process as discussed in detail above; [ka] b) converting the compound of formula (Ib) into a hydroquinone of formula (Ib') [ka] c) condensation of the hydroquinone of formula (Ib') of step b) with a compound of formula (XA) or (XB) to obtain a tocopherol of formula (XI). [ka] wherein R represents H or CH, preferably CH; and Q is a substituent selected from the group consisting of OH, halide, acyloxy, in particular acetoxy or benzoyloxy, methanesulfonyloxy (=mesyloxy), ethanesulfonyloxy, benzenesulfonyloxy and toluenesulfonyloxy (=tosyloxy); and a wavy line, when connected to a carbon-carbon double bond, represents a carbon-carbon bond that is in either the Z or E configuration).

[0055] When Q represents a halide, preferably Q represents Cl.

[0056] When Q represents acyloxy, the acyloxy is preferably of the formula [ka] (In the formula, R 10 is C 1~6 - represents either an alkyl or aryl group, which may optionally in particular be 1~6 -substituted with an alkyl group).

[0057] Preferably, R 10 is C 1~6 represents either an alkyl or phenyl group.

[0058] More preferably, R 10 represents either a methyl group or a phenyl group, and most preferably represents a methyl group.

[0059] Specific examples of compounds of formula (XA) are isophytol, isophytyl chloride, isophytyl bromide, isophytyl iodide, isophytyl acetate, isophytyl methanesulfonate, isophytyl ethanesulfonate, isophytyl benzenesulfonate and isophytyl toluenesulfonate.

[0060] Specific examples of compounds of formula (XB) are phytol, phytyl chloride, phytyl bromide, phytyl iodide, phytyl acetate, phytyl methanesulfonate, phytyl ethanesulfonate, phytyl benzenesulfonate and phytyl toluenesulfonate.

[0061] The compounds of formula (XB) can be used as E / Z mixtures as well as in the pure E or pure Z form. Their use as E / Z mixtures is preferred.

[0062] Q preferably represents OH or Cl.

[0063] Therefore, the compound of formula (XA) or (XB) is preferably phytol, isophytol, phytyl chloride, or isophytyl chloride, more preferably phytol or isophytol, and most preferably isophytol.

[0064] The use of compounds of formula (XA) is preferred over compounds of formula (XB).

[0065] The details of step a) and its preferred embodiments, amount ratios and conditions have already been described in detail above.

[0066] Steps b) and c) are known to those skilled in the art, for example, primarily from W. Bonrath et al. Angew. Chem. Int. Ed. 2012, 51, 12982-12985 or Bonrath, W. et al. (2021). Vitamins, 4. Vitamin E (Tocopherols, Tocotrienols). In Ullmann's Encyclopedia of Industrial Chemistry. https: / / doi.org / 10.1002 / 14356007.o27_o07.pub2

[0067] In step b), the compound of formula (Ib) is oxidized to the corresponding quinone and subsequently reduced to the hydroquinone of formula (Ib').

[0068] This synthesis process for tocopherol of formula (XI) has the advantage of being highly sustainable. The aromatic moiety is available from the compound of formula (Ib), which was previously discussed in detail. If the side chain building block, i.e., isophytol, is also based on renewable resources, the entire synthesis process for said tocopherol is highly sustainable.

[0069] Since the composition of 2,5-dimethylfuran and acetylene or propyne in the presence of a platinum catalyst results in the production of a mixture of compounds of formula (Ia) and compounds of formula (Ib), in a further aspect the present invention provides a process for the preparation of a mixture of compounds of formula (Ia) and formula (Ib), comprising: with a compound of formula (II); with a compound of formula (III); - a Pt catalyst, either in the form of a Pt salt or a Pt complex; [ka] wherein R represents H or CH3, preferably CH3.

[0070] All components and their preferred embodiments as well as amounts and ratios have already been described in detail above.

[0071] The compound of formula (Ib) is a key intermediate in a novel synthetic route to α-tocopherol and β-tocopherol.

[0072] [Example] The present invention is further illustrated by the following experiments.

[0073] [First Experimental Series (Examples 1 to 26): Reaction of 2,5-dimethylfuran with acetylene] As shown in Table 1, 2,5-dimethylfuran was reacted with acetylene (2 wt %) in an organic solvent and a platinum catalyst.

[0074] For this purpose, under an argon atmosphere, platinum chloride (6 mol%), 2,5-dimethylfuran (1.0 equivalent), and acetylene (1.0 equivalent), dissolved in their respective organic solvents (2% by weight), were added to a 10 ml vial equipped with a magnetic stirrer bar. The vial was then sealed with a cap, and the mixture was stirred in an aluminum block at 23 °C for the time indicated in Table 1. The reaction mixture was then filtered to remove the catalyst and ligand. All volatiles (including unreacted 2,5-dimethylfuran) were removed in vacuo at 50 °C / <30 mbar, yielding an oily residue. The amounts of 2,4- and 2,5-dimethylphenol were determined by GC (gas chromatography). The ratios and yields are shown in Table 1.

[0075] The results in Table 1 show that ligands with aromatic substituents are particularly suitable as part of the platinum catalyst. 5F )3 (tris(pentafluorophenyl)phosphine) is one of the most suitable ligands. Furthermore, Table 1 shows that acetone and 3-pentanone are particularly suitable organic solvents.

[0076] All examples in Table 1 result in mixtures of 2,4-DMP and 2,5-DMP.

[0077] [Table 1]

[0078] [Second Experimental Series (Examples 27-36): Reaction of 2,5-dimethylfuran with propyne] As shown in Table 2, 2,5-dimethylfuran was reacted with propyne (2 wt %) in an organic solvent and a platinum catalyst.

[0079] For this purpose, under an argon atmosphere, platinum chloride (6 mol%), 2,5-dimethylfuran (1.0 equivalent), and propyne (1.0 equivalent), dissolved in their respective organic solvents (2 wt%), were added to a 10 ml vial equipped with a magnetic stirrer bar. The vial was then sealed with a cap, and the mixture was stirred in an aluminum block at 23 °C for the time indicated in Table 2. The reaction mixture was then filtered to remove the catalyst and ligand. All volatiles (including unreacted 2,5-dimethylfuran) were removed in vacuo at 50 °C / <30 mbar, yielding an oily residue. The amounts of 2,4,6-TMP and 2,3,6-TMP were determined by GC (gas chromatography). The ratios and yields are shown in Table 2.

[0080] [Table 2]

[0081] [Third Experimental Series (Examples 37 to 43): Reaction of 2,5-dimethylfuran with MAF] As shown in Table 2, 2,5-dimethylfuran was reacted with MAF gas (2 wt %) in an organic solvent and a platinum catalyst.

[0082] For this purpose, under an argon atmosphere, platinum chloride (6 mol%), 2,5-dimethylfuran (1.0 equivalent), and MAF gas (1.0 equivalent), dissolved in their respective organic solvents (2 wt%), were added to a 10 ml vial equipped with a magnetic stirrer bar. The vial was then sealed with a cap, and the mixture was stirred in an aluminum block at 23 °C for the time indicated in Table 3. The reaction mixture was then filtered to remove the catalyst and ligand. All volatiles (including unreacted 2,5-dimethylfuran) were removed in vacuo at 50 °C / <30 mbar, yielding an oily residue. The amounts of 2,4,6-TMP and 2,3,6-TMP were determined by GC (gas chromatography). The ratios and yields are shown in Table 2.

[0083] [Table 3]

[0084] [Example 44: Methylation: Step a'] A gas-phase flow reactor was charged with an iron oxide-based catalyst (13 g). The reactor was closed and heated under nitrogen until the reactor temperature reached 350°C. The feed consisted of a mixture of 2,5-dimethylphenol and 2,4-dimethylphenol (Example 2) with methanol and water in a molar ratio of 0.35:0.65:30:1.7. The mixture was pumped from top to bottom into the gas-phase reactor at 0.39 ml / min. After the heating zone, the reaction mixture was cooled to room temperature and collected in a bottle. The bottle was emptied and analyzed after 24 hours for 5 days.

[0085] The average conversion and selectivity over the 5 days were: Conversion of 2,5-dimethylphenol: 16% Conversion rate of 2,4-dimethylphenol: 32% Selectivity for 2,3,6-trimethylphenol: 95% The selectivity for 2,4,6-trimethylphenol was 89%.

Claims

1. Compounds of formula (Ia) and compounds of formula (Ib) 【Chemistry 1】 1. A method for preparing a mixture of the formula (II) and the formula (III) in the presence of a Pt catalyst, either in the form of a Pt salt or a Pt complex. 【Chemistry 2】 (Wherein R is H or CH ３ , preferably CH ３ wherein:

2. R is CH ３ 2. The process according to claim 1, characterized in that, when

3. The Pt catalyst is a Pt(II) salt, particularly PtCl ２ 3. The method according to claim 1 or 2, characterized in that:

4. 3. The method according to claim 1 or 2, characterized in that the Pt catalyst is a complex of Pt(II) with at least one organic ligand containing at least one phosphorus atom, in particular a ligand selected from the group consisting of phosphites, phosphates, phosphonates, and phosphines.

5. The Pt catalyst is prepared by the reaction of PtCl 2 in the presence of an organic ligand containing at least one phosphorus atom, in particular a ligand selected from the group consisting of phosphites, phosphates, phosphonates, and phosphines. ２ The method according to any one of claims 1 to 4, characterized in that:

6. The organic ligand is preferably triphenylphosphite (P(OPh) ３ ), diphenyl phosphate ((PhO) ２ P=O(OH)), triphenyl phosphate ((PhO) ３ P=O), triethyl phosphate ((EtO) ３ P=O), dibenzyl phosphite ((PhCH ２ O) ２ P=O(H)), methyl diphenyl phosphite ((MeO)P(OPh) ２ ), triphenylphosphine (P(Ph) ３ ), P(Ph ５Ｆ ) ３ , bis-(2,2,2-trifluoroethyl)-phosphite ((CF ３ CH ２ O) ２ P=O(H)), triethyl 2-fluoro-2-phosphonoacetate ((CHFCOOEt)(EtO) ２ P=O), tris(2-tolyl)phosphite, ethyl 3-(diethoxyphosphoryl)propanoate (=triethyl 3-phosphonopropionate) ((CH ２ CH ２ COOEt) (EtO) ２ P=O), 2-(diphenylphosphino)benzoic acid (P(Ph) ２ C ６ H ４ COOH), 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, P(O-isooctyl) ３ ), P(O-isopropyl) ３ ), P(Oi-PrF ６ ) ３ , P(On-Bu) ３ , bis(2,4-di-tert-butylphenoxy)-λ2-phosphane, CH ３ P(EtO) ２ , 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (= 4-hydroxydinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine 4-oxide), VAPOL hydrogen phosphate (= 18-hydroxy-8,9-diphenyldiphenanthro[4,3-d:3',4'-f][1,3,2]dioxaphosphepine 18-oxide), methyltriphenoxyphosphonium iodide ([CH ３ P(OPh) ３ ] ＋ I － , 4-ethyl-2,6,5-trioxa-1-phosphabicyclo[2.2.2]octane ((CH ２ CH ２ COOEt) (EtO) ２ P=O, trimethylolpropane phosphite), trisodium triphenylphosphine trisulfonate (=TPPTS), disodium triphenylphosphine disulfonate (=TPPDS) and sodium triphenylphosphine monosulfonate (=TPPMS); In the formula, Ph represents phenyl; ５Ｆ 6. The method according to claim 4 or 5, wherein Et stands for ethyl and Me stands for methyl.

7. 7. The process according to any one of claims 1 to 6, characterized in that the reaction is carried out in the presence of an ether or a ketone, in particular a cyclic ether, preferably tetrahydrofuran, or acetone or methyl ethyl ketone or diethyl ketone, preferably acetone or diethyl ketone, more preferably diethyl ketone.

8. 8. The process according to any one of claims 1 to 7, characterized in that the amount of Pt catalyst ranges from 0.1 to 25 mol %, in particular from 6 to 12 mol %, relative to the compound of formula (II).

9. 9. The process according to any one of claims 1 to 8, characterized in that when R is H, the molar ratio of compounds of formula (Ia) to compounds of formula (IIb) is <70:30, in particular <60:40, preferably <50:

50.

10. R is CH ３ 10. The process according to any one of claims 1 to 9, characterized in that when

11. 11. The process according to any one of claims 1 to 10, characterized in that the molar ratio of the compound of formula (II) to the compound of formula (III) is in the range of 1:1 to 1:8, in particular in the range of 1:1 to 1:8, preferably in the range of 1:1 to 1:

3.

12. 12. The process according to any one of claims 1 to 11, characterized in that the reaction is carried out at a temperature of from 0°C to 80°C, in particular from 10°C to 60°C, preferably from 20°C to 30°C.

13. with a compound of formula (II); with a compound of formula (III); - a Pt catalyst, either in the form of a Pt salt or a Pt complex; 【Transformation 3】 (Wherein R is H or CH ３ , preferably CH ３ A composition comprising:

14. Formula (XI) 【Chemistry 4】 A method for producing α-tocopherol of the formula (I), comprising the steps of: a) preparing a mixture of compounds of formula (Ia) and (Ib) by a method according to any one of claims 1 to 12; 【Transformation 5】 b) converting the compound of formula (Ib) into a hydroquinone of formula (Ib'); 【Transformation 6】 c) condensing the hydroquinone of formula (Ib') of step b) with a compound of formula (X-A) or formula (X-B) to obtain a tocopherol of formula (XI); 【Transformation 7】 (Wherein R is H or CH ３ , preferably CH ３ represents; and Q is a substituent selected from the group consisting of OH, halide, acyloxy, in particular acetoxy or benzoyloxy, methanesulfonyloxy (= mesyloxy), ethanesulfonyloxy, benzenesulfonyloxy and toluenesulfonyloxy (= tosyloxy); and the wavy line, when connected to a carbon-carbon double bond, represents a carbon-carbon bond that is in either the Z or E configuration.

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