Method for preparing methyl butyrolactone by hydrogenation of itaconic acid with a metal phosphine complex and triflate salt as a synergistic catalyst

Abstract

The application discloses a method for preparing methyl butyrolactone by hydrogenation of itaconic acid through cooperation of a metal phosphine complex and a trifluoromethanesulfonate, wherein the metal phosphine complex is generated in situ in the reaction by using anhydrous acetic acid metal salt and 1,1,1-tris(diphenylphosphinomethyl)ethane phosphine ligand, the carbon-oxygen double bond is activated by cooperation of the trifluoromethanesulfonate, and the conversion from itaconic acid to methyl butyrolactone is realized under certain temperature and hydrogen pressure. The application uses a cobalt phosphine complex and a trifluoromethanesulfonate cooperation catalytic system, the price of raw materials is relatively low compared with noble metal catalysts, and the efficient conversion from itaconic acid to MGBL can be realized under relatively mild conditions, so that MGBL is obtained in an excellent yield and high selectivity.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and particularly relates to a method for preparing methylbutyrolactone by hydrogenating itaconic acid through the coordinated catalysis of a metal phosphine complex and trifluoromethanesulfonate. Background Art

[0002] Itaconic acid (IA) is an important unsaturated dibasic organic carboxylic acid. Due to its potential value in producing pentameric carbon compounds, such as 2-methyl-1,4-butanediol (2-MBDO) and α- and β-methyl-γ-butyrolactone (MGBL), it is considered a key polybasic carboxylic acid in biomass platform molecules. Therefore, utilizing catalytic conversion technologies to develop itaconic acid downstream products and transform itaconic acid into high-value-added chemicals is of great significance.

[0003] Methyl-gamma-butyrolactone (MGBL) is a renewable chemical with a wide range of applications. Similar to the catalytic hydrogenation of levulinic acid to produce γ-valerolactone, MGBL can also be obtained from the catalytic hydrogenation of itaconic acid. It can be used as a solvent and an important intermediate in the synthesis of other chemicals such as pyrrolidone, as a gasoline additive for valerolactones, and for dyeing cellulose esters and synthetic fibers.

[0004]

[0005] Synthesis of 3-MGBL by a multi-step organic synthesis strategy

[0006] Currently, the synthesis of MGBL (including 2-MGBL and 3-MGBL) is primarily achieved through multi-step organic chemical reactions. Compared to this approach, direct preparation of MGBL via IA-catalyzed hydrogenation offers advantages such as atom economy and has recently been extensively studied. Generally speaking, due to its α,β-unsaturated conjugated structure, itaconic acid is readily hydrogenated to 2-methylsuccinic acid, which is then reduced to MGBL, 2-MBDO (2-methyl-1,4-butanediol), and 3-MeTHF (3-methyltetrahydrofuran).

[0007] In 2010, Jörgen Klankermayer's group published a report on the conversion of IA to 3-MeTHF and 2-MBDO with high selectivity (>90%) using a homogeneous Ru-triphos catalyst in 1,4-dioxane at 195°C under 10 MPa H₂, with or without the addition of p-TsOH and NH₄PF₆. Furthermore, MGBL was obtained with high selectivity (>90%) using Ru-DPPB as a catalyst in THF without any additives (Angew. Chem. Int. Ed. 2010, 49, 5510-5514). In 2011, Avelino Corma's group used TiO₂ as a supported Ru nanoparticle catalyst to obtain MGBL in 90% yield at 150°C under 3.5 MPa H₂ (Chem. Commun., 2011, 47, 3613–3615). In 2019, Eugene Y.-X. Chen's group developed transition metal nanoparticles Ru3(CO 12(TM-NPs) specifically yielded 3-MGBL (70% isolated yield) in the presence of 10 MPa H₂ / CO₂ mixture in the presence of water and 3-MGBL (volume ratio 1:1) (ChemSusChem 2019, 12, 973-977). In 2009, patent CN101781169A reported a two-stage catalytic itaconic acid conversion method that employs esterification followed by hydrogenation rather than direct itaconic acid hydrogenation. Itaconic acid is first esterified with an alcohol to form a dialkyl itaconate. The dialkyl itaconate is then hydrogenated using a Cu-Cr-Mn-Ba / CuO-ZnO catalyst at 150-200°C, 4-8 MPa (H₂ / N₂ pressure ratio 1:3), and methanol as the solvent (methanol:dimethyl itaconate ratio 2:1) to form a mixture of 2-MBDO, 2-MGBL, 3-MGBL, and 2-methylsuccinate in >90% yield. However, the main drawback of this reaction is that it requires esterification of IA, preventing a one-pot production of MGBL, and the yield of MGBL is low (<30%). In 2015, patent CN104923218A reported the use of a catalyst containing metal Ru or Au, preferably supported by one or more of activated carbon, TiO₂, Al₂O₃, ZrO₂, and CeO₂. Using water as the solvent, the metal catalyst was added at a molar ratio of IA to 1.5 mol%, and the reaction was carried out at 180°C under 4 MPa H₂ for 10 h. The maximum yield of MGBL reached 94.8%. In 2016, patent CN201510746345.6 reported a 5% Pd-10% Cu / TiO₂ catalyst. Using 3 mol% of the catalyst in a 1 wt% IA solution in methanol, the reaction was carried out under 4 MPa H₂ at 180°C for 8 h, achieving a yield of MGBL exceeding 90%. In 2019, patent CN109721576A reported a Ru / SiRF catalyst that produced MGBL with a yield of < 40% at an IA aqueous solution concentration of 1-15 wt%, a Ru-based catalyst / IA feed ratio of 2-20 wt%, a reaction temperature of 100-250°C, a hydrogen pressure of 1-10 MPa, and a reaction time of 2-12 h. The disadvantage of this method is that while it uses a noble metal catalyst, its selectivity is very poor. In addition, other catalysts such as Pd / C (Catalysis Communications 61 (2015) 92-96), Pd-yReO x / C (Catalysis Today 274(2016) 88-93), Rh / C, Ir / Al2O 3, Ru / Al2O3 (PCT Patent WO2004005271A1, 2004) and others have also been reported to be used for the hydrogenation conversion of IA.

[0008] Currently, there are several major problems in the conversion of IA to MGBL: 1. The use of precious metal catalysts makes the conversion cost of itaconic acid relatively high; 2. Most of the above catalysts need to be prepared in advance, which makes them difficult to use. Summary of the Invention

[0009] The present invention addresses the problems of the prior art and provides a method for preparing methylbutyrolactone by hydrogenating itaconic acid using a metal phosphine complex and a triflate as catalyst. The method utilizes anhydrous metal acetate and triphos to in situ generate the metal phosphine complex, which then activates the carbon-oxygen double bond with the triflate, achieving highly selective and efficient conversion of IA to MGBL under specific temperature and hydrogen pressure.

[0010] The method of preparing methylbutyrolactone by synergistically catalyzing itaconic acid hydrogenation using a cobalt phosphine complex and a trifluoromethanesulfonate comprises the following steps:

[0011] IA, anhydrous acetate metal salt, 1,1,1-tris(diphenylphosphinomethyl)ethane phosphine ligand (triphos), trifluoromethanesulfonate and solvent were mixed and added to an autoclave reactor. The air in the reactor was replaced with hydrogen and the pressure was maintained at about 1 MPa. The gas was filled and discharged five times, and then the temperature was increased to react. After the reaction was completed, the mixture was diluted with methanol and the MGBL yield was detected by GC.

[0012] The reaction route is as follows:

[0013]

[0014] The anhydrous metal acetate is anhydrous cobalt acetate or anhydrous nickel acetate, preferably anhydrous cobalt acetate.

[0015] The molar ratio of the anhydrous metal acetate to triphos is 1:1.

[0016] The trifluoromethanesulfonates are all commercial reagents, including one or more of Ni(OTf)2, AgOTf, Sc(OTf)3, Fe(OTf)3, Al(OTf)3, and Hf(OTf)4, with Hf(OTf)4 being more preferred.

[0017] The solvent is selected from benzene, ether, and water. Further, the solvent is selected from tetrahydrofuran, trifluorotoluene, dioxane, and water, and is more preferably tetrahydrofuran.

[0018] During the preparation process, the molar ratio of the metal phosphine complex, trifluoromethanesulfonate and itaconic acid is preferably 2.5:5.0:100 to 7.5:7:100, and the most preferred ratio is 7.5:7.5:100.

[0019] During the preparation process, the concentration of itaconic acid in the reaction system is 0.20 mol / L-0.5 mol / L, and the optimal concentration is 0.25 mol / L.

[0020] During the preparation process, the reaction temperature is 160-200° C., preferably 200° C.; the reaction time is 1-12 h, preferably 10 h.

[0021] During the preparation process, the reaction system pressure is 1-6 MPa, preferably 6 MPa.

[0022] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0023] The present invention uses a cobalt phosphine complex and hafnium trifluoromethanesulfonate synergistic catalytic system. The raw material price is cheaper than that of precious metal catalysts. It can achieve efficient conversion of itaconic acid to MGBL under relatively mild conditions, and obtain MGBL with excellent yield and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the product of Example 29 (NMR spectrum of the mixture). After the reaction, the product of Example 29 was concentrated by rotary evaporation, and then 2 drops of sample were taken and treated with deuterated methanol in an NMR tube.

[0025] Figure 2 This is a gas chromatographic analysis chart of the product of Example 28. The retention time 3.598 is dodecane, the retention time 6.467 is 3-methylbutyrolactone, and the retention time 6.627 is 4-methylbutyrolactone. DETAILED DESCRIPTION

[0026] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0027] Example 1: Synthesis of MGBL

[0028] 130.1 mg (1 mmol) of itaconic acid, 13.28 mg (7.5 mol%) of anhydrous cobalt acetate, 46.85 mg (7.5 mol%) of triphos, 38.74 mg (5 mol%) of Hf(OTf)4, and 4 ml of THF were added to a 15 ml autoclave. The autoclave was purged with 1 MPa of H2 five times, and the pressure was then raised to 6 MPa. The temperature was then programmed from an initial temperature of 20°C to 200°C at 3°C / min for 4 h. After the reaction, gas chromatography analysis with dodecane as an internal standard revealed that the conversion of itaconic acid was > 99%, and the total yield of 3-MGBL and 4-MGBL reached 67%.

[0029] Example 2-6:

[0030] The operation process is similar to that of Example 1, except that the trifluoromethanesulfonate is different. The reaction results are shown in Table 1 below.

[0031]

[0032] Examples 7-10:

[0033] The operation process is similar to that of Example 1, except that the concentration of itaconic acid in the reaction system is different. The reaction results are shown in Table 2 below.

[0034]

[0035] Examples 11-15:

[0036] The operation process is similar to that of Example 1, except that the pressure of the reaction system is different. The reaction results are shown in Table 3 below.

[0037]

[0038] Examples 16-19:

[0039] The operation process is similar to that of Example 1, except that the reaction temperature is different. The reaction results are shown in Table 4 below.

[0040]

[0041] Example 20:

[0042] The operation process is similar to that of Example 1, except that anhydrous cobalt acetate is replaced with anhydrous nickel acetate. The reaction results are shown in Table 5 below.

[0043]

[0044] Examples 21-22:

[0045] The operation process was similar to that of Example 1, except that the amount of the complex formed by anhydrous cobalt acetate and 1,1,1-tris(diphenylphosphinomethyl)ethane phosphine ligand was changed. The reaction results are shown in Table 6 below.

[0046]

[0047] Examples 23-25:

[0048] The operation process is similar to that of Example 1, except that the solvent tetrahydrofuran is replaced with other solvents. The reaction results are shown in Table 7 below.

[0049]

[0050] Examples 26-29:

[0051] The operation process is similar to that of Example 1, except that the reaction time is different. The reaction results are shown in Table 8 below.

[0052]

[0053] As can be seen from the above examples, the present invention provides a synergistic catalytic system using inexpensive cobalt phosphine and triflate for the efficient conversion of itaconic acid to MGBL. The advantages of the present invention are: the catalysts are commercially available, inexpensive, do not require prior preparation, are free of precious metals, and are prepared under mild conditions.

Claims

1. A method for preparing methylbutyrolactone by synergistically catalyzing itaconic acid hydrogenation using a metal phosphine complex and a trifluoromethanesulfonate, characterized in that: The metal phosphine complex is generated in situ by using anhydrous metal acetate and 1,1,1-tris(diphenylphosphinomethyl)ethane phosphine ligand in the reaction, which cooperates with trifluoromethanesulfonate to activate the carbon-oxygen double bond, achieving the selective conversion of itaconic acid to methylbutyrolactone at a temperature of 160-200°C and a hydrogen pressure of 1-6 MPa. The anhydrous metal acetate is anhydrous cobalt acetate or anhydrous nickel acetate; The reaction is carried out in a solvent, and the solvent is selected from one of benzene and ether; The reaction scheme is as follows: 。 2. The method according to claim 1, characterized in that The steps include: Itaconic acid, anhydrous metal acetate, 1,1,1-tris(diphenylphosphinomethyl)ethane phosphorus ligand, trifluoromethanesulfonate and solvent are mixed and added into a high-pressure autoclave reactor, the air in the reactor is replaced by hydrogen, and the temperature is raised for reaction to prepare methylbutyrolactone.

3. The method according to claim 1, wherein: The anhydrous metal acetate is anhydrous cobalt acetate.

4. The method according to claim 1, wherein: The molar ratio of the anhydrous metal acetate to the 1,1,1-tris(diphenylphosphinomethyl)ethane phosphorus ligand is 1:

1.

5. The method according to claim 1, wherein: The trifluoromethanesulfonate includes one or more of Ni(OTf)2, AgOTf, Sc(OTf)3, Fe(OTf)3, Al(OTf)3, and Hf(OTf)4.

6. The method according to claim 5, characterized in that: The trifluoromethanesulfonate is Hf(OTf)4.

7. The method according to claim 1, wherein: During the preparation process, the molar ratio of the metal phosphine complex, trifluoromethanesulfonate and itaconic acid is 2.5:5.0:100 to 7.5:7:100.

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