Catalyst and method for reducing carboxylic ester by ethanol

Abstract

The invention discloses a catalyst and a method for reducing carboxylic ester by ethanol. The catalyst comprises a manganese complex, the manganese complex has the following structure: # imgabs0 #, R1 is selected from C1-C20 alkyl groups or aryl groups, and R2, R3 and R4 are selected from H and C1-C20 alkyl groups or aryl groups. The method comprises the following step: in the atmosphere of hydrogen, nitrogen or inert gas, carrying out reduction reaction on a reaction system containing carboxylic ester, a catalyst, alkali, ethanol serving as a reducing agent and a solvent, so that the carboxylic ester is reduced into the alcohol compound. According to the method for reducing carboxylic ester by catalyzing ethanol through the manganese complex, precious metal is not used as a catalyst, the reaction condition is mild, special hydrogenation reaction equipment is not needed, preparation of various fine chemicals can be achieved, high-valued conversion of waste polyester plastic can be achieved, high-pressure reaction equipment is not needed, operation is easy, and the method is suitable for industrial production. The method has an important application prospect.

Description

Technical Field

[0001] The present invention relates to a method for reducing carboxylic acid esters with ethanol, specifically to a catalyst for reducing carboxylic acid esters with ethanol, and a method for reducing carboxylic acid esters with ethanol catalyzed by a manganese complex, belonging to the technical fields of organic chemistry, catalysis and polymer chemistry. Background Art

[0002] Alcohol compounds are widely used in fields such as medicine, agriculture and materials. The reduction of carboxylic acid esters is an important means for preparing alcohol compounds. Generally, the reduction of carboxylic acid esters requires equivalent metal hydrides, such as lithium aluminum hydride, sodium borohydride, etc. These methods will produce a large amount of waste after use and are not environmentally friendly. In contrast, catalytic hydrogenation of ester groups has the advantages of high atom economy and greenness, meeting the requirements of green development.

[0003] The catalytic hydrogenation of ester groups can be traced back to 1931 at the earliest. Adkins et al. first reported that a heterogeneous Cu-Cr catalyst could reduce carboxylic acid esters to alcohols at 200 °C and a hydrogen pressure of 100 bar. Early ester group catalytic hydrogenation systems generally had problems such as high reaction temperature, high hydrogen pressure, and poor selectivity. In 1980, Grey and Pez et al. first reported that a homogeneous ruthenium hydride catalyst [(Ph3P)2(Ph2P)RuH2 - K + ·diglyme]2 achieved the catalytic hydrogenation of carboxylic acid esters, but the substrates were limited to esters with strong electron-withdrawing groups such as trifluoroacetate and oxalate. In 2006, Milstein et al. used a Ru-PNN pincer complex as a catalyst to achieve the catalytic hydrogenation of aromatic carboxylic acid esters and fatty carboxylic acid esters at a minimum hydrogen pressure of 5.3 bar. Subsequently, a series of catalysts based on noble metals (Ru, Ir, etc.) and non-noble metals (Mn, Fe, Co, etc.) were successfully developed, which could achieve the selective hydrogenation of various aryl carboxylic acid esters or fatty carboxylic acid esters. In contrast, using renewable ethanol as a reducing agent can avoid the use of high-pressure equipment and is more convenient to operate. However, due to the limitations of the catalyst, there are only a few examples of ester group reduction reactions using ethanol as a reducing agent at present. For example, in 2019, the iron-catalyzed reduction of carboxylic acid esters with ethanol was reported in 《Angew.Chem.Int.Ed》, but there was only 1 example of poly(hexylene adipate) for complex polyesters; in 2020, the hydrogenation of monocarboxylic acid esters catalyzed by manganese was reported in 《Chem.Commun.》, with good selectivity. In addition, compared with this, the hydrogenation reduction of polycarboxylic acid esters such as triglyceride and polyethylene terephthalate is still very challenging, and there is currently no suitable catalytic system to achieve its reduction reaction using ethanol as a reducing agent. Therefore, developing a new method for reducing complex esters using ethanol as a reducing agent is of great significance both academically and in industrial production. Summary of the Invention

[0004] The main object of the present invention is to provide a catalyst for the reduction of carboxylic acid esters with ethanol to overcome the deficiencies in the prior art.

[0005] Another object of the present invention is to provide a method for the reduction of carboxylic acid esters with ethanol catalyzed by a manganese complex to improve the efficiency of the prior art.

[0006] To achieve the foregoing invention objects, the technical solutions adopted by the present invention include:

[0007] An embodiment of the present invention provides a catalyst for the reduction of carboxylic acid esters with ethanol, which includes a manganese complex having a structure as shown in formula (I):

[0008]

[0009] Wherein, R 1 is selected from alkyl or aryl groups of C1-C 20 , and R 2 , R 3 and R 4 are selected from H, alkyl or aryl groups of C1-C 20 .

[0010] An embodiment of the present invention also provides a method for the reduction of carboxylic acid esters with ethanol, which includes:

[0011] In an atmosphere of hydrogen, nitrogen or inert gas, a reaction system containing carboxylic acid esters, a catalyst, a base, ethanol as a reducing agent and a solvent is subjected to a reduction reaction, so that the carboxylic acid esters are reduced to alcohol compounds;

[0012] The catalyst includes a manganese complex having a structure as shown in formula (I):

[0013]

[0014] Wherein, R 1 is selected from alkyl or aryl groups of C1-C 20 , and R 2 , R 3 and R 4 are selected from H, alkyl or aryl groups of C1-C 20 .

[0015] Compared with the prior art, the present invention has at least the following advantages:

[0016] 1) The method for the reduction of carboxylic acid esters with ethanol catalyzed by the manganese complex provided by the present invention does not use precious metals as catalysts and has mild reaction conditions;

[0017] 2) The present invention proposes to use ethanol as a reducing agent. The principle is that ethanol dehydrogenates to produce ethyl acetate and hydrogen. The reaction is carried out under atmospheric pressure, which can avoid the use of high-pressure special equipment, making the operation more convenient. Moreover, ethanol has a wide source, is renewable, has no pollutants, and has excellent chemoselectivity. The by-product ethyl acetate is also an important bulk chemical;

[0018] 3) The method for catalytic reduction of carboxylic acid esters with ethanol provided by the present invention can not only achieve the preparation of a variety of fine chemicals, but also realize the high-value conversion of waste polyester plastics. Moreover, it does not require high-pressure reaction equipment, has a simple operation, and has important application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 and Figure 2 are respectively the 1H NMR spectrum and 13C NMR spectrum of ethyl 4-(hydroxymethyl)benzoate in Example 1;

[0021] Figure 3 and Figure 4 are respectively the 1H NMR spectrum and 13C NMR spectrum of p-xylene glycol in Example 1;

[0022] Figure 5 is the 1H NMR spectrum of oleyl alcohol;

[0023] Figure 6 , Figure 7 , Figure 8 and Figure 9 are respectively the gas chromatograms of corn oil, soybean oil, sweet almond oil, and blended oil after the reaction. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In view of the defects of the prior art, the inventors of this case have, through long-term research and a large number of practices, been able to propose the technical solution of the present invention, which mainly uses a manganese complex with a quinoline skeleton as a catalyst and ethanol as a reducing agent to selectively reduce the ester groups of alkyl carboxylic acid esters, aryl carboxylic acid esters, oils and fats, and polyesters. The following will further explain the technical solution, its implementation process, principle, etc.

[0025] Specifically, as an aspect of the technical solution of the present invention, a catalyst for reducing carboxylic acid esters with ethanol involves a manganese complex, and the manganese complex has a structure as shown in formula (I):

[0026]

[0027] Among them, R 1 is selected from C1-C 20 alkyl or aryl, and R 2 , R 3 and R 4 are each independently selected from any one or a combination of more than one of H, C1-C 20 alkyl or aryl, etc.

[0028] As another aspect of the technical solution of the present invention, the preparation method of the manganese complex involved includes:

[0029] First, prepare a tridentate pincer ligand having the structure shown in formula (1);

[0030]

[0031] React the tridentate pincer ligand with a metal manganese catalyst precursor to obtain the manganese complex shown in formula (I).

[0032]

[0033] Among them, R 1 is selected from C1-C 20 alkyl or aryl, and R 2 , R 3 and R 4 are each independently selected from any one or a combination of more than one of H or C1-C 20 alkyl or aryl, etc.

[0034] In some preferred embodiments, the metal manganese catalyst precursor includes Mn(CO)5Br.

[0035] In some preferred embodiments, the preparation method of the tridentate pincer ligand having the structure shown in formula (1) mainly includes: in a protective atmosphere, using 8-fluoroquinaldine as the starting material, and efficiently synthesizing a series of tridentate pincer ligands with a novel PNN-type quinaldine skeleton through 4-6 steps.

[0036] The ligand structure provided by the present invention is the first PNN-type tridentate pincer skeleton based on the quinoline skeleton and the corresponding manganese catalyst. By connecting the Csp 2 site through the P atom and the Csp 3 site through the N atom in the quinoline skeleton, a unique spatial and electronic effect distribution is formed, significantly improving the selectivity of the metal catalyst.

[0037] In some embodiments, a preparation method of a novel tridentate pincer ligand includes:

[0038] In a protective atmosphere, 8-fluoroquinaldine and selenium dioxide are reacted to obtain a substituted 8-fluoroquinoline-2-carbaldehyde having the structure shown in formula (2);

[0039] The substituted 8-fluoroquinoline-2-carbaldehyde is mixed with a primary amine R 3 NH2, a reducing agent is added, the reaction is then quenched, and Boc2O is added for reaction to obtain a product shown in formula (3);

[0040] A phosphine lithium reagent R 1 R 1 PLi is reacted with the product shown in formula (3) to obtain a product shown in formula (4); then, acid treatment is carried out to prepare a tridentate pincer ligand shown in formula (5).

[0041]

[0042] R 1 is selected from an alkyl or aryl group of C1-C 20 and R 3 is selected from any one or a combination of more than one of H or an alkyl or aryl group of C1-C 20

[0043] In some other embodiments, a method for preparing a tridentate pincer ligand includes:

[0044] In a protective atmosphere, 8-fluoroquinaldine and selenium dioxide are reacted to obtain a substituted 8-fluoroquinoline-2-carbaldehyde having the structure shown in formula (2);

[0045] The substituted 8-fluoroquinoline-2-carbaldehyde is reacted with a Grignard reagent R 2 MgBr to obtain an alcohol shown in formula (6), and then reacted with a first base to obtain a chlorine-containing compound shown in formula (7);

[0046] The chlorine-containing compound shown in formula (7) is reacted with an amination reagent R 3 R 4 NH, a second base, and an iodine-containing additive to obtain a product shown in formula (8);

[0047] A phosphine lithium reagent R 1 R 1 pLi is reacted with the product shown in formula (8) to prepare a tridentate pincer ligand shown in formula (1);

[0048]

[0049]

[0050] Among them, R 1 is selected from C1-C 20 ​An alkyl or aryl group, R 2 、R 3 and R 4 are each independently selected from any one or more combinations of H or an alkyl or aryl group having 1 to C 20 .

[0051] In some preferred embodiments, in the above preparation method, the preparation method of the substituted 8-fluoroquinoline-2-carbaldehyde specifically comprises: in a protective atmosphere, heating a mixed reaction system comprising 8-fluoroquinaldine, selenium dioxide and a first solvent to 50-150 °C and reacting for 1-24 h to obtain the substituted 8-fluoroquinoline-2-carbaldehyde.

[0052] In some preferred embodiments, the molar ratio of the 8-fluoroquinaldine to selenium dioxide is 1:0.5 to 1:10.

[0053] Further, the first solvent may include any one or a combination of two or more of N,N-dimethylformamide, dichloromethane, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, acetone, tetrahydrofuran, and toluene, but is not limited thereto.

[0054] In some preferred embodiments, the preparation method specifically comprises: mixing the substituted 8-fluoroquinoline-2-carbaldehyde with a second solvent, adding a primary amine R 3 NH2 and stirring at room temperature for 12-24 h, concentrating the solvent, adding a third solvent and a reducing agent, continuing to stir, quenching the reaction, and then adding Boc2O and reacting at 0-150 °C for 1-24 h to obtain the product shown in formula (3).

[0055] In some preferred embodiments, the molar ratio of the substituted 8-fluoroquinoline-2-carbaldehyde, the primary amine to the reducing agent is 1:1:1 to 1:5:10.

[0056] Further, the reducing agent may include any one or a combination of two or more of sodium borohydride, sodium cyanoborohydride, sodium acetylborohydride, lithium borohydride, lithium aluminum hydride, borane, and red aluminum, but is not limited thereto.

[0057] Further, the second solvent may include any one or a combination of two or more of diethyl ether, dichloromethane, N,N-dimethylformamide, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, tetrahydrofuran, and toluene, but is not limited thereto.

[0058] Further, the third solvent may include any one or a combination of two or more of methanol, ethanol, isopropanol, 1,4-dioxane, and tetrahydrofuran, but is not limited thereto.

[0059] In some preferred embodiments, the preparation method specifically includes: reacting a lithium phosphine reagent R 1 R 1 PLi with the product shown in formula (3) in a fourth solvent at -78 to 150 °C for 6 to 48 h to obtain the product shown in formula (4).

[0060] In some preferred embodiments, the molar ratio of the product shown in formula (3) to the lithium phosphine reagent R 1 R 1 PLi is 1:0.5 to 1:10.

[0061] Furthermore, the fourth solvent may include any one or a combination of two or more of diethyl ether, 1,4-dioxane, tetrahydrofuran, etc., but is not limited thereto.

[0062] In some preferred embodiments, the preparation method specifically includes: subjecting the product shown in formula (4) to acid treatment with an N-deprotecting reagent to obtain the tridentate pincer ligand shown in formula (5).

[0063] In some preferred embodiments, the molar ratio of the product shown in formula (4), the tridentate pincer ligand shown in formula (5) to the N-deprotecting reagent is 1:1:1 to 1:5:10.

[0064] In some preferred embodiments, the preparation method specifically includes: mixing the substituted 8-fluoroquinoline-2-carbaldehyde with a fifth solvent and adding a Grignard reagent R 2 MgBr at -78 to 50 °C for reaction to obtain the alcohol shown in formula (6).

[0065] In some preferred embodiments, the molar ratio of the substituted 8-fluoroquinoline-2-carbaldehyde to the Grignard reagent is 1:0.5 to 1:10.

[0066] Furthermore, the fifth solvent may include any one or a combination of two or more of diethyl ether, 1,4-dioxane, tetrahydrofuran, etc., but is not limited thereto.

[0067] In some preferred embodiments, the preparation method specifically includes: reacting the alcohol shown in formula (6), thionyl chloride with a first base to obtain the chlorine-containing compound shown in formula (7), wherein the reaction temperature is 25 to 150 °C and the reaction time is 1 to 24 h.

[0068] In some preferred embodiments, the molar ratio of the alcohol shown in formula (6), thionyl chloride to the first base is 1:1:0.01 to 1:10:5.

[0069] Further, the first base may include any one or a combination of two or more of triethylamine, triethylenediamine (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4-dimethylaminopyridine (DMAP), pyridine, potassium tert-butoxide, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, etc., but is not limited thereto.

[0070] In some preferred embodiments, the preparation method specifically includes: reacting the chlorine-containing compound represented by formula (7), the amination reagent R 3 R 4 NH, the second base, and the iodine-containing additive at 0 to 150 °C for 12 to 24 h to obtain the product represented by formula (8).

[0071] In some preferred embodiments, the molar ratio of the chlorine-containing compound represented by formula (7), the amination reagent R 3 R 4 NH, the second base to the iodine-containing additive is 1:1:1:0.01 to 1:5:10:5.

[0072] Further, the second base may include any one or a combination of two or more of sodium hydroxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium hydride, potassium hydride, and potassium phosphate, etc., but is not limited thereto.

[0073] In some preferred embodiments, the preparation method specifically includes: reacting the lithium phosphine reagent R 1 R 1 PLi with the product represented by formula (8) in a fourth solvent at -78 to 150 °C for 6 to 48 h to prepare the tridentate pincer ligand represented by formula (1).

[0074] In some preferred embodiments, the molar ratio of the product represented by formula (8) to the lithium phosphine reagent is 1:0.5 to 1:10.

[0075] In some more specific embodiments, the preparation method of the tridentate pincer ligand having the structure represented by formula (5) includes:

[0076] In a protective atmosphere, heating a mixed reaction system containing 8-fluoroquinaldine, selenium dioxide, and a first solvent to 50 to 150 °C and reacting for 1 to 24 h to obtain substituted 8-fluoroquinoline-2-carbaldehyde;

[0077] Mixing the substituted 8-fluoroquinoline-2-carbaldehyde with a second solvent, adding a primary amine R 3NH2 was stirred at room temperature for 12 - 24 h. After concentrating the solvent, a third solvent and a reducing agent were added, and stirring was continued followed by quenching the reaction. After post-treatment, a crude secondary amine product was obtained. Boc2O was added and the reaction was carried out at 0 - 150 °C for 1 - 24 h to obtain the product shown in formula (3). Using the in-situ prepared lithium phosphine reagent R 1 R 1 PLi and the product shown in formula (3) were reacted in a fourth solvent at -78 - 150 °C for 6 - 48 h to obtain the product shown in formula (4). After acid treatment, deprotection was carried out to obtain the novel tridentate pincer ligand shown in formula (5).

[0078]

[0079] Wherein, R 1 is selected from alkyl or aryl groups of C1 - C 20 , and R 3 is selected from any one or a combination of more than one of H or alkyl or aryl groups of C1 - C 20 .

[0080] In some more specific embodiments, the preparation method of the tridentate pincer ligand having the structure shown in formula (1) includes:

[0081] In a protective atmosphere, a mixed reaction system containing 8-fluoroquinaldine, selenium dioxide and a first solvent was heated to 50 - 150 °C and reacted for 1 - 24 h to obtain substituted 8-fluoroquinoline-2-carbaldehyde;

[0082] The obtained 8-fluoroquinoline-2-carbaldehyde was mixed with a fifth solvent and Grignard reagent R 2 MgBr was added at -78 - 50 °C to obtain the corresponding alcohol shown in formula (6); subsequently, the alcohol was reacted with thionyl chloride and a first base to obtain the chlorine-containing compound shown in formula (7). The chlorine-containing compound was reacted with an amination reagent R 3 R 4 NH, a second base, and an iodine-containing additive at 0 - 150 °C for 12 - 24 h to obtain the product shown in formula (8). Using the in-situ prepared lithium phosphine reagent R 1 R 1 PLi and the product shown in formula (8) were reacted in a fourth solvent at -78 - 150 °C for 6 - 48 h to obtain the novel tridentate pincer ligand shown in formula (1).

[0083]

[0084] Wherein, R 1 is selected from alkyl or aryl groups of C1 - C 20 , and R 2 , R 3 and R 4 are selected from H or C1 - C 20A combination of any one or more of an alkyl group or an aryl group.

[0085] Specifically, the synthesis method of the tridentate pincer ligand with the structure shown in formula (1) or formula (5) includes the following steps:

[0086]

[0087]

[0088] Furthermore, R 1 is selected from phenyl, R 2 and R 4 are hydrogen, and when R 3 is benzyl, the structural formula of the ligand is:

[0089]

[0090] And its NMR and high-resolution characterization data are: 1 H NMR(400MHz, CDCl3)δ8.08(d, J = 8.4Hz, 1H), 7.78(d, J = 8.4Hz, 1H), 7.40 - 7.19(m, 17H), 7.10 - 7.07(m, 1H), 3.92(s, 2H), 3.56(s, 2H), 2.45(br, 1H); 13 C NMR(151MHz, CDCl3)δ159.1, 148.7(d, J = 15.9Hz), 140.3, 138.6(d, J = 12.1Hz), 137.7(d, J = 10.0Hz), 136.6, 134.4(d, J = 20.7Hz), 133.9, 128.7, 128.6(d, J = 7.2Hz), 128.4(d, J = 5.1Hz), 126.9(d, J = 2.4Hz), 126.2, 121.1, 54.1, 53.0; 31 P NMR(243MHz, CDCl3)δ - 13.2; HRMS(ESI)calcd.for C 29 H 26 N2P[M + H]: 433.1834, found: 433.1819.

[0091] Furthermore, R 1 is selected from phenyl, R 2 and R 4 are hydrogen, and when R 3 is cyclohexyl, the structural formula of the ligand is:

[0092]

[0093] And its nuclear magnetic resonance and high-resolution characterization data are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.41 - 7.29 (m, 12H), 7.09 - 7.06 (m, 1H), 4.08 (s, 2H), 2.44 - 2.39 (m, 1H), 1.76 - 1.53 (m, 5H), 1.15 - 0.96 (m, 5H); 13 C NMR (151 MHz, CDCl3) 6 148.5 (d, J = 15.9 Hz), 138.2 (d, J = 12.4 Hz), 137.5 (d, J = 10.6 Hz), 137.1, 134.4 (d, J = 20.4 Hz), 128.8, 128.6 (d, J = 7.4 Hz), 128.5, 127.0, 126.5, 120.8, 57.0, 51.4, 32.6, 25.9, 25.0; 31 P NMR (162 MHz, CDCl3) δ -13.7; HRMS (ESI) calcd. for C 28 H 30 N2P [M + H]: 425.2147, found: 425.2139.

[0094] Furthermore, R 1 is selected from phenyl, R 2 is methyl, R 3 is cyclohexyl, R 4 is hydrogen, and the structural formula of the ligand is:

[0095]

[0096] And its nuclear magnetic resonance characterization data are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.09 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.0 Hz, 1H), 7.38 7.30 (m, 12H), 7.08 7.05 (m, 1H), 4.02 (q, J = 6.8 Hz, 1H), 2.11 - 2.05 (m, 1H), 1.80 - 1.76 (m, 1H), 1.62 - 1.42 (m, 4H), 1.16 (d, J = 6.4 Hz, 3H), 1.04 - 0.86 (m, 5H); 13CNMR (151 MHz, CDCl3) δ 148.6, 148.4, 138.6, 138.5, 138.0, 137.8, 137.7, 136.4, 134.4, 134.3, 134.2, 134.1, 133.7, 128.4, 128.4, 128.3, 128.2, 126.7, 125.9, 120.1, 55.7, 54.4, 33.9, 33.0, 26.1, 25.2, 25.0, 23.4; 31 P NMR (162 MHz, CDCl3) δ -13.2; HRMS (ESI) calcd. for C 28 H 30 N2P [M+H]: 439.2303, found: 439.2284.

[0097] In some more preferred specific embodiments, the specific reaction steps of the tridentate pincer ligand having the structure shown in formula (5) are as follows:

[0098] Under nitrogen protection, 8-fluoroquinaldine, selenium dioxide and a first solvent are added to a reaction flask, heated to 50 - 150 °C and reacted for 1 - 24 hours, cooled and filtered, and the substituted 8-fluoroquinoline-2-carbaldehyde shown in formula (2) is obtained by column chromatography separation. Subsequently, the substituted 8-fluoroquinoline-2-carbaldehyde, primary amine R 3 NH2 and a second solvent are added to a reaction flask, stirred at room temperature for 12 - 24 hours, the solvent is concentrated, a third solvent and a reducing agent are added, and the reaction is continued and then quenched. After post-treatment, a secondary amine crude product is obtained, Bo c2 O is added and reacted at 0 - 150 °C for 1 - 24 h to obtain the product shown in formula III. Using the in-situ prepared lithium phosphine reagent R 1 R 1 pLi reacts with the product shown in formula (3) in a fourth solvent at -78 - 150 °C for 6 - 48 h to obtain the product shown in formula (4). After treatment with trifluoromethanesulfonic acid, deprotection is carried out to obtain the novel tridentate pincer ligand shown in formula (5).

[0099] In some more preferred specific embodiments, the specific reaction steps of the tridentate pincer ligand having the structure shown in formula (1) are as follows:

[0100] Under nitrogen protection, 8-fluoroquinaldine, selenium dioxide and a first solvent are added to a reaction flask, heated to 50 - 150 °C and reacted for 1 - 24 hours, cooled and filtered, and the substituted 8-fluoroquinoline-2-carbaldehyde shown in formula (2) is obtained by column chromatography separation. Under nitrogen protection, the substituted 8-fluoroquinoline-2-carbaldehyde is mixed with a fifth solvent and added to the Grignard reagent R 2MgBr to obtain the corresponding alcohol shown in formula (6); subsequently, the alcohol is reacted with thionyl chloride and a first base to obtain a chlorine-containing compound shown in formula (7). The chlorine-containing compound reacts with an amination reagent R 3 R 4 NH, a second base, and an iodine-containing additive at 0 - 150 °C for 12 - 24 h to obtain a product shown in formula (8). Using an in-situ prepared lithium phosphine reagent R 1 R 1 PLi reacts with the product shown in formula (8) in a fourth solvent at -78 - 150 °C for 6 - 48 h to obtain a novel tridentate pincer ligand shown in formula (1).

[0101] In some preferred embodiments, the preparation method specifically includes: mixing the tridentate pincer ligand and a metal manganese catalyst precursor in a sixth solvent and heating for reaction to obtain a novel tridentate pincer manganese complex. Specifically, the reaction process is as follows:

[0102]

[0103] In some preferred embodiments, the molar ratio of the tridentate pincer ligand to the metal manganese catalyst precursor is 1:2 - 10:1, preferably 1:1 - 3:1.

[0104] Furthermore, the sixth solvent may include any one or a combination of two or more of tetrahydrofuran, toluene, benzene, dichloromethane, methanol, ethanol, isopropanol, ether, n-hexane, and 1,4-dioxane, etc., but is not limited thereto.

[0105] In some preferred embodiments, the reaction temperature is 25 - 150 °C, preferably 50 - 110 °C, and the reaction time is 6 - 36 h.

[0106] In some more preferred specific embodiments, the specific reaction steps included in the preparation method are as follows: under a nitrogen atmosphere, add a tridentate pincer ligand, a metal manganese catalyst precursor, and a sixth solvent with the structural formula shown in (1) to a reaction flask, and heat for reaction for 6 - 36 hours. After returning to room temperature, obtain the target tridentate pincer manganese complex with the structure shown in formula (I) through steps such as concentration, washing, centrifugation, and concentration.

[0107] As a preferred technical solution, the preparation method includes: adding a tridentate pincer ligand, a metal manganese catalyst precursor Mn(CO)5Br, and a sixth solvent to a reaction flask, and heating to 25 - 150 °C for reaction for 6 - 36 hours. After the reaction is completed, cool to room temperature, drain the solvent, transfer the reaction flask into a glove box, add a solvent for washing, centrifugation, and concentration to obtain an orange-red solid, which is a tridentate pincer manganese complex with the structure shown in (I).

[0108] In summary, the tridentate pincer manganese complex prepared by the present invention has a novel framework structure and has shown excellent catalytic activity in the reaction of hydrogenating polyesters to prepare diol compounds and other reactions through preliminary tests. The preparation method has mild conditions, simple operation, and is easy to industrialize. The obtained pincer manganese catalyst will have broad application prospects in the future.

[0109] Another aspect of the embodiment of the present invention provides a method for reducing carboxylic acid esters with ethanol, which includes:

[0110] In an atmosphere of hydrogen, nitrogen or inert gas, a reaction system containing a carboxylic acid ester, a catalyst, a base, ethanol as a reducing agent and a solvent is subjected to a reduction reaction, so as to reduce the carboxylic acid ester to an alcohol compound;

[0111] The catalyst includes a manganese complex, and the manganese complex has a structure as shown in formula (I):

[0112]

[0113] wherein, R 1 is selected from an alkyl group or an aryl group of C1-C 20 , and R 2 , R 3 and R 4 are each independently selected from H, an alkyl group or an aryl group of C1-C 20 .

[0114] In some more preferred specific embodiments, a method for reducing carboxylic acid esters with ethanol using a manganese complex specifically includes: in an atmosphere of hydrogen, nitrogen or inert gas, a reaction system containing a carboxylic acid ester, a catalyst, a base and ethanol and a solvent is reacted at a temperature above 50 °C, so as to reduce the carboxylic acid ester to an alcohol compound.

[0115] Further, the inert gas includes argon, but is not limited thereto.

[0116] In some preferred embodiments, the structure of the carboxylic acid ester is as shown in formula (II), formula (III) or formula (IV):

[0117]

[0118] wherein, R and R' are each independently selected from a fatty group containing C1-C 40 or an aryl group containing C6-C 60 , and n is 1-500.

[0119] Further, the carboxylic acid ester as described in formula (IV) may also be a beverage bottle, outer packaging or used clothing containing polyethylene terephthalate.

[0120] In some preferred embodiments, the molar ratio of the carboxylic acid ester, catalyst, base to ethanol is 1:0.0001:0.0001:10N1:0.05:0.0515:500.

[0121] In some preferred embodiments, the temperature of the reduction reaction is 50 - 180 °C, preferably 80 - 150 °C.

[0122] In some preferred embodiments, the time of the reduction reaction is 1 - 120 h.

[0123] In some preferred embodiments, the base may include any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, lithium tert-butoxide, potassium ethoxide, sodium ethoxide, lithium ethoxide, potassium methoxide, sodium methoxide, sodium hydride, potassium hydride, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, etc., but is not limited thereto.

[0124] In some preferred embodiments, the solvent may include any one or a combination of two or more of methanol, ethanol, n-propanol, isopropanol, benzene, toluene, xylene, mesitylene, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, methyl cyclopentyl ether, cyclohexane, heptane, etc., but is not limited thereto.

[0125] In summary, in the specific atmosphere and under the catalysis of the manganese complex, the present invention heats and reduces alkyl carboxylic acid esters, aryl carboxylic acid esters, oils and fats, and polyesters in ethanol to alcohol compounds, which can not only realize the preparation of a variety of fine chemicals, but also realize the high-value conversion of waste polyester plastics, and does not require high-pressure reaction equipment, has simple operation, and has important application prospects. The present invention proposes to use ethanol as a reducing agent, which has a wide source, is renewable, has no pollutants, and has excellent chemoselectivity.

[0126] The following further explains the technical solutions of the present invention in conjunction with several preferred embodiments. It is easy for those skilled in the art to understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. However, it is easy for those skilled in the art to understand that the specific material ratios, process conditions and their results described in the embodiments are only used to illustrate the present invention and should not and will not limit the present invention described in detail in the claims.

[0127] The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0128] The synthesis of the tridentate pincer manganese complex [Mn]-1 used in the following Examples 1 - 14 is as follows:

[0129]

[0130] The specific steps are as follows:

[0131] Under nitrogen protection, 8-fluoroquinaldine (5.3 g, 33.0 mmol), selenium dioxide (7.3 g, 66.0 mmol) and 1,4-dioxane (60 mL) were added to a reaction flask, and the temperature was raised to 80 °C for reaction for 4 hours. After cooling, filtration was carried out under suction and the mixture was concentrated. Column chromatography was performed to obtain S-2 (4.7 g, yield 81%).

[0132] Under nitrogen protection, S-2 (4.9 g, 28.0 mmol), cyclohexylamine (3.1 g, 30.8 mmol) and toluene (25 mL) were added to a reaction flask and stirred at room temperature for 12 hours. The crude product obtained after concentrating the solvent was dissolved in methanol (60 mL). NaBH4 (1.3 g, 33.6 mmol) was added in batches and stirred for 4 hours. Subsequently, the reaction was quenched with saturated ammonium chloride solution. After concentrating to remove the solvent, extraction was carried out with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated to obtain a crude product. Subsequently, it was dissolved in dichloromethane (30 mL), DMAP (341.6 mg, 2.8 mmol) and Boc2O (9.2 g, 42.0 mmol) were added and reacted at room temperature for 12 hours. Subsequently, the reaction was quenched with saturated ammonium chloride, concentrated and column chromatography was performed to obtain S-3 (8.6 g, yield 86%).

[0133] Under nitrogen protection, Ph2PH (4.0 g, 21.5 mmol) and tetrahydrofuran (40 mL) were added to a reaction flask, cooled to -78 °C, n-butyllithium (8.6 mL, 21.5 mmol) was added, then the temperature was raised to room temperature and stirred for 1 hour, then cooled to -78 °C again, and a THF (10 mL) solution of the above S-3 was added, and then the temperature was raised to 60 °C for reaction for 12 hours. After the reaction was completed, the solvent was concentrated, and column chromatography was performed to obtain a white solid S-4 (8.0 g, yield 71%).

[0134] Under nitrogen protection, S-4 (315 mg, 0.6 mmol) and dichloromethane (5 mL) were added to a reaction flask, then trifluoroacetic acid (1 mL) was added and reacted at room temperature for 4 hours. After concentration, the solvent and the excess acid were removed, and it was alkalized with NaOH (aq. 2M solution). Subsequently, extraction was carried out with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated to remove the solvent to obtain a crude product which was directly used for the next step of the reaction.

[0135] Under nitrogen protection, the crude product of the previous step was dissolved in THF (5 mL) and transferred into a reaction flask. The metal manganese catalyst precursor Mn(CO)5Br (138 mg, 0.5 mmol) was added, and the mixture was heated to 70 °C and reacted for 12 hours. After the reaction, the temperature was cooled to room temperature, the solvent was dried under reduced pressure, the reaction flask was transferred into a glove box, washed with diethyl ether, centrifuged, and concentrated to obtain an orange-red solid [Mn]-1 (295.3 mg, yield 96%), which is a novel tridentate pincer manganese complex.

[0136] The inventors of this case also characterized the orange-red solid [Mn]-1 by NMR, high-resolution mass spectrometry, etc. The data are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.26 (s, 1H), 8.13 - 8.05 (m, 4H), 7.76 (s, 1H), 7.49 (br, 1H), 7.40 (s, 3H), 7.27 (br, 3H), 7.20 - 7.16 (m, 2H), 4.39 (s, 2H), 4.21 (br, 1H), 2.91 - 2.86 (m, 1H), 2.26 - 2.23 (m, 1H), 2.19 - 2.16 (m, 1H), 1.92 - 1.80 (m, 4H), 1.72 - 1.68 (m, 1H), 1.39 - 1.27 (m, 3H); 13 C NMR (151 MHz, CDCl3 / CD3OD) δ 231.7, 230.4, 165.9, 161.8, 152.4 (d, J = 22.2 Hz), 137.6 (d, J = 27.3 Hz), 136.9, 134.8 (d, J = 23.6 Hz), 134.8 (d, J = 9.8 Hz), 133.2, 132.9, 132.5, 131.2 (d, J = 10.3 Hz), 130.9, 130.0 (d, J = 2.4 Hz), 129.1, 128.6, 128.1 (d, J = 9.1 Hz), 127.9 (d, J = 9.7 Hz), 127.5 (d, J = 4.8 Hz), 120.2, 119.0, 62.8 (m), 59.4, 57.8, 32.2 (d, J = 45.9 Hz), 25.5 (m); 31 P NMR (162 MHz, CDCl3) δ 85.5. HRMS (ESI) calcd. for MnC 30 H 29 N2O2P[M - Br]: 535.1347, found: 535.1337. IR (vCO) = 1906.6, 1824.4 cm- 1 .

[0137] Example 1

[0138] The manganese complex represented by formula (I) is used as a catalyst to transfer and degrade polyester:

[0139]

[0140] In a nitrogen atmosphere glove box, manganese catalyst (0.5 mol%), potassium tert-butoxide (4.0 mol%) and ethanol (1.0 mL) were added to a glass sealed reaction tube, and PET (0.3 mmol) was added after stirring for 10 minutes. The reaction tube was placed in an oil bath and heated at 100 ° C. and reacted for 24 hours under magnetic stirring. After the reaction was completed, internal standard n-dodecane was added, and the yield of the product 4-(hydroxymethyl) ethyl benzoate was 89% and the yield of terephthalic acid methanol was 10% by GC monitoring.

[0141] like Figure 1 and Figure 2 As shown in Figure 2, they are the hydrogen and carbon nuclear magnetic resonance spectra of ethyl 4-(hydroxymethyl)benzoate. Figure 3 and Figure 4 Shown are the hydrogen and carbon nuclear magnetic resonance spectra of p-phenylenediol, respectively.

[0142] Example 2-14

[0143]

[0144] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-1 (0.5 mol%), alkali (4.0 mol%) and ethanol (1.0 mL) were added to a glass sealed reaction tube, and PET (0.3 mmol) was added after stirring for 10 minutes. The reaction tube was placed in an oil bath and heated at 100 ° C. and reacted for 24 hours under magnetic stirring. After the reaction was completed, internal standard n-dodecane was added and monitored by GC. The yields of the products 4-(hydroxymethyl) ethyl benzoate and p-phenylenediol are shown in Table 1.

[0145] Table 1 Yields of product 4-(hydroxymethyl) ethyl benzoate and p-phenylenediol in Examples 2-14

[0146]

[0147]

[0148] The synthesis methods of several manganese complexes used in the following Examples 15-24 are as follows:

[0149] Compared with the synthesis method of product [Mn]-1, the preparation method of [Mn]-2 is different in that cyclohexylamine is replaced by benzylamine. The structure of the obtained product [Mn]-2 is:

[0150]

[0151] The inventors of this case also characterized the product by NMR, high-resolution, etc. The data are as follows: 1 H NMR(400MHz, CDCl3)δ8.20(d, J = 2.8Hz, 1H), 8.10 - 8.01(m, 4H), 7.74(s, 1H), 7.44 - 7.35(m, 8H), 7.31 - 7.29(m, 4H), 7.25 - 7.20(m, 2H), 4.90(d, J = 13.6Hz, 1H), 4.44(s, 1H), 4.23 - 4.19(m, 1H), 4.11 - 3.98(m, 2H); 13 C NMR(101MHz, CD2Cl2)δ231.2, 229.5(d, J = 17.8Hz), 161.7(d, J = 3.6Hz), 152.5(d, J = 22.2Hz), 138.3, 138.0, 137.3, 137.1(d, J = 3.9Hz), 136.8, 134.9(d, J = 10.1Hz), 133.4, 133.2, 131.5(d, J = 10.7Hz), 130.9, 130.2(d, J = 2.3Hz), 129.3, 129.2, 128.9, 128.5, 128.3(d, J = 9.7Hz), 128.1(d, J = 9.8Hz), 127.7(d, J = 4.5Hz), 118.8, 61.4, 59.2; 31 P NMR(162MHz, CDCl3)δ83.7. HRMS(ESI) calcd. for MnC 31 H 25 N2O2P[M - Br]: 543.1034, found: 543.1018. IR(vCO) = 1923, 1843cm -1 .

[0152] Compared with the synthesis method of the product [Mn] - 1, the preparation of [Mn] - 3 is different in that cyclohexylamine is replaced by isopropylamine. The structural formula of the finally obtained tridentate pincer - shaped manganese complex [Mn] - 3 is:

[0153]

[0154] The synthesis method of manganese complex [Mn] - 4 is as follows:

[0155]

[0156] Under nitrogen protection, S-2 (1.75 g, 10 mmol) prepared in the example and THF (20 mL) were added to a reaction flask, cooled to -78 °C, and CH3MgBr (12 mmol) was added. Subsequently, the mixture was stirred at room temperature for 3 hours. The reaction was quenched by adding water, the solvent was removed by concentration, and the residue was extracted with ethyl acetate. The organic phases were combined, dried, concentrated, and purified by column chromatography to obtain S-6 (1.7 g, yield 89%).

[0157] Under nitrogen protection, S-6 (1.6 g, 8.5 mmol), pyridine (0.53 mmol, 6 mol%), and dichloromethane (30 mL) were added to a reaction flask. After cooling to 0 °C, thionyl chloride (0.8 mL, 10.6 mmol) was added, and then the mixture was stirred at room temperature for 3 hours. After the reaction was completed, the reaction was quenched with water, and the mixture was alkalized with saturated potassium carbonate solution. Subsequently, it was extracted with ethyl acetate, the organic phases were combined, dried, and the solvent was removed by concentration to obtain the crude product S-7, which was directly used for the next step of the reaction.

[0158] Under nitrogen protection, a mixture of NaI (36.0 mg, 0.24 mmol), K2CO3 (662.4 mg, 4.8 mmol), cyclohexylamine (712.8 mg, 7.2 mmol), and CH3CN (10 mL) was added to a Schlenk flask, and then a CH3CN solution (10 mL) of S-7 (501.6 mg, 2.4 mmol) was added. The mixture was heated to 80 °C and stirred for 12 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the resulting residue was purified by column chromatography to obtain a yellow oil S-8 (498.8 mg, yield 76%).

[0159] Under nitrogen protection, S-8 (272 mg, 1.0 mmol) was dissolved in dichloromethane (5 mL). DMAP (12.2 mg, 0.1 mmol) and Boc2O (324 mg, 1.5 mmol) were added to the reaction mixture, and the mixture was stirred at room temperature for 12 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the resulting residue was purified by silica gel column chromatography to obtain a yellow oil S-9 (206.9 mg, yield 56%).

[0160] Under nitrogen protection, a mixture of diphenylphosphine (133.9 mg, 0.72 mmol) and THF (3 mL) was added to a Schlenk flask. Then, n-butyllithium (0.3 mL, 0.72 mmol) was added to the mixture at -78 °C, and the temperature was slowly raised to room temperature. The reaction mixture was stirred at room temperature for another 1 hour. Then, a THF solution (2 mL) of S-9 was added at -78 °C, and the reaction mixture was stirred at 60 °C for 12 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the resulting residue was purified by silica gel column chromatography to obtain a yellow oil S-10 (167.7 mg, yield 64%).

[0161] Under nitrogen protection, Mn(CO)5Br (69 mg, 0.25 mmol), S-10 (131.4 mg, 0.3 mmol) and THF (5 mL) were added to a 25 mL Schlenk flask. The reaction mixture was stirred at 70 °C for 12 hours. The solvent was removed under vacuum, and the resulting residue was washed several times with n-hexane and diethyl ether. After simple centrifugation and concentration, an orange-red solid [Mn]-4 (129.8 mg, yield 83%) was obtained.

[0162] The inventors of this case also characterized the orange-red solid [Mn]-4 by NMR, high-resolution, etc., and the data are as follows: 1 H NMR (600 MHz, CD2Cl2) δ 8.38 - 8.34 (m, 1H), 8.18 - 8.10 (m, 2H), 8.04 - 8.01 (m, 0.74H), 7.97 - 7.94 (m, 1.2H), 7.84 - 7.79 (m, 1H), 7.55 (d, J = 8.4 Hz, 0.66H), 7.49 (d, J = 8.4 Hz, 0.43H), 7.43 - 7.38 (m, 3H), 7.31 - 7.23 (m, 5H), 4.84 - 4.81 (m, 0.49H), 4.57 - 4.49 (m, 1H), 4.08 (d, J = 10.2 Hz, 0.69H), 3.69 - 3.67 (m, 1H), 3.00 - 2.96 (m, 0.73H), 2.80 - 2.76 (m, 0.5H), 2.47 (d, J = 12.6 Hz, 0.47H), 2.31 - 2.24 (m, 0.77H), 2.04 - 2.00 (m, 1H), 1.96 - 1.86 (m, 2H), 1.79 - 1.78 (m, 2H), 1.63 - 1.62 (m, 1H), 1.54 (br, 1H), 1.41 - 1.35 (m, 2H), 1.32 - 1.27 (m, 2H); 1313C NMR (151 MHz, CD2Cl2) δ 232.1, 231.9, 167.4 (d, J = 3.0 Hz), 167.0 (d, J = 3.3 Hz), 152.7 (d, J = 22.3 Hz), 152.6 (d, J = 22.7 Hz), 138.4, 138.1, 138.0, 137.8, 137.5 (d, J = 4.2 Hz), 137.3 (d, J = 4.3 Hz), 136.7 (d, J = 27.5 Hz), 136.6 (d, J = 27.3 Hz), 135.3 (d, J = 9.7 Hz), 135.0 (d, J = 9.2 Hz), 134.7, 134.5, 134.1, 133.8, 131.9 (d, J = 10.3 Hz), 131.7 (d, J = 10.1 Hz), 131.4, 130.4, 130.2, 129.5, 128.6 (m), 128.1 (m), 127.9 (d, J = 4.7 Hz), 127.8 (d, J = 4.7 Hz), 120.0, 119.3, 68.2, 65.8, 63.3, 60.4 (d, J = 8.8 Hz), 36.0, 34.0, 33.7, 32.2, 32.0, 26.3, 26.0, 23.1, 19.7, 19.5, 14.3; 31 31P NMR (162 MHz, DMSO-d6) δ 84.4, 84.0. HRMS (ESI) calcd. for MnC 31 H 31 N2O2P[M-Br]: 549.1504, found: 549.1479. IR (vCO) = 1919.9, 1842.6 cm -1 .

[0163] The synthesis method of manganese complex [Mn]-6 is as follows:

[0164]

[0165] Under nitrogen protection, S-2 (1.8 g, 10.0 mmol) prepared in Example 1, cyclohexylamine (1.1 g, 11.0 mmol) and toluene (15 mL) were added to a reaction flask and stirred at room temperature for 12 hours. The crude product obtained after concentrating the solvent was dissolved in methanol (15 mL). NaBH4 (456 mg, 12.0 mmol) was added in batches and stirred for 4 hours. Subsequently, the reaction was quenched with saturated ammonium chloride solution. After concentrating to remove the solvent, it was extracted with ethyl acetate. The combined organic phases were dried over anhydrous sodium sulfate and concentrated. The resulting residue was purified by silica gel column chromatography to obtain a yellow oil, S-11 (1.9 g, yield 75%).

[0166] Under nitrogen protection, dissolve S-11 (1.7 g, 6.5 mmol) in THF (15 mL). Then add NaHH (312 mg, 13.0 mmol) to the reaction mixture at room temperature and stir for 1 hour. Subsequently, add CH3I (1.0 g, 7.2 mmol) and continue stirring for 12 hours. After the reaction is completed, quench with water, remove the solvent, and extract the residue with ethyl acetate. Combine the organic phases, dry, remove the solvent under reduced pressure, and purify the obtained residue by silica gel column chromatography to obtain a yellow oil, S-12 (1.1 g, yield 65%).

[0167] Under nitrogen protection, add Ph2PH (186.2 mg, 1.0 mmol) and tetrahydrofuran (5 mL) to a reaction flask, cool down to -78 °C, add n-butyllithium (0.4 mL, 1.0 mmol), then raise the temperature to room temperature and stir for 1 hour. Then cool down to -78 °C again, and add the THF (10 mL) solution of the above S-12. Subsequently, raise the temperature to 60 °C and react for 12 hours. After the reaction is completed, concentrate the solvent and perform column chromatography to obtain S-13 (409.2 mg, yield 93%).

[0168] Under nitrogen protection, dissolve S-13 (219 mg, 0.5 mmol) in THF (5 mL), add the metal manganese catalyst precursor Mn(CO)5Br (123 mg, 0.45 mmol), and heat to 70 °C and react for 12 hours. After the reaction is completed, cool down to room temperature, drain the solvent, transfer the reaction flask into a glove box, add ether for washing, centrifuge, and concentrate to obtain an orange-red solid, [Mn]-6 (260.0 mg, yield 90%).

[0169] The inventors of this case also characterized the orange-red solid [Mn]-6 by NMR, high-resolution, etc. The data are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.28 (d, J = 6.8 Hz, 1H), 8.11 (s, 1H), 7.78 - 7.75 (m, 3H), 7.52 - 7.43 (m, 3H), 7.33 (s, 7H), 5.00 (s, 0.83H), 4.59 (s, 0.25H), 3.86 (s, 1H), 3.66 (s, 1H), 2.99 - 2.96 (m, 1H), 2.87 (s, 0.48H), 2.56 (s, 2.61H), 1.96 - 1.80 (m, 3H), 1.72 - 1.56 (m, 2H), 1.50 - 1.22 (m, 4H); 1313C NMR (101 MHz, CDCl3) δ 231.9 (d, J = 21.8 Hz), 229.7 (d, J = 26.3 Hz), 164.7 (d, J = 3.5 Hz), 153.1 (d, J = 22.1 Hz), 153.0 (d, J = 20.9 Hz), 137.3, 136.8 (d, J = 4.3 Hz), 136.2, 135.7 (d, J = 3.4 Hz), 135.3, 135.0, 134.7, 134.1 (d, J = 9.2 Hz), 133.8 (d, J = 9.4 Hz), 131.9 (d, J = 9.8 Hz), 131.0, 129.5 (d, J = 2.4 Hz), 129.4 (d, J = 2.2 Hz), 128.1 (m), 127.2 (d, J = 4.4 Hz), 120.3, 119.1, 71.1, 66.4, 65.3, 63.9, 44.9, 33.4, 31.6 (d, J = 5.2 Hz), 27.7, 26.4, 26.2, 26.0 (m), 25.5, 25.0, 22.7, 14.1; 31 31P NMR (162 MHz, CDCl3) δ 92.5, 90.0. HRMS (ESI) calcd. for MnC 31 H 31 N2O2P[M - Br]: 549.1504, found: 549.1505. IR (νCO) = 1919.7, 1843.3 cm -1 .

[0170] Examples 15 - 24

[0171]

[0172] In a nitrogen - atmosphere glove box, manganese catalyst (0.5 mol%), potassium tert - butoxide (4.0 mol%) and ethanol (1.0 mL) were added to a glass - sealed reaction tube. After stirring for 10 minutes, PET (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating, and the reaction was carried out under magnetic stirring for 24 h. After the reaction was completed, internal standard n - dodecane was added, and the yields of the products ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol were monitored by GC as shown in Table 2.

[0173] Table 2 Yields of ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol in Examples 15 - 24

[0174]

[0175]

[0176]

[0177] Examples 25 - 34

[0178]

[0179] In a nitrogen - atmosphere glove box, manganese catalyst [Mn]-1 (x mol%), potassium tert - butoxide (y mol%), and ethanol (1.0 mL) were added to a glass - sealed reaction tube. After stirring for 10 minutes, PET (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating, and the reaction was carried out for a specific time under magnetic stirring. After the reaction was completed, internal standard n - dodecane was added, and the yields of the products ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol were monitored by GC as shown in Table 3.

[0180] Table 3 Yields of ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol in Examples 25 - 34

[0181]

[0182] Examples 35 - 39

[0183]

[0184] In a nitrogen - atmosphere glove box, manganese catalyst [Mn]-1 (1 mol%), potassium tert - butoxide (6 mol%), and ethanol (x mL) were added to a glass - sealed reaction tube. After stirring for 10 minutes, PET (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating, and the reaction was carried out for a specific time under magnetic stirring. After the reaction was completed, internal standard n - dodecane was added, and the yields of the products ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol were monitored by GC as shown in Table 4.

[0185] Table 4 Yields of ethyl 4 - (hydroxymethyl)benzoate and p - xylyl alcohol in Examples 35 - 39

[0186]

[0187] Example 40

[0188]

[0189] Under an argon atmosphere, manganese catalyst [Mn]-2 (1 mol%), potassium tert - butoxide (6 mol%), and ethanol (1 mL) were added to a glass - sealed reaction tube. After stirring for 10 minutes, polyethylene terephthalate PET (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating, and the reaction was carried out for 48 h under magnetic stirring. After the reaction was completed, internal standard n - dodecane was added, and the yield of the product ethyl 4 - (hydroxymethyl)benzoate was 83%, and the yield of p - xylyl alcohol was 14% as monitored by GC.

[0190] Example 41

[0191]

[0192] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-2 (1 mol%), potassium tert-butoxide (6 mol%), and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, polyethylene terephthalate PET (0.3 mmol) was added. The reaction tube was degassed by freezing, filled with H2 (1 bar), and then placed in an oil bath at 100 °C for heating. The reaction was carried out under magnetic stirring for 48 h. After the reaction was completed, internal standard n-dodecane was added. By GC monitoring, the yield of ethyl 4-(hydroxymethyl)benzoate was 33%, and the yield of terephthalyl alcohol was 65%.

[0193] Example 42

[0194]

[0195] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-2 (0.5 mol%), potassium tert-butoxide (4 mol%), and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, polybutylene terephthalate PBT (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating. The reaction was carried out under magnetic stirring for 48 h. After the reaction was completed, internal standard n-dodecane was added. By GC monitoring, the yield of ethyl 4-(hydroxymethyl)benzoate was 72%.

[0196] Example 43

[0197]

[0198] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-2 (3 mol%), potassium tert-butoxide (12 mol%), and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, polybutylene terephthalate PBT (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C for heating. The reaction was carried out under magnetic stirring for 72 h. After the reaction was completed, internal standard n-dodecane was added. By GC monitoring, the yield of terephthalyl alcohol was 69%.

[0199] Example 44

[0200]

[0201] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-2 (3 mol%), potassium tert-butoxide (12 mol%) and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, polybutylene succinate PBS (0.3 mmol) was added. The reaction tube was placed in an oil bath at 100 °C and heated, and the reaction was carried out for 48 h under magnetic stirring. After the reaction was completed, internal standard n-dodecane was added, and the yield of the product 1,4-butanediol was 74% by GC monitoring.

[0202] Example 45

[0203]

[0204] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-2 (3 mol%), potassium tert-butoxide (12 mol%) and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, polylactic acid PLA (0.5 mmol) was added. The reaction tube was placed in an oil bath at 100 °C and heated, and the reaction was carried out for 48 h under magnetic stirring. After the reaction was completed, internal standard n-dodecane was added, and the yield of the product 1,2-propanediol was 81% by GC monitoring.

[0205] Examples 46 - 61

[0206]

[0207] In a nitrogen atmosphere glove box, manganese catalyst [Mn]-3 (2.5 mol%), potassium tert-butoxide (15 mol%) and ethanol (1.5 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, oil (100 mg) was added. The reaction tube was placed in an oil bath at 100 °C and heated, and the reaction was carried out for 48 h under magnetic stirring. After the reaction was completed, alcohol compounds were obtained by column chromatography, and the proportion of mixed alcohols was qualitatively and quantitatively analyzed by GC. The results are shown in Table 5.

[0208] Table 5 Qualitative and quantitative analysis results of Examples 46 - 61

[0209]

[0210]

[0211] Figure 5 1H NMR spectrum of oleyl alcohol. Figure 6 、 Figure 7 、 Figure 8 and Figure 9 are the gas chromatograms of corn oil, soybean oil, sweet almond oil, and blended oil after the reaction, respectively.

[0212] Examples 62 - 68

[0213]

[0214] In a nitrogen atmosphere glove box, the manganese catalyst [Mn]-3 (1 mol%), potassium tert-butoxide (5 mol%) and ethanol (1 mL) were added to a glass-sealed reaction tube. After stirring for 10 minutes, methyl oleate (0.5 mmol) was added. The reaction tube was placed in an oil bath and heated, and the reaction was carried out for 24 h under magnetic stirring. After the reaction was completed, internal standard n-dodecane was added, and the yield of the product oleyl alcohol was determined by GC. The results are shown in Table 6.

[0215] Table 6 Yield results of Examples 62-68

[0216] Example Reaction Temperature (°C) Yield of Oleyl Alcohol (%) Example 62 50 20 Example 63 80 74 Example 64 100 92 Example 65 110 93 Example 66 120 88 Example 67 150 63 Example 68 180 47

[0217] Through the above examples and application examples, it can be found that the reaction of reducing carboxylic acid esters with ethanol using the manganese complex as a catalyst obtained by the above technical solution of the present invention is efficient, simple to operate, has a wide application range, and has good application prospects.

[0218] It should be understood that the above examples are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A catalyst for the reduction of carboxylic acid esters with ethanol, characterized in that, The catalyst includes a manganese complex, and the manganese complex has a structure shown in formula (I): Among them, R 1 is selected from C1 to C 20 alkyl or aryl, R 2 , R 3 and R 4 are selected from H, C1 to C 20 alkyl or aryl.

2. A method for reducing carboxylic acid esters with ethanol, characterized in that, Including: In an atmosphere of hydrogen, nitrogen or an inert gas, a reaction system containing a carboxylic acid ester, a catalyst, a base, ethanol as a reducing agent and a solvent is subjected to a reduction reaction, so that the carboxylic acid ester is reduced to an alcohol compound; The catalyst includes a manganese complex, and the manganese complex has a structure shown in formula (I): Among them, R 1 is selected from C1-C 20 alkyl or aryl, R 2 , R 3 and R 4 are selected from H, C1-C 20 alkyl or aryl.

3. The method according to claim 2, characterized in that, Including: A reaction system containing a carboxylic acid ester, a catalyst, a base, ethanol and a solvent is subjected to a reduction reaction under a temperature condition of above 50 °C.

4. The method according to claim 2, wherein: The inert gas includes argon.

5. The method according to claim 2, wherein The structure of the carboxylic acid ester is shown in formula (II), formula (III) or formula (IV): Among them, R and R' are each independently selected from a fatty group containing C1-C 40 or an aryl group containing C6-C 60 , and n is 1 to 500.

6. The method according to claim 2, wherein: The carboxylic acid ester is derived from a beverage bottle, outer packaging or used clothing containing polyethylene terephthalate.

7. The method according to claim 2, wherein: The molar ratio of the carboxylic acid ester, the catalyst, the base to ethanol is 1:0.0001:0.0001:10 to 1:0.05:0.0515:

500.

8. The method according to claim 2 or 3, characterized in that: The temperature of the reduction reaction is 50-180 °C, preferably 80-150 °C; and / or, the time of the reduction reaction is 1-120 h.

9. The method according to claim 2, wherein: The base includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, lithium tert-butoxide, potassium ethoxide, sodium ethoxide, lithium ethoxide, potassium methoxide, sodium methoxide, sodium hydride, potassium hydride, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide.

10. The method according to claim 2, wherein: The solvent includes any one or a combination of two or more of methanol, ethanol, n-propanol, isopropanol, benzene, toluene, xylene, mesitylene, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, methyl cyclopentyl ether, cyclohexane, heptane.

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